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Notes on the Revision of the Genus Mopsechiniscus (Tardigrada)
Zool. Anz. 240 (2001): 299–308 © by Urban & Fischer Verlag http://www.urbanfischer.de/journals/zoolanz
Notes on the Revision of the Genus Mopsechiniscus (Tardigrada)* Hieronymus DASTYCH Zoologisches Institut und Zoologisches Museum der Universität Hamburg, Hamburg, Germany Abstract. A redescription of the semi-terrestrial tardigrade genus Mopsechiniscus from the Southern Hemisphere and identification keys for its members, including instars, are provided. Revised notes on biology, distribution, and phylogeny of the genus are presented. Key words. Tardigrada, Mopsechiniscus redescription.
1. INTRODUCTION While working on tardigrades from the Crozet Islands, several specimens belonging to the rarely reported genus Mopsechiniscus Du Bois-Reymond Marcus, of the ancient semi-terrestrial family Echiniscídae were found. During identification of this material, which turned out to represent a new species (DASTYCH 1999b), it was noticed that there was considerable taxonomic confusion surrounding Mopsechiniscus, in so far as the interpretation of some morphological characters of M. imberbis (Richters, 1908), the type species of the genus, is concerned. It became evident that almost all workers, who had dealt with this genus, including its author, misidentified M. imberbis for various congeners, thus significantly contributing to the confusion (see DASTYCH 1999a for details). To clarify this and other taxonomic questions, a redescription of M. imberbis and M. granulosus MIHEL CI ˇ Cˇ , 1967, which also represents another most often misidentified congener, was provided by DASTYCH (1999a, 2000). Furthermore, a re-examination of specimens from Venezuela reported by GRIGARICK et al. 1983, which allegedly represent the northernmost occurrence of M. imberbis, brought to light another wrong identification, as this material belonged to an undescribed species (DASTYCH 1999c).
*
Contribution to the 8th International Symposium on Tardigrada, Copenhagen, Denmark, 30 July–5 August 2000.
This paper summarizes and discusses new and verified data on morphology of particular members of Mopsechiniscus and their variability, and includes information on distribution, biology and phylogeny of the genus, updates its description and provides identification keys for adults and all known instars. The taxonomic history of Mopsechiniscus is not dealt with as it has been presented elsewhere (DASTYCH 1999a).
2. MATERIAL AND METHODS The paper is based on Mopsechiniscus material from Venezuela, Argentina, Chile, Sub-Antarctic South Georgia, Crozet Islands and Tasmania, including an unidentified individual of Mopsechiniscus from Tierra del Fuego (for the latter see DASTYCH 1999c). Recently some aspects of that material have been presented in a number of papers which are mostly of a revisory character (DASTYCH 1999a, b, c, 2000). The examined specimens are deposited in the Zoologisches Museum Hamburg, British Antarctic Survey (Cambridge), R. M. Bohart Museum (Davis, California), Zoologisk Museum (Copenhagen), Universidad Nacional y Museo (La Plata), Museo Civico de Storia Naturale (Verona), Natal Museum (Pietermaritzburg), and in the private collection of Mr. T. Meier (Oslo). All material is mounted on microscope slides in polyvinyl-lactophenol, Hoyer’s or Faure’s medium and was examined in phase and interference contrast. Photomicrographs were taken with a ZEISS “Axiomat” and “Fotomikroskop III”. Cuticular body projections, depending on their length and shape are alternately being named as cirri, appendages, spines or teeth. The “sp index” (= shoulder plate’ index) expresses the ratio between the length of the considered structure and the length of shoulder plate (see DASTYCH 1999c). 0044-5231/01/240/03–04-299 $ 15.00/0
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List of abbreviations A B bc bp C cs c1 c2 D D2 e ec ex fd i in ic mc m2 m1d m2d n np pl 1 ps psd s sp su tp I, II
– lateral appendage (cirrus) A – lateral appendage B on platelet 1 (at the shoulder plate) – claw basal cusp – leg basal plate – lateral appendage (spine) C at/on platelet 2 (paired plates I) – claw spur – primary clava (= clava) – secondary clava (= cephalic papilla) – lateral appendage (cirrus) D at/on platelet 3 (paired plates II) – dorsal appendage on paired plate II – eye spot – external cusion on leg – external claw – lateral folds on median plate 2 – triangular insertion of the paired plate II – internal claw – internal cushion on leg – mouth cone – median plate 2 – dorsal prtojection on median plate 1 – dorsal projections on median plate 2 – notch – neck plate – platelet 1 – pseudosegmental plate – projections on pseudosegmental plate – leg spur – shoulder plate – subcephalic median plate – terminal plate – the first and the second paired plate.
3. RESULTS Family: Echiniscidae Thulin, 1928 Mopsechiniscus Du Bois-Reymond Marcus Mopsechiniscus Du Bois-Reymond Marcus, 1944: 6 Diagnosis: Echiniscidae with paired pseudosegmental plate. Head without external and internal sensory cirri; prominent dome-shaped cephalic papillae (= secondary clavae). Posterior margin of median plate m2 with a fold. Cirrophore and flagellum of cirrus A fused, without discernible border. Feet slightly asymmetrical due to presence of differently sized cusp- and cushionlike structures on lateral sides of the proximal part of each leg. Two-clawed instars with the same or greater number of trunk appendages compared to adults. Type species: Echiniscus imberbis Richters, 1908, by original designation. Note: The original description of the genus and its redescription (DU BOIS-REYMOND MARCUS 1944; KRI-
1987) are in fact based on an undescribed species of Mopsechiniscus from Brasil and M. granulosus from Argentina. These taxa were at that time misidentified as M. imberbis, the type species (see DASTYCH 1999a for details). Type locality: Sub-Antarctic South Georgia. Other species: M. granulosus Mihelˇciˇc, 1967, M. tasmanicus Dastych & Moscal, 1992, M. frenoti Dastych, 1999, M. schusteri Dastych, 1999, as well as two undescribed species, one of which was reported by DU BOIS-REYMOND MARCUS (1944) from Brazil under the name M. imberbis (here referred to as Mopsechiniscus sp. 1) and the other one from Tierra del Fuego (comp. DASTYCH 1999c), referred to as M. sp. 2. Etymology: Originally not explained. The German prefix “Mops” (= pug or pug-faced) in the generic name may refer to the peculiar appearance of the animal head (see Fig. 7), resulting from the presence of distinct head papillae, and the lack of both pairs of sensory cirri. STENSEN
Amended description Adults Body yellow-reddish to dark-red, dark-brown eye-dots present, not discernible in Mopsechiniscus sp. 2 (see DASTYCH 1999c). Dorsal plates well formed; plates and lateral area between them with a sculptured (‘granulated’) cuticle (Figs. 1, 2). Only M. imberbis with small male genital plates; no other ventral trunk plates present. Head plate with a facet formed by two oval, slightly depressed and closely placed cephalic shields. Facet nearly always well developed in M. imberbis and M. tasmanicus, forming within its posterior part a kind of W-like pattern, but is poorly marked (Figs. 1, 4) or not at all in other congeners. Subcephalic plate usually indistinctly defined, often limited only by two lateral, short and poorly marked cuticular thickenings. Plate, mostly covered with minute, closely placed punctation, has the shape of a weakly marked, median and inverted triangle-like (M. imberbis: Fig. 7: su, M. granulosus) or is a poorly discernible, more square-like structure (M. frenoti). This plate may also be represented by a pair of indistinct oval shields (M. tasmanicus) or can be absent. Neck plate (np) markedly long and distinct, shoulder plate (sp) and paired trunk plates I and II of similar length, pseudosegmental plate (Fig. 1: ps) about onethird shorter than the plates II, terminal plate (tp) median sized, mostly with a pair of long, more or less distinctly marked notches (= incisions; Fig. 1: n). M. imberbis has a sp plate with a more or less distinct, vertically directed keel. In M. granulosus the middle part of the posterior edge of tp plate is often almost parallel to the anterior edge or may even curve towards it.
Revisionary notes on Mopsechiniscus (Tardigrada)
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Figs. 1–3. Mopsechiniscus schusteri Dastych, 1– female, 2 – subadult; Mopsechiniscus frenoti Dastych, 3 – male (All in dorso-lateral view. Figs. 1, 3: holotype, Fig. 2: paratype. Scale bar: 30 µm. Abbreviations explained in text).
Three median plates (m1–3) present, first and third whole, second divided into three-pieces (Figs. 1–4). Plate m1 large and triangular, its apex directed posteriorly and often broadly rounded (M. schusteri: Figs. 1, 2). Plate m2 trapezoidal in its larger anterior part, which is characteristically folded over anterior margin of paired plates II. Second piece of plate m2 shaped like a narrow transverse belt is tucked under the fold and the belt bordering with a small, triangular insertion in the anterior margin of paired plate II. The insertion, a part of the trunk segment III, represents the most posterior part of the plate m2, i.e. its third piece. Lateral edges of plate m2 mostly with two small, usually indistinctly formed but characteristic folds (Figs. 1, 2, 4, 5). Plate m3 the smallest, triangular or rhomboidal in shape (Figs. 1, 5). Each side of dorsal trunk plate with a small, closely placed lateral plate (platelets I–IV), separated from main plate nearly always by a distinct cuticular fold (Figs. 1, 2). A similar fold also limits each platelet posteriorly (Fig. 2: asterisk) and separates it from the closely located base of the leg. Platelet I mostly trapezium-like or in the shape of an irregular polygon (M. schusteri: Figs. 1, 2), platelet apex roundish and
blunt (M. frenoti, M. tasmanicus, some M. granulosus) or terminated in a short distinct tooth (= projection B: in M. imberbis, some M. granulosus). Platelets II and III smaller, more elongated, with poorly defined lateral edges. Posterior parts of these platelets associated (terminated) with lateral appendages C and D, which are species-specifically shaped (e.g. Figs. 1–3). Platelet IV, formed as a more or less distinct lateral lobe of plate tp, located between notch and anteriolateral edge of plate (Fig. 2), is not present in M. frenoti. Head segment ventrally with large, wide based mouth cone and a pair of prominent secondary clavae (= cephalic papillae, c2: Figs. 3, 7). These are oval or roundish and slightly flattened dome-shaped, more or less larger in males than in females. Internal and external sensory cirri absent. The above combination of characters gives the head of Mopsechiniscus species an unmistakable appearance (Fig. 7). Chaetotaxy (= the arrangement and shape of the body appendages) in Mopsechiniscus, as in other echiniscids, is species-specific. The shape of lateral and dorsal appendages varies from long filamentous cirri to short wide and blunt projections, including intermediate forms (for specific details see DASTYCH & MOSCAL
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1992; DASTYCH 1999a, b, c, 2000). The presence of appendages on median plates is a unique character for Mopsechiniscus species (m2d in adults of M. imberbis and M. frenoti: e.g. Figs. 3, 5 and, additionally, m1d in juveniles of M. granulosus and two-clawed instars of M. schusteri: for the latter see GRIGARICK et al., 1983, p. 67). The appendages mostly have a wide base, that in M. tasmanicus is distinctly sculptured internally (DASTYCH & MOSCAL 1992), such sculpturing not being known in other echiniscids. Cirri A mostly formed as slightly flexible appendages of length varying from extremely long in M. tasmanicus to strikingly short in M. schusteri (Figs. 1, 2). Their cirrophores completely fused with the flagellum base, i.e. without a marked border between. The base of cirri A posteriorly with a small, mostly distinctly formed protecting
cavity for primary clava (= clava: c1). These clavae are directed backward (comp. also RAMAZZOTTI 1962), more or less conical and slightly incurved (Figs. 1–3). The apex of the clavae is roundish. Dorsal plates and adjacent lateral sides of the body, including area between the plates, sculptured with distinct, small hemispherical tubercles (knobs: Figs. 1–5), ≤ 2.7 µm diameter (on average 1–2 µm). The knobs representing modified subcuticular pillars, protrude slightly above the cuticle surface and are more or less widely spaced and evenly distributed. Between the knobs in M. imberbis (and partly in M. schusteri and M. sp. 2) occur tiny, closely spaced and barely visible punctation. In M. frenoti these knobs are relatively closely placed, uniformly distributed and arranged almost hexagonally (Fig. 3), being sometimes connected through thin, hard-
Figs. 4–9. Mopsechiniscus granulosus Mihelciˇ ˇ c, 4 – female, dorsal view; Mopsechiniscus imberbis (Richters), 5 – dorsal plates, 6 – external side od leg II, 7 – body anterior, ventral view (male), 8 – internal side of leg I, 9 – claws of leg IV (Fig. 4: specimen from the Villarica Volcano, Chile, Figs. 5–9: vicinity of Husvik, South Georgia. Scale bar for Fig. 4: 20 µm, Fig. 5: 30 µm, Figs. 6–9: 10 µm).
Revisionary notes on Mopsechiniscus (Tardigrada)
ly visible stripes, similar to those occurring in, e.g. Cornechiniscus cornutus (Richters, 1907). In other Mopsechiniscus spp., particularly M. tasmanicus, the knobs are more sparsely and irregularly spaced. Legs median sized, being longest in M. imberbis and shortest in M. schusteri. Sensory spine on leg I absent, sensory papilla on leg IV present. Legs IV without a fringe of spines. Externally, a strongly sclerotized and elongated basal plate (bp: Fig. 2) below the segmental platelet on the proximal part of each leg, i.e. at leg’s base. This plate distinct on legs I–III, but poorly formed on legs IV. Beneath the basal plate an oval or roundish granulated area. Each foot, i.e. the distal part of a leg, is slightly asymmetric due to presence of two cushion- and cusp-like structures of different size, located on each side of claw row, with internal structure (ic: Fig. 8) slightly larger than external one (ec: Fig. 6). Cushions ec are particularly well formed and largest in M. imberbis. Usually, both external and internal cushions have a dorsal keel, being particularly distinct and usually sharply terminated on ec cushion (Fig. 6). This cushion is cusp- or spur-like; ic is longer and more bar-like. The structures are well developed in M. imberbis, distinct in M. granulosus, but are poorly formed in M. frenoti and M. schusteri. In addition, a cuticular spur occurs between granulated area of the legs and the external cushion (ec). The presence and shape of this structure varies in particular species. In M. imberbis the spur is a distinctly conical, wide based and sharply tipped structure (Fig. 6: s), directed posteriorly which increases in size from I to III leg. On legs IV, however, that spur is only a median sized papilla. In other taxa the spur is smaller, shaped as a round-tipped conical structure or poorly defined papilla and is present on legs III and (mostly) also on legs II. Some specimens of M. schusteri have a trace of the spur also on leg I. In M. tasmanicus, due to the unfavourable positioning of the only two known, slidemounted specimens, such a spur could not be seen. Claws are slender and long (M. imberbis: Figs. 6, 8, 9, partly M. frenoti), shorter and less slender (M. tasmanicus, M. schusteri) or intermediate (M. granulosus). The claws increase slightly in length from leg I to IV, those on leg IV are distinctly (20–30%) longer. External claws (ex) slightly shorter than internal (in) and with an elongated base formed by a well defined basal cusp (bc). Internal claws with poorly formed basal cusp occur in M. tasmanicus and M. frenoti; in other species this cusp is more distinct. External claws smooth, internal ones with a well-defined but moderately sized spur (Fig. 9: cs) placed slightly above the claw base, the spur directed towards the claw base. The space between spur and basal cusp is more oval or even sharp-angled on legs I–III, but more roundish on claw IV (Fig. 9), while in M. tasmanicus it is very small and sharp-angled.
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Juveniles Two-clawed juveniles (‘larvae’) which have been found for four species, i.e. M. sp. 1, M. granulosus, M. schusteri and M. imberbis (DU BOIS-REYMOND MARCUS 1944; RAMAZZOTTI 1962; GRIGARICK et al. 1983; DASTYCH 1999a, respectively), have been mostly recorded under the name of M. imberbis. The morphology of these instars is best, though still incompletely, known in M. granulatus, less well in M. imberbis and only fragmentarily in the two remaining taxa (comp. DASTYCH 1999a, 2000). The ‘larvae’ in Mopsechiniscus are characterized by the most diversified chaetotaxy among all the postembrional stages, i.e. they have the largest number of lateral and dorsal appendages compared to adults. This phenomenon is unique for Mopsechiniscus and is contrary to the trend observed in many other Echiniscidae (RAMAZZOTTI 1962b, 1965), where the number of appendages and their length increases from juveniles to adults. The most diversified chaetotaxy occur in ‘larvae’ of M. granulosus, which have an almost complete set of trunk appendages (B, C, D, E, m1d, m2d, psd and D2) with the result, that this species is characterized by the most pronounced morphological difference between ‘larva’ and adult within the Echiniscidae. The successive (older) instars of M. granulosus are moreover distinguished by a simultaneous and complete reduction of some trunk appendages (m1d, m2d, psd, D2, E) accompanied by an increase in size of lateral projections C and D. The exception to this is M. imberbis, as its ‘larva’ has the same number of projections (appendages) as the adult form. This observation, however, is based on only one specimen (DASTYCH 1999a). Nevertheless, in this species the general trend is expressed in the diminishing size (and change of shape) of some appendages (m2d, psd, E), i.e., from larger in ‘larva’ to gradually smaller in subadults and adults. Four-clawed juveniles (termed here subadults), similar to ‘larvae’ have no genital openings, though a minute (about 1 µm in diameter), pore-like structure has been observed in some older such instars. During successive ecdyses in subadults progressive reduction of appendages occurs, resulting in a species-specific pattern of chaetotaxy. As in ‘larvae’, the number of ecdyses in subadults instars is not known. Subadults have been reported in M. granulosus, M. imberbis, M. frenoti, M. schusteri and M. sp. 1. Marked morphological differences between subadult and adult forms occur in M. schusteri (Figs. 1, 2; see also DASTYCH 1999c). KRISTENSEN (1987) mentioned for Mopsechiniscus that “... At least two juvenile instars exists” and provided some details about chaetotaxy differences between these (subadult) forms.
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In spite of large (and species-specific) morphological differences between juveniles and adults in Mopsechiniscus, individual variability within particular instars in a definite species is relatively small (with some exceptions in M. schusteri) and does not exceed the average variability known from other echiniscid genera. Widely accepted opinion about extreme variability within M. imberbis (RAMAZZOTTI 1972; RAMAZZOTTI & MAUCCI 1983) has prooved to be incorrect, being a result of an artificially expanded variability of this species due to its successive misidentifications. This opinion was even enhanced by the inclusion of morphological characters of juveniles in the diagnosis of adult forms (for details see DASTYCH 1999a).
4. DISTRIBUTION Members of the genus Mopsechiniscus have only been reported from the Southern Hemisphere, where they are widely distributed (Fig. 10). Species are known from South America (M. granulosus, M. schusteri, M. sp. 1, M. sp. 2), mainly in the Andes, from the SubAntarctic in South Georgia (M. imberbis), Crozet Islands (M. frenoti) and from Tasmania (M. tasmanicus). The records of M. schusteri from the Venezuelan Andes (originally identified as M. imberbis by GRIGARICK et al. 1983) represent the northernmost locatities of the genus. KRISTENSEN (1987: p. 294) notes about Mopsechiniscus: “...Perhaps the dispersal of this taxon is limited because it does not tolerate dessication very well. In my moss collection from the Andes the animals were dead after only a few months dessication...”. MIHELCˇ ICˇ (1967) however reported revival of 12% of examined echiniscids (Echiniscus + Mopsechiniscus) after being completely dessicated for 6 years. Recently it also became evident that the species considered by KRISTENSEN (= M. granulosus: comp. DASTYCH & MOSCAL 1992; DASTYCH 1999a) tolerates dessication well, so that the genus has a larger potential dispersal capacity
than was thought. Nevertheless, the taxonomic revision of this species (DASTYCH 2000) indicates that the known distribution pattern of Mopsechiniscus (though only fragmentarily known) is a result of historical factors and subsequent speciation rather than just pure dispersal events. According to available records, therefore M. granulosus seems to be confined to the SSW part of South America. On the other hand, the occurrence of M. frenoti on the remote and geologically relatively young Crozet Islands confirms a potentially vast dispersal capacity for this genus.
5. HABITAT PREFERENCES Biological data on Mopsechiniscus are very limited. Members of the genus have been reported from mosses or lichens, rarely liverworts, in a relatively broad climatic spectrum. In the Sub-Antarctic islands the tardigrades were collected from soil or lithic bryophytes at low or medium altitudes (M. imberbis up to 70 m, M. frenoti: 450–700 m), while in Tierra del Fuego from mosses above the tree line (c. 1000 m a.s.l.: M. sp. 2). Other Mopsechiniscus spp. were recorded mainly from subtropical and/or cloud forests in the Andes at various altitudes (M. granulosus: 50–1100 m, M. schusteri: 1627–2000 m) or at a low altitude in Tasmania (105 m, M. tasmanicus), in bryophytes from different species of Nothofagus or other trees. The association of Mopsechiniscus with bryophytes confined to Nothofagus was noted already by RAMAZZOTTI (1962). M. granulosus is also known from xerophilic bryophytes growing on sun exposed rocks (MIHEL Cˇ I Cˇ 1967). Interestingly, this species was reported by MIHEL CI ˇ Cˇ (l.c.) almost exclusively from lichens occurring, among the other things, in the vicinity of a glacier. KRISTENSEN (1987) was probably referring to M. granulosus, when noting that the “...Nothofagus forests at an altitude 1000–1500 m have the largest population of Mopsechiniscus”, however he provided no more comparative data. Little information is available for M. sp. 1
Fig. 10. Records of Mopsechiniscus spp. (1 – M. schusteri, 2 – M. sp. 1, 3 – M. granulosus, 4 – M. sp. 2, 5 – M. imberbis, 6 – M. frenoti, 7 – M. tasmanicus).
Revisionary notes on Mopsechiniscus (Tardigrada)
from Brazil, the species having been extracted probably from mosses and collected at “Campos de Jordão, ca. de 1900 m” (reported as M. imberbis by DU BOISREYMOND MARCUS 1944). All these data suggest a mountain and/or subpolar character of the genus.
6. PHYLOGENY THULIN (1911) transferred Echiniscus imberbis Richters, 1908, the type species of Mopsechiniscus, to the genus Pseudechiniscus, basing the transfer on the common presence of the pseudosegmental plate. DU BOISREYMOND MARCUS (1944) split the Pseudechiniscuslineage when creating the genus Mopsechiniscus for Richters’ species (in fact, misidentified as another congener). MAUCCI & RAMAZZOTTI (1981) separated from Pseudechiniscus all taxa with dagger-like cirri A and established for them the genus Cornechiniscus. In the classification provided by RAMAZZOTTI & MAUCCI (1983) the Pseudechiniscus-lineage, one of two main phyletic lines recognized within the family Echiniscidae (see THULIN 1928; MARCUS 1929; KRISTENSEN 1987), consists of three stocks represented by the genera Pseudechiniscus, Mopsechiniscus and Cornechiniscus. In the generic revision of the Echiniscidae, KRISTENSEN (1987) separated two other genera (i.e. Proechiniscus and Antechiniscus) from Pseudechiniscus and considered Cornechiniscus a sister group of Mopsechiniscus. The status of Mopsechiniscus within the lineage, as perceived by that author (l.c.), is presented in his Figs. 45–47. There can be little doubt about the monophyly of the clade Pseudechiniscus/Cornechiniscus/Mopsechiniscus, as based on the presence of synapomorphic paired pseudosegmental plates in these taxa. On the other hand, the characters postulated by KRISTENSEN (l.c.) as autapomorphies for the clade Cornechiniscus/Mopsechiniscus and the suggested position of Mopsechiniscus within the Pseudechiniscus-lineage need some comments. The following autapomorphies have been proposed (l.c.) for the clade Cornechiniscus/Mopsechiniscus: “... head segment ventrally bent, mouth opening ventral. Buccal tube long and flexible. Dome shaped secondary clavae ...”. However, since these characters occur partly also in Pseudechiniscus, they cannot be autapomorphies for that suprageneric clade. The location of mouth opening and direction of the head segment is not more ventral in Cornechiniscus/Mopsechiniscus than, for example, in Pseudechiniscus goedeni Grigarick et al., 1964, P. victor (Ehrenberg, 1853), P. occultus Dastych, 1980 or P. alberti Dastych, 1987. A long buccal tube is also not an exclusive feature for the clade, as it occurs within Pseudechiniscus at least in
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P. alberti. In the latter species the buccal apparatus is of the same size as that of M. frenoti, i.e. about 30% of the animal body length. That character should be therefore carefully re-examined in all species of Pseudechiniscus. However, KRISTENSEN (l.c.) gives no information as to how many species of Pseudechiniscus he examined for that feature. The same comments can be made reporting the flexibility of the posterior unit of the buccal tube. Moreover, such a flexibility can be also interpreted as independently acquired in Mopsechiniscus and Cornechiniscus, as that character has already been reported (l.c.) in two other echiniscid genera, i.e. Novechiniscus and Proechiniscus. The dome-shaped secondary clavae (= c2), another autapomorphy postulated for the clade Mopsechiniscus/Cornechiniscus, occur also in Pseudechiniscus, at least in P. alberti, P. occultus and P. bartkei Weglarska, 1962. The branch representing the clade Cornechiniscus/ Mopsechiniscus has been placed by KRISTENSEN closer to the base of cladogram, compared to the branch of the genus Pseudechiniscus (l.c.: Figs. 45–47). Such a position suggests a younger age of origin of the latter taxon compared to the above clade. However, when considering the many evolutionary steps which took place within the clade Mopsechiniscus and, to lesser degree, in Cornechiniscus, compared to the relatively few such changes in Pseudechiniscus, the above postulated placement of the latter genus is questionable. There remains little doubt that the common ancestor of the clade Pseudechiniscus/Cornechiniscus/Mopsechiniscus was more similar to recent species of Pseudechiniscus (at least to those from the P. suillus-group, which may comprise the most ancestral taxa within the genus) than to any member of the other two, more derived genera. Therefore, it is this author’s opinion, that the genus Pseudechiniscus should be placed at the base of that clade and not at its top in that cladogram, where Mopsechiniscus belongs. In spite of the scarcity of information on phyletic relationships within the echiniscids (the knowledge which practically does not exist at the species-level), one can suppose that the members of Mopsechiniscus represent the most derived taxa within the Pseudechiniscus-lineage. That lineage needs a thorough species-level revision based on a clearly defined data matrix and careful polarity assessment of all available characters. Information about diversification within Mopsechiniscus has markedly increased recently and resulting in seven known species, five described and two undescribed (M. sp. 1, 2) (DASTYCH & MOSCAL 1992; DASTYCH 1999a, b, c, 2000). However, these data are still not sufficient for a sound species-level analysis of the phylogenetic relationships. A reliable cladogram cannot be constructed due to large gaps in the morphological data, particularly concerning those of juveniles.
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There are marked differences in the adult chaetotaxy of M. tasmanicus (juveniles not known), compared with the forms from South America, emphasizing that this species is clearly separate from its congeners, the chaetotaxy of the remaining forms being more uniform. The exceptions are, however, the two island species (from South Georgia and Crozet Islands) in which the median plate m2 is provided with short appendages m2d in the species from the first island and very long in that form from the second island group. Furthermore, it appears that the South American taxa, M. granulosus, M. schusteri and M. sp. 1 are more related to each other than to M. sp. 2 from Tierra del Fuego. On the other hand, the latter taxon has the simplest chaetotaxy found within Mopsechiniscus, and may thus resemble the one which occurred in the closest ancestor of this genus. With five of seven known species now reported from South America and adjacent South Georgia, it appears acceptable to assume that the continent was the area of diversification for Mopsechiniscus. Available records, including data from Tasmania, suggest that the genus represents a Gondwanan faunal element (see also DASTYCH & MOSCAL 1992). If this were true, it would also indicate a very ancient origin of these otherwise highly derived echiniscids.
7. COMMENTS RAMAZZOTTI & MAUCCI (1983) and KRISTENSEN (1987) summarized and supplemented information on the genus Mopsechiniscus, recently revised in part by DASTYCH (1999a, b, c, 2000) who added new findings. KRISTENSEN (1987) reported several new autapomorphies in the genus. However, some of his other remarks need additional comments, as they contradict present observations or can be differently interpreted, which is also the case for other echiniscid genera revised by the latter author (l.c.). A review of the interpretation for these other genera is beyond the scope of this paper and will therefore not be dealt with here. KRISTENSEN notes that “... Cornechiniscus has very large, sculptured plates in intersegments 1 and 2, but Mopsechiniscus only in intersegment 1” (l.c., p. 313). However, these structures, i.e. the areas between the dorsal plates on the lateral sides of the body occur in Mopsechiniscus also between segments 3 and 4, i.e., in the KRISTENSEN’s “intersegment 2”. Generally, that low number of intersegment also appears to be incorrect since, when using the nomenclature of KRISTENSEN, the area should be named “intersegment 3”, as the head segment should be included in the count as well. Unclear is the remark “... Cornechiniscus has the fourth pair of legs more or less fused to each other, so they cannot move independently. The same feature is
less well-developed in Mopsechiniscus and Antechiniscus” (l.c., p. 315). The opinion expressed here is that the fourth pair of legs in Mopsechiniscus is no more fused than, for example, in Echiniscus or Pseudechiniscus, so that these legs in Mopsechiniscus can move quite independently. Although the feet of Mopsechiniscus are slightly asymmetrical, the claws of the members of the genus are arranged symmetrically. The remark therefore that “... Mopsechiniscus has slightly asymmetrical claws” (l.c., p. 315) contradicts present observations. The note that “... Dessication-resistant cysts are also found in soil tardigrades of the genera Hypechiniscus, Cornechiniscus, Mopsechiniscus and Pseudechiniscus ...” (l.c., p. 319) is contrary to available data. Though such cysts occur in Mopsechiniscus, none of its congeners has sofar been reported from soil. Males are not rare in Mopsechiniscus as has been suggested (l.c., p. 318). Even in M. granulosus, i.e. in the species on which KRISTENSEN based his generalizing judgement, the sex ratio (females : males) in presently examined material was equal to 14 C :9 F, i.e. almost 40% males, while in M. imberbis and M. frenoti males prevail (10 C :15 F and 1C :2 F, respectively). Also the only known specimen of M. sp. 2 is a male and one of the two known specimens of M. tasmanicus is also a male (the sex of another individual cannot be determined). The only exception is M. schusteri, in which all (14) examined adult specimens were females. Generally, it appears that males in the Echiniscidae occur more often in the Southern than in the Northern Hemisphere (comp. DASTYCH 1987; Claxton 1996; MILLER et al. 1999), the sex ratios presented here confirming that plesiomorphic trait. KRISTENSEN writes “...The existence of “true” larvae in some of the Echiniscidae like Parechiniscus and Mopsechiniscus could be a plesiomorphic character” (l.c., p. 320). Under the ‘“true” larvae’ in Mopsechiniscus the author appears to mean the composite (diversified) chaetotaxy in 2-clawed juveniles, compared to the simple one in adults. The opinion here is that the character (i.e., this particular ‘larval’ chaetotaxy in this genus) is distinctly apomorphic, and the simple chaetotaxy (i.e. that of ‘arctomys’-type) should be considered as plesiomorphic. Such an “arctomys”-type characterizes Parechiniscus, supposedly the most ancestral form of the Echiniscidae, occurs also in the ancestral Oreella (the Oreellidae) and partly in some other, plesiomorphic echiniscids and some less advanced taxa of Echiniscus or Pseudechiniscus. Consequently, the ‘arctomys’-type of chaetotaxy, when found both in juvenile and adult forms, should in general be considered as plesiomorphic trait. This particular, composite chaetotaxy in ‘larvae’ is known within the Echiniscidae only in the highly derived genus Mopsechiniscus.
Revisionary notes on Mopsechiniscus (Tardigrada)
8. IDENTIFICATION KEY FOR SPECIES OF MOPSECHINISCUS (The keys do not include the undescribed species, M. sp. 1 and M. sp. 2 nor the ‘larvae’ of M. tasmanicus and M. frenoti which are not known). Key to postembryonic stages 1. Forms two-clawed, genital area always smooth (i.e without tiny pore). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . first instar (‘larva’) – Forms with four claws, genital area either smooth or with pore-like structure . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Genital area mostly smooth or with tiny (Ø c. 1.0µm), pore-like structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . subadult – Genital area either with 6-lobed papilla (Ø 12–19 µm: C ) or partly double-walled ring-like/oval structure (Ø 3.5–6 µm: F) . . . . . . . . . . . . . . . . . . . . . . . . . . . adult Key to first instars (‘larvae’) 1. Lateral appendages D long filamentous cirri, dorsal appendages m1d and D2 absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. imberbis (Richters) – Lateral appendages D short spines, dorsal appendages m1d and D2 present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granulosus Mihelˇci cˇ Key to subadults 1. Dorsal appendages m1d and m2d absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. schusteri Dastych – Appendages m1d and/or m2d present . . . . . . . . . . . 2 2. Lateral appendages D long, filamentous cirri, at least as long as the maximal body width, dorsal appendages D2 absent . . . . . . . . . M. imberbis (Richters) – Lateral appendages D long spines or short cirri, never longer than the maximal body width, dorsal appendages D2 present . . . . . M. granulosus Mihelˇci cˇ Key to adults 1. Lateral appendages E at least as long as the body . . . . . . . . . . . . . . . . . . . . . M. tasmanicus Dastych & Moscal – Appendages E very short (not longer than 10 µm) or absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Dorsal appendages m2d long filamentous cirri at least 80 µm, i.e., nearly twice as long as the shoulder plate . . . . . . . . . . . . . . . . . . . . . . . . . M. frenoti Dastych – Appendages m2d short spines (≤15 µm) or absent . . 3 3. Appendages m2d short spines. Lateral appendages C and D strongly differentiated in length: C a short tooth, D long, filamentous cirri; the former c. 3–5% of length of D . . . . . . . . . . . . . . . . M. imberbis (Richters)
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– No appendages m2d. Lateral appendages C and D of almost same length or D being mostly slightly longer; C at least 50% of the length of D . . . . . . . . . . . . . . . . 4 4. Appendages A long (sp index 1.9–2.6), C and D long spines or short cirri, both of the same length or D slightly longer cirri; platelet 1 trapezium-like, often with short lateral projection B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granulosus Mihelˇci cˇ – Appendages A short (sp index 0.9–1.4), C and D short wide teeth or short thin spines, mostly of the same length; platelet 1 polygon-like, lateral projection B always absent . . . . . . . . . . . . . . M. schusteri Dastych
Acknowledgements. I wish to thank all persons who kindly loaned specimens of Mopsechiniscus from their collection or otherwise contributed to the access to such material (see also Dastych 1999a-c, 2000): Dr. M. C. Claps (La Plata), Dr. Y. Frenot (Paimpont), Dr. M. Hamer (Pietermaritzburg), Dr. S. L. Heydon (Davis), Dr. R. D. Kathman (Thompson St.), Prof. Dr. R. M. Kristensen (Copenhagen), Mrs Ch. Maucci (Verona), S. L. McInnes B. Sc. (Hons), M. Phil. (Cambridge), T. Meier M. Sc. (Oslo), Prof. Dr. G. C. Rossi (La Plata), Dr. A. Ruiters and Dr. B. R. Stuckenberg (both Pietermaritzburg). I am very grateful to Dr. D. L. Bürkel (Hamburg) for linguistic improvements to the English manuscript and two anonymous referees for their valuable suggestions.
REFERENCES DU BOIS-REYMOND MARCUS, E. (1944): Sobre Tardigrados Brasilieros. Com. Zool. Mus. Hist. Nat. Montevideo 1 (13): 1–19. CLAXTON, S. (1996): Sexual dimorphism in Australian Echiniscus (Tardigrada, Echiniscidae) with descriptions of three new species. Zool. J. Linn. Soc. 116: 13–33. DASTYCH, H. (1987): Two new species of Tardigrada from the Canadian Subarctic with some notes on sexual dimorphism in the family Echiniscidae. Entomol. Mitt. zool. Mus. Hamburg 8 (129): 319–334. DASTYCH, H. (1999a): Redescription of the Sub-Antarctic tardigrade Mopsechiniscus imberbis (Richters, 1908) (Tardigrada). Mitt. hamb. zool. Mus. Inst. 96: 21–35. DASTYCH, H. (1999b): Mopsechiniscus frenoti sp. n., a new water-bear (Tardigrada) from Îles Crozet, the Sub-Antarctic. Entomol. Mitt. zool. Mus. Hamburg 13: 49–57. DASTYCH, H. (1999c): A new species of the genus Mopsechiniscus Du Bois-Reymond Marcus, 1944 (Tardigrada) from the Venezuelan Andes. Acta Biol. Benrodis 10: 91–101. DASTYCH, H. (2000): Redescription of the Neotropical tardigrade Mopsechiniscus granulosus Mihelˇci cˇ , 1967 (Tardigrada). Mitt. hamb. zool. Mus. Inst. 97: 45–57. DASTYCH, H. & MOSCAL, A. M. (1992): Mopsechiniscus tasmanicus sp. n., a new semiterrestrial tardigrade. Entomol. Mitt. zool. Mus. Hamburg 10 (146): 221–228.
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GRIGARICK, A. A., SCHUSTER, R. O. & NELSON, D. R. (1983): Heterotardigrada of Venezuela (Tardigrada). Pan-Pacific Entomol. 59 (1–4): 64–88. KRISTENSEN, R. M. (1987): Generic revision of the Echiniscidae (Heterotardigrada), with a discussion on the origin of the family. Pp. 261–335 in BERTOLANI, R. (ed). Biology of Tardigrades. Selected Symposia and Mongraphs U.Z.I. 1, Mucchi, Modena. MARCUS, E. (1929): Tardigrada. Pp. 1–608 in BRONN, H. G. (ed) Klassen und Ordnungen des Tierreichs. 5 (Abt. 4, Buch 3). Akademische Verlagsgesellschaft, Leipzig. MAUCCI, W. & RAMAZZOTTI, G. (1981): Cornechiniscus gen. nov.: nuova posizione sistematica per i cosiddetti “Pseudechiniscus gruppo cornutus”, con descrizione di una nuova specie (Tardigrada, Echiniscidae). Mem. Ist. Ital. Idrobiol. 39: 147–151. MIHEL Cˇ ICˇ , F. (1967): Ein Beitrag zur Kenntnis der Tardigrades Argentiniens. Verh. Zool.-Bot. Ges. Wien 107: 43–56. MILLER, W. R., CLAXTON, S. K. & HEATWOLE, H. F. (1999): Tardigrades of the Australian Antarctic Territories: males in the genus Echiniscus (Tardigrada: Heterotardigrada). Zool. Anz. 238: 303–309. RAMAZZOTTI, G. (1962): Tardigradi del Cile, con descrizione di quattro nuove specie e di una nuova varieta. Atti Soc. Ital. Sci. Nat. Mus. Civ. Stor. Nat. Milano 101: 275–287. RAMAZZOTTI, G. (1972): Il Phylum Tardigrada (seconda edizione aggiornata). Mem. Ist. Ital. Idrobiol. 28: 1–732. RAMAZZOTTI, G. & MAUCCI, W. (1983): Il phylum Tardigrada (III edizione riveduta e aggiornata). Mem. Ist. Ital. Idrobiol. 41: 1–1012.
RICHTERS, F. (1908): Moosbewohner. Wiss. Ergebn. Schwed. Südpolar Exped., Stockholm 6 (2): 1–16. THULIN, G. (1928): Über die Phylogenie und das System der Tardigraden. Hereditas 11: 207–266.
Author’s address: Hieronymus DASTYCH, Zoologisches Institut und Zoologisches Museum der Universität Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany; Tel.: ++49 40 42838 6379, Fax: ++ 49 40 42838 3937, e-mail: [email protected] Received:18. 09. 2000 Reviewed: 07. 06. 2001 Accepted: 16. 07. 2001 Corresponding Editor: Reinhardt Møbjerg KRISTENSEN
A NOTE ADDED IN PROOF With the proof of this paper I received a reprint of publication by A. Jørgensen [“Cladistic analysis of Echiniscidae Thulin, 1928 (Tardigrada: Heterotardigrada: Echiniscoidea)”; in: Steenstrupia 25: 11–23, 2000] unknown to me. Due to time restraints it is not possible to discuss the results of that work right now in detail but such a discussion will be provided in one of my oncoming papers.
Notes on the Revision of the Genus Mopsechiniscus (Tardigrada)* Hieronymus DASTYCH Zoologisches Institut und Zoologisches Museum der Universität Hamburg, Hamburg, Germany Abstract. A redescription of the semi-terrestrial tardigrade genus Mopsechiniscus from the Southern Hemisphere and identification keys for its members, including instars, are provided. Revised notes on biology, distribution, and phylogeny of the genus are presented. Key words. Tardigrada, Mopsechiniscus redescription.
1. INTRODUCTION While working on tardigrades from the Crozet Islands, several specimens belonging to the rarely reported genus Mopsechiniscus Du Bois-Reymond Marcus, of the ancient semi-terrestrial family Echiniscídae were found. During identification of this material, which turned out to represent a new species (DASTYCH 1999b), it was noticed that there was considerable taxonomic confusion surrounding Mopsechiniscus, in so far as the interpretation of some morphological characters of M. imberbis (Richters, 1908), the type species of the genus, is concerned. It became evident that almost all workers, who had dealt with this genus, including its author, misidentified M. imberbis for various congeners, thus significantly contributing to the confusion (see DASTYCH 1999a for details). To clarify this and other taxonomic questions, a redescription of M. imberbis and M. granulosus MIHEL CI ˇ Cˇ , 1967, which also represents another most often misidentified congener, was provided by DASTYCH (1999a, 2000). Furthermore, a re-examination of specimens from Venezuela reported by GRIGARICK et al. 1983, which allegedly represent the northernmost occurrence of M. imberbis, brought to light another wrong identification, as this material belonged to an undescribed species (DASTYCH 1999c).
*
Contribution to the 8th International Symposium on Tardigrada, Copenhagen, Denmark, 30 July–5 August 2000.
This paper summarizes and discusses new and verified data on morphology of particular members of Mopsechiniscus and their variability, and includes information on distribution, biology and phylogeny of the genus, updates its description and provides identification keys for adults and all known instars. The taxonomic history of Mopsechiniscus is not dealt with as it has been presented elsewhere (DASTYCH 1999a).
2. MATERIAL AND METHODS The paper is based on Mopsechiniscus material from Venezuela, Argentina, Chile, Sub-Antarctic South Georgia, Crozet Islands and Tasmania, including an unidentified individual of Mopsechiniscus from Tierra del Fuego (for the latter see DASTYCH 1999c). Recently some aspects of that material have been presented in a number of papers which are mostly of a revisory character (DASTYCH 1999a, b, c, 2000). The examined specimens are deposited in the Zoologisches Museum Hamburg, British Antarctic Survey (Cambridge), R. M. Bohart Museum (Davis, California), Zoologisk Museum (Copenhagen), Universidad Nacional y Museo (La Plata), Museo Civico de Storia Naturale (Verona), Natal Museum (Pietermaritzburg), and in the private collection of Mr. T. Meier (Oslo). All material is mounted on microscope slides in polyvinyl-lactophenol, Hoyer’s or Faure’s medium and was examined in phase and interference contrast. Photomicrographs were taken with a ZEISS “Axiomat” and “Fotomikroskop III”. Cuticular body projections, depending on their length and shape are alternately being named as cirri, appendages, spines or teeth. The “sp index” (= shoulder plate’ index) expresses the ratio between the length of the considered structure and the length of shoulder plate (see DASTYCH 1999c). 0044-5231/01/240/03–04-299 $ 15.00/0
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List of abbreviations A B bc bp C cs c1 c2 D D2 e ec ex fd i in ic mc m2 m1d m2d n np pl 1 ps psd s sp su tp I, II
– lateral appendage (cirrus) A – lateral appendage B on platelet 1 (at the shoulder plate) – claw basal cusp – leg basal plate – lateral appendage (spine) C at/on platelet 2 (paired plates I) – claw spur – primary clava (= clava) – secondary clava (= cephalic papilla) – lateral appendage (cirrus) D at/on platelet 3 (paired plates II) – dorsal appendage on paired plate II – eye spot – external cusion on leg – external claw – lateral folds on median plate 2 – triangular insertion of the paired plate II – internal claw – internal cushion on leg – mouth cone – median plate 2 – dorsal prtojection on median plate 1 – dorsal projections on median plate 2 – notch – neck plate – platelet 1 – pseudosegmental plate – projections on pseudosegmental plate – leg spur – shoulder plate – subcephalic median plate – terminal plate – the first and the second paired plate.
3. RESULTS Family: Echiniscidae Thulin, 1928 Mopsechiniscus Du Bois-Reymond Marcus Mopsechiniscus Du Bois-Reymond Marcus, 1944: 6 Diagnosis: Echiniscidae with paired pseudosegmental plate. Head without external and internal sensory cirri; prominent dome-shaped cephalic papillae (= secondary clavae). Posterior margin of median plate m2 with a fold. Cirrophore and flagellum of cirrus A fused, without discernible border. Feet slightly asymmetrical due to presence of differently sized cusp- and cushionlike structures on lateral sides of the proximal part of each leg. Two-clawed instars with the same or greater number of trunk appendages compared to adults. Type species: Echiniscus imberbis Richters, 1908, by original designation. Note: The original description of the genus and its redescription (DU BOIS-REYMOND MARCUS 1944; KRI-
1987) are in fact based on an undescribed species of Mopsechiniscus from Brasil and M. granulosus from Argentina. These taxa were at that time misidentified as M. imberbis, the type species (see DASTYCH 1999a for details). Type locality: Sub-Antarctic South Georgia. Other species: M. granulosus Mihelˇciˇc, 1967, M. tasmanicus Dastych & Moscal, 1992, M. frenoti Dastych, 1999, M. schusteri Dastych, 1999, as well as two undescribed species, one of which was reported by DU BOIS-REYMOND MARCUS (1944) from Brazil under the name M. imberbis (here referred to as Mopsechiniscus sp. 1) and the other one from Tierra del Fuego (comp. DASTYCH 1999c), referred to as M. sp. 2. Etymology: Originally not explained. The German prefix “Mops” (= pug or pug-faced) in the generic name may refer to the peculiar appearance of the animal head (see Fig. 7), resulting from the presence of distinct head papillae, and the lack of both pairs of sensory cirri. STENSEN
Amended description Adults Body yellow-reddish to dark-red, dark-brown eye-dots present, not discernible in Mopsechiniscus sp. 2 (see DASTYCH 1999c). Dorsal plates well formed; plates and lateral area between them with a sculptured (‘granulated’) cuticle (Figs. 1, 2). Only M. imberbis with small male genital plates; no other ventral trunk plates present. Head plate with a facet formed by two oval, slightly depressed and closely placed cephalic shields. Facet nearly always well developed in M. imberbis and M. tasmanicus, forming within its posterior part a kind of W-like pattern, but is poorly marked (Figs. 1, 4) or not at all in other congeners. Subcephalic plate usually indistinctly defined, often limited only by two lateral, short and poorly marked cuticular thickenings. Plate, mostly covered with minute, closely placed punctation, has the shape of a weakly marked, median and inverted triangle-like (M. imberbis: Fig. 7: su, M. granulosus) or is a poorly discernible, more square-like structure (M. frenoti). This plate may also be represented by a pair of indistinct oval shields (M. tasmanicus) or can be absent. Neck plate (np) markedly long and distinct, shoulder plate (sp) and paired trunk plates I and II of similar length, pseudosegmental plate (Fig. 1: ps) about onethird shorter than the plates II, terminal plate (tp) median sized, mostly with a pair of long, more or less distinctly marked notches (= incisions; Fig. 1: n). M. imberbis has a sp plate with a more or less distinct, vertically directed keel. In M. granulosus the middle part of the posterior edge of tp plate is often almost parallel to the anterior edge or may even curve towards it.
Revisionary notes on Mopsechiniscus (Tardigrada)
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Figs. 1–3. Mopsechiniscus schusteri Dastych, 1– female, 2 – subadult; Mopsechiniscus frenoti Dastych, 3 – male (All in dorso-lateral view. Figs. 1, 3: holotype, Fig. 2: paratype. Scale bar: 30 µm. Abbreviations explained in text).
Three median plates (m1–3) present, first and third whole, second divided into three-pieces (Figs. 1–4). Plate m1 large and triangular, its apex directed posteriorly and often broadly rounded (M. schusteri: Figs. 1, 2). Plate m2 trapezoidal in its larger anterior part, which is characteristically folded over anterior margin of paired plates II. Second piece of plate m2 shaped like a narrow transverse belt is tucked under the fold and the belt bordering with a small, triangular insertion in the anterior margin of paired plate II. The insertion, a part of the trunk segment III, represents the most posterior part of the plate m2, i.e. its third piece. Lateral edges of plate m2 mostly with two small, usually indistinctly formed but characteristic folds (Figs. 1, 2, 4, 5). Plate m3 the smallest, triangular or rhomboidal in shape (Figs. 1, 5). Each side of dorsal trunk plate with a small, closely placed lateral plate (platelets I–IV), separated from main plate nearly always by a distinct cuticular fold (Figs. 1, 2). A similar fold also limits each platelet posteriorly (Fig. 2: asterisk) and separates it from the closely located base of the leg. Platelet I mostly trapezium-like or in the shape of an irregular polygon (M. schusteri: Figs. 1, 2), platelet apex roundish and
blunt (M. frenoti, M. tasmanicus, some M. granulosus) or terminated in a short distinct tooth (= projection B: in M. imberbis, some M. granulosus). Platelets II and III smaller, more elongated, with poorly defined lateral edges. Posterior parts of these platelets associated (terminated) with lateral appendages C and D, which are species-specifically shaped (e.g. Figs. 1–3). Platelet IV, formed as a more or less distinct lateral lobe of plate tp, located between notch and anteriolateral edge of plate (Fig. 2), is not present in M. frenoti. Head segment ventrally with large, wide based mouth cone and a pair of prominent secondary clavae (= cephalic papillae, c2: Figs. 3, 7). These are oval or roundish and slightly flattened dome-shaped, more or less larger in males than in females. Internal and external sensory cirri absent. The above combination of characters gives the head of Mopsechiniscus species an unmistakable appearance (Fig. 7). Chaetotaxy (= the arrangement and shape of the body appendages) in Mopsechiniscus, as in other echiniscids, is species-specific. The shape of lateral and dorsal appendages varies from long filamentous cirri to short wide and blunt projections, including intermediate forms (for specific details see DASTYCH & MOSCAL
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1992; DASTYCH 1999a, b, c, 2000). The presence of appendages on median plates is a unique character for Mopsechiniscus species (m2d in adults of M. imberbis and M. frenoti: e.g. Figs. 3, 5 and, additionally, m1d in juveniles of M. granulosus and two-clawed instars of M. schusteri: for the latter see GRIGARICK et al., 1983, p. 67). The appendages mostly have a wide base, that in M. tasmanicus is distinctly sculptured internally (DASTYCH & MOSCAL 1992), such sculpturing not being known in other echiniscids. Cirri A mostly formed as slightly flexible appendages of length varying from extremely long in M. tasmanicus to strikingly short in M. schusteri (Figs. 1, 2). Their cirrophores completely fused with the flagellum base, i.e. without a marked border between. The base of cirri A posteriorly with a small, mostly distinctly formed protecting
cavity for primary clava (= clava: c1). These clavae are directed backward (comp. also RAMAZZOTTI 1962), more or less conical and slightly incurved (Figs. 1–3). The apex of the clavae is roundish. Dorsal plates and adjacent lateral sides of the body, including area between the plates, sculptured with distinct, small hemispherical tubercles (knobs: Figs. 1–5), ≤ 2.7 µm diameter (on average 1–2 µm). The knobs representing modified subcuticular pillars, protrude slightly above the cuticle surface and are more or less widely spaced and evenly distributed. Between the knobs in M. imberbis (and partly in M. schusteri and M. sp. 2) occur tiny, closely spaced and barely visible punctation. In M. frenoti these knobs are relatively closely placed, uniformly distributed and arranged almost hexagonally (Fig. 3), being sometimes connected through thin, hard-
Figs. 4–9. Mopsechiniscus granulosus Mihelciˇ ˇ c, 4 – female, dorsal view; Mopsechiniscus imberbis (Richters), 5 – dorsal plates, 6 – external side od leg II, 7 – body anterior, ventral view (male), 8 – internal side of leg I, 9 – claws of leg IV (Fig. 4: specimen from the Villarica Volcano, Chile, Figs. 5–9: vicinity of Husvik, South Georgia. Scale bar for Fig. 4: 20 µm, Fig. 5: 30 µm, Figs. 6–9: 10 µm).
Revisionary notes on Mopsechiniscus (Tardigrada)
ly visible stripes, similar to those occurring in, e.g. Cornechiniscus cornutus (Richters, 1907). In other Mopsechiniscus spp., particularly M. tasmanicus, the knobs are more sparsely and irregularly spaced. Legs median sized, being longest in M. imberbis and shortest in M. schusteri. Sensory spine on leg I absent, sensory papilla on leg IV present. Legs IV without a fringe of spines. Externally, a strongly sclerotized and elongated basal plate (bp: Fig. 2) below the segmental platelet on the proximal part of each leg, i.e. at leg’s base. This plate distinct on legs I–III, but poorly formed on legs IV. Beneath the basal plate an oval or roundish granulated area. Each foot, i.e. the distal part of a leg, is slightly asymmetric due to presence of two cushion- and cusp-like structures of different size, located on each side of claw row, with internal structure (ic: Fig. 8) slightly larger than external one (ec: Fig. 6). Cushions ec are particularly well formed and largest in M. imberbis. Usually, both external and internal cushions have a dorsal keel, being particularly distinct and usually sharply terminated on ec cushion (Fig. 6). This cushion is cusp- or spur-like; ic is longer and more bar-like. The structures are well developed in M. imberbis, distinct in M. granulosus, but are poorly formed in M. frenoti and M. schusteri. In addition, a cuticular spur occurs between granulated area of the legs and the external cushion (ec). The presence and shape of this structure varies in particular species. In M. imberbis the spur is a distinctly conical, wide based and sharply tipped structure (Fig. 6: s), directed posteriorly which increases in size from I to III leg. On legs IV, however, that spur is only a median sized papilla. In other taxa the spur is smaller, shaped as a round-tipped conical structure or poorly defined papilla and is present on legs III and (mostly) also on legs II. Some specimens of M. schusteri have a trace of the spur also on leg I. In M. tasmanicus, due to the unfavourable positioning of the only two known, slidemounted specimens, such a spur could not be seen. Claws are slender and long (M. imberbis: Figs. 6, 8, 9, partly M. frenoti), shorter and less slender (M. tasmanicus, M. schusteri) or intermediate (M. granulosus). The claws increase slightly in length from leg I to IV, those on leg IV are distinctly (20–30%) longer. External claws (ex) slightly shorter than internal (in) and with an elongated base formed by a well defined basal cusp (bc). Internal claws with poorly formed basal cusp occur in M. tasmanicus and M. frenoti; in other species this cusp is more distinct. External claws smooth, internal ones with a well-defined but moderately sized spur (Fig. 9: cs) placed slightly above the claw base, the spur directed towards the claw base. The space between spur and basal cusp is more oval or even sharp-angled on legs I–III, but more roundish on claw IV (Fig. 9), while in M. tasmanicus it is very small and sharp-angled.
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Juveniles Two-clawed juveniles (‘larvae’) which have been found for four species, i.e. M. sp. 1, M. granulosus, M. schusteri and M. imberbis (DU BOIS-REYMOND MARCUS 1944; RAMAZZOTTI 1962; GRIGARICK et al. 1983; DASTYCH 1999a, respectively), have been mostly recorded under the name of M. imberbis. The morphology of these instars is best, though still incompletely, known in M. granulatus, less well in M. imberbis and only fragmentarily in the two remaining taxa (comp. DASTYCH 1999a, 2000). The ‘larvae’ in Mopsechiniscus are characterized by the most diversified chaetotaxy among all the postembrional stages, i.e. they have the largest number of lateral and dorsal appendages compared to adults. This phenomenon is unique for Mopsechiniscus and is contrary to the trend observed in many other Echiniscidae (RAMAZZOTTI 1962b, 1965), where the number of appendages and their length increases from juveniles to adults. The most diversified chaetotaxy occur in ‘larvae’ of M. granulosus, which have an almost complete set of trunk appendages (B, C, D, E, m1d, m2d, psd and D2) with the result, that this species is characterized by the most pronounced morphological difference between ‘larva’ and adult within the Echiniscidae. The successive (older) instars of M. granulosus are moreover distinguished by a simultaneous and complete reduction of some trunk appendages (m1d, m2d, psd, D2, E) accompanied by an increase in size of lateral projections C and D. The exception to this is M. imberbis, as its ‘larva’ has the same number of projections (appendages) as the adult form. This observation, however, is based on only one specimen (DASTYCH 1999a). Nevertheless, in this species the general trend is expressed in the diminishing size (and change of shape) of some appendages (m2d, psd, E), i.e., from larger in ‘larva’ to gradually smaller in subadults and adults. Four-clawed juveniles (termed here subadults), similar to ‘larvae’ have no genital openings, though a minute (about 1 µm in diameter), pore-like structure has been observed in some older such instars. During successive ecdyses in subadults progressive reduction of appendages occurs, resulting in a species-specific pattern of chaetotaxy. As in ‘larvae’, the number of ecdyses in subadults instars is not known. Subadults have been reported in M. granulosus, M. imberbis, M. frenoti, M. schusteri and M. sp. 1. Marked morphological differences between subadult and adult forms occur in M. schusteri (Figs. 1, 2; see also DASTYCH 1999c). KRISTENSEN (1987) mentioned for Mopsechiniscus that “... At least two juvenile instars exists” and provided some details about chaetotaxy differences between these (subadult) forms.
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In spite of large (and species-specific) morphological differences between juveniles and adults in Mopsechiniscus, individual variability within particular instars in a definite species is relatively small (with some exceptions in M. schusteri) and does not exceed the average variability known from other echiniscid genera. Widely accepted opinion about extreme variability within M. imberbis (RAMAZZOTTI 1972; RAMAZZOTTI & MAUCCI 1983) has prooved to be incorrect, being a result of an artificially expanded variability of this species due to its successive misidentifications. This opinion was even enhanced by the inclusion of morphological characters of juveniles in the diagnosis of adult forms (for details see DASTYCH 1999a).
4. DISTRIBUTION Members of the genus Mopsechiniscus have only been reported from the Southern Hemisphere, where they are widely distributed (Fig. 10). Species are known from South America (M. granulosus, M. schusteri, M. sp. 1, M. sp. 2), mainly in the Andes, from the SubAntarctic in South Georgia (M. imberbis), Crozet Islands (M. frenoti) and from Tasmania (M. tasmanicus). The records of M. schusteri from the Venezuelan Andes (originally identified as M. imberbis by GRIGARICK et al. 1983) represent the northernmost locatities of the genus. KRISTENSEN (1987: p. 294) notes about Mopsechiniscus: “...Perhaps the dispersal of this taxon is limited because it does not tolerate dessication very well. In my moss collection from the Andes the animals were dead after only a few months dessication...”. MIHELCˇ ICˇ (1967) however reported revival of 12% of examined echiniscids (Echiniscus + Mopsechiniscus) after being completely dessicated for 6 years. Recently it also became evident that the species considered by KRISTENSEN (= M. granulosus: comp. DASTYCH & MOSCAL 1992; DASTYCH 1999a) tolerates dessication well, so that the genus has a larger potential dispersal capacity
than was thought. Nevertheless, the taxonomic revision of this species (DASTYCH 2000) indicates that the known distribution pattern of Mopsechiniscus (though only fragmentarily known) is a result of historical factors and subsequent speciation rather than just pure dispersal events. According to available records, therefore M. granulosus seems to be confined to the SSW part of South America. On the other hand, the occurrence of M. frenoti on the remote and geologically relatively young Crozet Islands confirms a potentially vast dispersal capacity for this genus.
5. HABITAT PREFERENCES Biological data on Mopsechiniscus are very limited. Members of the genus have been reported from mosses or lichens, rarely liverworts, in a relatively broad climatic spectrum. In the Sub-Antarctic islands the tardigrades were collected from soil or lithic bryophytes at low or medium altitudes (M. imberbis up to 70 m, M. frenoti: 450–700 m), while in Tierra del Fuego from mosses above the tree line (c. 1000 m a.s.l.: M. sp. 2). Other Mopsechiniscus spp. were recorded mainly from subtropical and/or cloud forests in the Andes at various altitudes (M. granulosus: 50–1100 m, M. schusteri: 1627–2000 m) or at a low altitude in Tasmania (105 m, M. tasmanicus), in bryophytes from different species of Nothofagus or other trees. The association of Mopsechiniscus with bryophytes confined to Nothofagus was noted already by RAMAZZOTTI (1962). M. granulosus is also known from xerophilic bryophytes growing on sun exposed rocks (MIHEL Cˇ I Cˇ 1967). Interestingly, this species was reported by MIHEL CI ˇ Cˇ (l.c.) almost exclusively from lichens occurring, among the other things, in the vicinity of a glacier. KRISTENSEN (1987) was probably referring to M. granulosus, when noting that the “...Nothofagus forests at an altitude 1000–1500 m have the largest population of Mopsechiniscus”, however he provided no more comparative data. Little information is available for M. sp. 1
Fig. 10. Records of Mopsechiniscus spp. (1 – M. schusteri, 2 – M. sp. 1, 3 – M. granulosus, 4 – M. sp. 2, 5 – M. imberbis, 6 – M. frenoti, 7 – M. tasmanicus).
Revisionary notes on Mopsechiniscus (Tardigrada)
from Brazil, the species having been extracted probably from mosses and collected at “Campos de Jordão, ca. de 1900 m” (reported as M. imberbis by DU BOISREYMOND MARCUS 1944). All these data suggest a mountain and/or subpolar character of the genus.
6. PHYLOGENY THULIN (1911) transferred Echiniscus imberbis Richters, 1908, the type species of Mopsechiniscus, to the genus Pseudechiniscus, basing the transfer on the common presence of the pseudosegmental plate. DU BOISREYMOND MARCUS (1944) split the Pseudechiniscuslineage when creating the genus Mopsechiniscus for Richters’ species (in fact, misidentified as another congener). MAUCCI & RAMAZZOTTI (1981) separated from Pseudechiniscus all taxa with dagger-like cirri A and established for them the genus Cornechiniscus. In the classification provided by RAMAZZOTTI & MAUCCI (1983) the Pseudechiniscus-lineage, one of two main phyletic lines recognized within the family Echiniscidae (see THULIN 1928; MARCUS 1929; KRISTENSEN 1987), consists of three stocks represented by the genera Pseudechiniscus, Mopsechiniscus and Cornechiniscus. In the generic revision of the Echiniscidae, KRISTENSEN (1987) separated two other genera (i.e. Proechiniscus and Antechiniscus) from Pseudechiniscus and considered Cornechiniscus a sister group of Mopsechiniscus. The status of Mopsechiniscus within the lineage, as perceived by that author (l.c.), is presented in his Figs. 45–47. There can be little doubt about the monophyly of the clade Pseudechiniscus/Cornechiniscus/Mopsechiniscus, as based on the presence of synapomorphic paired pseudosegmental plates in these taxa. On the other hand, the characters postulated by KRISTENSEN (l.c.) as autapomorphies for the clade Cornechiniscus/Mopsechiniscus and the suggested position of Mopsechiniscus within the Pseudechiniscus-lineage need some comments. The following autapomorphies have been proposed (l.c.) for the clade Cornechiniscus/Mopsechiniscus: “... head segment ventrally bent, mouth opening ventral. Buccal tube long and flexible. Dome shaped secondary clavae ...”. However, since these characters occur partly also in Pseudechiniscus, they cannot be autapomorphies for that suprageneric clade. The location of mouth opening and direction of the head segment is not more ventral in Cornechiniscus/Mopsechiniscus than, for example, in Pseudechiniscus goedeni Grigarick et al., 1964, P. victor (Ehrenberg, 1853), P. occultus Dastych, 1980 or P. alberti Dastych, 1987. A long buccal tube is also not an exclusive feature for the clade, as it occurs within Pseudechiniscus at least in
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P. alberti. In the latter species the buccal apparatus is of the same size as that of M. frenoti, i.e. about 30% of the animal body length. That character should be therefore carefully re-examined in all species of Pseudechiniscus. However, KRISTENSEN (l.c.) gives no information as to how many species of Pseudechiniscus he examined for that feature. The same comments can be made reporting the flexibility of the posterior unit of the buccal tube. Moreover, such a flexibility can be also interpreted as independently acquired in Mopsechiniscus and Cornechiniscus, as that character has already been reported (l.c.) in two other echiniscid genera, i.e. Novechiniscus and Proechiniscus. The dome-shaped secondary clavae (= c2), another autapomorphy postulated for the clade Mopsechiniscus/Cornechiniscus, occur also in Pseudechiniscus, at least in P. alberti, P. occultus and P. bartkei Weglarska, 1962. The branch representing the clade Cornechiniscus/ Mopsechiniscus has been placed by KRISTENSEN closer to the base of cladogram, compared to the branch of the genus Pseudechiniscus (l.c.: Figs. 45–47). Such a position suggests a younger age of origin of the latter taxon compared to the above clade. However, when considering the many evolutionary steps which took place within the clade Mopsechiniscus and, to lesser degree, in Cornechiniscus, compared to the relatively few such changes in Pseudechiniscus, the above postulated placement of the latter genus is questionable. There remains little doubt that the common ancestor of the clade Pseudechiniscus/Cornechiniscus/Mopsechiniscus was more similar to recent species of Pseudechiniscus (at least to those from the P. suillus-group, which may comprise the most ancestral taxa within the genus) than to any member of the other two, more derived genera. Therefore, it is this author’s opinion, that the genus Pseudechiniscus should be placed at the base of that clade and not at its top in that cladogram, where Mopsechiniscus belongs. In spite of the scarcity of information on phyletic relationships within the echiniscids (the knowledge which practically does not exist at the species-level), one can suppose that the members of Mopsechiniscus represent the most derived taxa within the Pseudechiniscus-lineage. That lineage needs a thorough species-level revision based on a clearly defined data matrix and careful polarity assessment of all available characters. Information about diversification within Mopsechiniscus has markedly increased recently and resulting in seven known species, five described and two undescribed (M. sp. 1, 2) (DASTYCH & MOSCAL 1992; DASTYCH 1999a, b, c, 2000). However, these data are still not sufficient for a sound species-level analysis of the phylogenetic relationships. A reliable cladogram cannot be constructed due to large gaps in the morphological data, particularly concerning those of juveniles.
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There are marked differences in the adult chaetotaxy of M. tasmanicus (juveniles not known), compared with the forms from South America, emphasizing that this species is clearly separate from its congeners, the chaetotaxy of the remaining forms being more uniform. The exceptions are, however, the two island species (from South Georgia and Crozet Islands) in which the median plate m2 is provided with short appendages m2d in the species from the first island and very long in that form from the second island group. Furthermore, it appears that the South American taxa, M. granulosus, M. schusteri and M. sp. 1 are more related to each other than to M. sp. 2 from Tierra del Fuego. On the other hand, the latter taxon has the simplest chaetotaxy found within Mopsechiniscus, and may thus resemble the one which occurred in the closest ancestor of this genus. With five of seven known species now reported from South America and adjacent South Georgia, it appears acceptable to assume that the continent was the area of diversification for Mopsechiniscus. Available records, including data from Tasmania, suggest that the genus represents a Gondwanan faunal element (see also DASTYCH & MOSCAL 1992). If this were true, it would also indicate a very ancient origin of these otherwise highly derived echiniscids.
7. COMMENTS RAMAZZOTTI & MAUCCI (1983) and KRISTENSEN (1987) summarized and supplemented information on the genus Mopsechiniscus, recently revised in part by DASTYCH (1999a, b, c, 2000) who added new findings. KRISTENSEN (1987) reported several new autapomorphies in the genus. However, some of his other remarks need additional comments, as they contradict present observations or can be differently interpreted, which is also the case for other echiniscid genera revised by the latter author (l.c.). A review of the interpretation for these other genera is beyond the scope of this paper and will therefore not be dealt with here. KRISTENSEN notes that “... Cornechiniscus has very large, sculptured plates in intersegments 1 and 2, but Mopsechiniscus only in intersegment 1” (l.c., p. 313). However, these structures, i.e. the areas between the dorsal plates on the lateral sides of the body occur in Mopsechiniscus also between segments 3 and 4, i.e., in the KRISTENSEN’s “intersegment 2”. Generally, that low number of intersegment also appears to be incorrect since, when using the nomenclature of KRISTENSEN, the area should be named “intersegment 3”, as the head segment should be included in the count as well. Unclear is the remark “... Cornechiniscus has the fourth pair of legs more or less fused to each other, so they cannot move independently. The same feature is
less well-developed in Mopsechiniscus and Antechiniscus” (l.c., p. 315). The opinion expressed here is that the fourth pair of legs in Mopsechiniscus is no more fused than, for example, in Echiniscus or Pseudechiniscus, so that these legs in Mopsechiniscus can move quite independently. Although the feet of Mopsechiniscus are slightly asymmetrical, the claws of the members of the genus are arranged symmetrically. The remark therefore that “... Mopsechiniscus has slightly asymmetrical claws” (l.c., p. 315) contradicts present observations. The note that “... Dessication-resistant cysts are also found in soil tardigrades of the genera Hypechiniscus, Cornechiniscus, Mopsechiniscus and Pseudechiniscus ...” (l.c., p. 319) is contrary to available data. Though such cysts occur in Mopsechiniscus, none of its congeners has sofar been reported from soil. Males are not rare in Mopsechiniscus as has been suggested (l.c., p. 318). Even in M. granulosus, i.e. in the species on which KRISTENSEN based his generalizing judgement, the sex ratio (females : males) in presently examined material was equal to 14 C :9 F, i.e. almost 40% males, while in M. imberbis and M. frenoti males prevail (10 C :15 F and 1C :2 F, respectively). Also the only known specimen of M. sp. 2 is a male and one of the two known specimens of M. tasmanicus is also a male (the sex of another individual cannot be determined). The only exception is M. schusteri, in which all (14) examined adult specimens were females. Generally, it appears that males in the Echiniscidae occur more often in the Southern than in the Northern Hemisphere (comp. DASTYCH 1987; Claxton 1996; MILLER et al. 1999), the sex ratios presented here confirming that plesiomorphic trait. KRISTENSEN writes “...The existence of “true” larvae in some of the Echiniscidae like Parechiniscus and Mopsechiniscus could be a plesiomorphic character” (l.c., p. 320). Under the ‘“true” larvae’ in Mopsechiniscus the author appears to mean the composite (diversified) chaetotaxy in 2-clawed juveniles, compared to the simple one in adults. The opinion here is that the character (i.e., this particular ‘larval’ chaetotaxy in this genus) is distinctly apomorphic, and the simple chaetotaxy (i.e. that of ‘arctomys’-type) should be considered as plesiomorphic. Such an “arctomys”-type characterizes Parechiniscus, supposedly the most ancestral form of the Echiniscidae, occurs also in the ancestral Oreella (the Oreellidae) and partly in some other, plesiomorphic echiniscids and some less advanced taxa of Echiniscus or Pseudechiniscus. Consequently, the ‘arctomys’-type of chaetotaxy, when found both in juvenile and adult forms, should in general be considered as plesiomorphic trait. This particular, composite chaetotaxy in ‘larvae’ is known within the Echiniscidae only in the highly derived genus Mopsechiniscus.
Revisionary notes on Mopsechiniscus (Tardigrada)
8. IDENTIFICATION KEY FOR SPECIES OF MOPSECHINISCUS (The keys do not include the undescribed species, M. sp. 1 and M. sp. 2 nor the ‘larvae’ of M. tasmanicus and M. frenoti which are not known). Key to postembryonic stages 1. Forms two-clawed, genital area always smooth (i.e without tiny pore). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . first instar (‘larva’) – Forms with four claws, genital area either smooth or with pore-like structure . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Genital area mostly smooth or with tiny (Ø c. 1.0µm), pore-like structure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . subadult – Genital area either with 6-lobed papilla (Ø 12–19 µm: C ) or partly double-walled ring-like/oval structure (Ø 3.5–6 µm: F) . . . . . . . . . . . . . . . . . . . . . . . . . . . adult Key to first instars (‘larvae’) 1. Lateral appendages D long filamentous cirri, dorsal appendages m1d and D2 absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. imberbis (Richters) – Lateral appendages D short spines, dorsal appendages m1d and D2 present . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granulosus Mihelˇci cˇ Key to subadults 1. Dorsal appendages m1d and m2d absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. schusteri Dastych – Appendages m1d and/or m2d present . . . . . . . . . . . 2 2. Lateral appendages D long, filamentous cirri, at least as long as the maximal body width, dorsal appendages D2 absent . . . . . . . . . M. imberbis (Richters) – Lateral appendages D long spines or short cirri, never longer than the maximal body width, dorsal appendages D2 present . . . . . M. granulosus Mihelˇci cˇ Key to adults 1. Lateral appendages E at least as long as the body . . . . . . . . . . . . . . . . . . . . . M. tasmanicus Dastych & Moscal – Appendages E very short (not longer than 10 µm) or absent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Dorsal appendages m2d long filamentous cirri at least 80 µm, i.e., nearly twice as long as the shoulder plate . . . . . . . . . . . . . . . . . . . . . . . . . M. frenoti Dastych – Appendages m2d short spines (≤15 µm) or absent . . 3 3. Appendages m2d short spines. Lateral appendages C and D strongly differentiated in length: C a short tooth, D long, filamentous cirri; the former c. 3–5% of length of D . . . . . . . . . . . . . . . . M. imberbis (Richters)
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– No appendages m2d. Lateral appendages C and D of almost same length or D being mostly slightly longer; C at least 50% of the length of D . . . . . . . . . . . . . . . . 4 4. Appendages A long (sp index 1.9–2.6), C and D long spines or short cirri, both of the same length or D slightly longer cirri; platelet 1 trapezium-like, often with short lateral projection B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . M. granulosus Mihelˇci cˇ – Appendages A short (sp index 0.9–1.4), C and D short wide teeth or short thin spines, mostly of the same length; platelet 1 polygon-like, lateral projection B always absent . . . . . . . . . . . . . . M. schusteri Dastych
Acknowledgements. I wish to thank all persons who kindly loaned specimens of Mopsechiniscus from their collection or otherwise contributed to the access to such material (see also Dastych 1999a-c, 2000): Dr. M. C. Claps (La Plata), Dr. Y. Frenot (Paimpont), Dr. M. Hamer (Pietermaritzburg), Dr. S. L. Heydon (Davis), Dr. R. D. Kathman (Thompson St.), Prof. Dr. R. M. Kristensen (Copenhagen), Mrs Ch. Maucci (Verona), S. L. McInnes B. Sc. (Hons), M. Phil. (Cambridge), T. Meier M. Sc. (Oslo), Prof. Dr. G. C. Rossi (La Plata), Dr. A. Ruiters and Dr. B. R. Stuckenberg (both Pietermaritzburg). I am very grateful to Dr. D. L. Bürkel (Hamburg) for linguistic improvements to the English manuscript and two anonymous referees for their valuable suggestions.
REFERENCES DU BOIS-REYMOND MARCUS, E. (1944): Sobre Tardigrados Brasilieros. Com. Zool. Mus. Hist. Nat. Montevideo 1 (13): 1–19. CLAXTON, S. (1996): Sexual dimorphism in Australian Echiniscus (Tardigrada, Echiniscidae) with descriptions of three new species. Zool. J. Linn. Soc. 116: 13–33. DASTYCH, H. (1987): Two new species of Tardigrada from the Canadian Subarctic with some notes on sexual dimorphism in the family Echiniscidae. Entomol. Mitt. zool. Mus. Hamburg 8 (129): 319–334. DASTYCH, H. (1999a): Redescription of the Sub-Antarctic tardigrade Mopsechiniscus imberbis (Richters, 1908) (Tardigrada). Mitt. hamb. zool. Mus. Inst. 96: 21–35. DASTYCH, H. (1999b): Mopsechiniscus frenoti sp. n., a new water-bear (Tardigrada) from Îles Crozet, the Sub-Antarctic. Entomol. Mitt. zool. Mus. Hamburg 13: 49–57. DASTYCH, H. (1999c): A new species of the genus Mopsechiniscus Du Bois-Reymond Marcus, 1944 (Tardigrada) from the Venezuelan Andes. Acta Biol. Benrodis 10: 91–101. DASTYCH, H. (2000): Redescription of the Neotropical tardigrade Mopsechiniscus granulosus Mihelˇci cˇ , 1967 (Tardigrada). Mitt. hamb. zool. Mus. Inst. 97: 45–57. DASTYCH, H. & MOSCAL, A. M. (1992): Mopsechiniscus tasmanicus sp. n., a new semiterrestrial tardigrade. Entomol. Mitt. zool. Mus. Hamburg 10 (146): 221–228.
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Author’s address: Hieronymus DASTYCH, Zoologisches Institut und Zoologisches Museum der Universität Hamburg, Martin-Luther-King-Platz 3, D-20146 Hamburg, Germany; Tel.: ++49 40 42838 6379, Fax: ++ 49 40 42838 3937, e-mail: [email protected] Received:18. 09. 2000 Reviewed: 07. 06. 2001 Accepted: 16. 07. 2001 Corresponding Editor: Reinhardt Møbjerg KRISTENSEN
A NOTE ADDED IN PROOF With the proof of this paper I received a reprint of publication by A. Jørgensen [“Cladistic analysis of Echiniscidae Thulin, 1928 (Tardigrada: Heterotardigrada: Echiniscoidea)”; in: Steenstrupia 25: 11–23, 2000] unknown to me. Due to time restraints it is not possible to discuss the results of that work right now in detail but such a discussion will be provided in one of my oncoming papers.