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Infraciliature and silverline system of the ciliate Pseudotrachelocerca trepida (Kahl, 1928), nov. gen., nov. comb., and establishment of a new family, the pseudotrachelocercidae nov. fam. (Ciliophora, Haptoria)
Europ.J.Protistol. 26, 160-166 (1990) October 19, 1990
Eu ropean Journ al of
PROTISTOLOGY
Infraciliature and Silverline System of the Ciliate Pseudotrachelocerca trepida (Kahl, 1928), nov. gen., nov comb., and Establishment of a New Family, the Pseudotrachelocercidae nov fam. (Ciliophora, Haptoria) Weibo Song College of Fisheries, Ocean University of Qingdao, Qingdao, People's Republic of China
SUMMARY The morphology, infra ciliature and silverline system of Trachelocerca trepida Kahl, 192 8 has been reinvestigated. The species was found in marine water (Yellow Sea) near Shanghai, Eastchina. Sta ined specimens (protargo l) are characterized morphometr ically. The shape of the extrusomes (tox icysts) and the structure of oral as well as somatic kinetids indicate that this species must be sepa rated from the genus Trachelocerca. A new genus, Pseudotrachelocerca, characterized by an extensible neck, spindle-like toxicysts, irregular dorsal brush and widely meshed sliverline system, is thus erected. Based on the parti cular dorsal brush and silverline system the new family Pseudotra chelocercidae, nov. fam. is established. It can be possibly placed in the subclass Haptoria, ord er Spathidiida. However, a definite classification has to await fine structural investigations.
Introduction Mo st of our knowledge of the Kinetofr agminoph or a taxonomy comes from investigations performed with traditional methods and, above all, from the observation of living cells only. This is, however, frequently insufficient to give a clear classification of these extremely diverse carnivores. A still unr esolved question is which characteristics can be used as key for a natural classification. In recent years much weight has been put on the ora l apparatus, nematodesmata and silverline system [4, 5, 18-21, 23, 36, 42J because of the similarity of genera l kinetid structure within the class. Ne w studies strongly support higher categories and more taxa for the Haptoria [34], because all evidence indicates that those "pr imitive" kinetofragminophoran ciliates are much more differentiated than earlier work ers supposed. 093 2-4 73 9/90/002 6-0160 $3.50/0
Material and Methods Small numbe rs of Pseudotrachelocerca trepida were found in a seawa ter sample in Sheya ng County, near Shanghai, Eastchina. Th ey were culture d in a petri dish with wheat grains and distilled sea water (salinity ca. 27%0). Observation on living cells was carried out with a microscope equipped with ph ase-contrast optics. For revealing the infraciliature the protargol silver sta ining method according to Wilbert [43] was used. The silverline system was studied in specimens impregnated by the Chatton-Lwoff silver method as modified by Corliss [11]. All measurements and draw ings were perform ed at a magnification of 1600 x with vario us instrum ents. The termin ology is accord ing to Kahl [35], Corliss [12], Foissner [21] and Berger et al. [4]. The classification is after Small & Lynn [40 ] and Foissner & Foissner [25]. Th e following abbreviations are used in the figures: © 1990 by Gustav Fischer Verlag, Stuttgart
Redescription of Pseudotrachelocerca trepida . 161 ApF BB CoC CoK Cs CV DB Ex FV IkL Ma Nd OB PoK SK TI TMt Tox
= argyrophilic fiber =
=
= = =
= = =
= = = =
= = = =
=
basal body circumoral ciliature circumoral kinety cytostome contractile vacuole dorsal brush extrusome food vacuoles interkinetal silverline macronucleus nematodesmata oral bulge pararal kinetids somatic kinety transverse silverline transverse microtubules toxicysts
Results Subclass Haptoria Corliss, 1974 Order Spathidiida Foissner & Foissner, 1988 Family Pseudotrachelocercidae nov. fam.
Diagnosis. Cylindrical or bottle-shaped Spathidiina with meridional somatic kineties; dorsal brush irregular, consists of densely spaced basal body pairs not arranged in rows and connected posteriorly with only a single kinety; silverline system widely meshed. Type genus: Pseudotrachelocerca nov. gen. According to Foissner & Foissner [25], the diagnosis of the Order Spathidiida Foissner & Foissner, 1988 is "Cytostome apical, round or slit-like, in suborder Didiniina on top of cone-like proboscis; rhabdos made of three microtubular components: transverse ribbons originating from the nonciliated kinetosomes of the oral dikinetids, nematodesmal bundles originating exclusively from the same source, and bulge microtubules; somatic ciliation uniform or limited to dense bands which, however, rest within longitudinally running kineties composed of nonciliated kinetids; dorsal brush composed of 2 to many kineties; toxicysts localized, typically in or near oral area; free-living" . It is not clear yet, whether the situation of the dorsal brush is a "key" character for the order; if so the diagnosis must be changed a little to include taxa having a dorsal brush "connected" with only one somatic kinety, or a new order should probably be erected for the new family. In the suborder Spathidiina four families are placed [25]: Spathidiidae Kahl in Doflein and Reichenow, 1929, Trachelophyllidae Kent, 1882, Lacrymariidae Fromentel, 1876, and Homalozoonidae Jankowski, 1980. The new family studied here differs from the other ones, especially from the Trachelophyllidae, by its band-like condensed monokinetids around the cytostome, the dorsal brush and the widely meshed silverline system.
Genus Pseudotrachelocerca nov. gen.
Diagnosis. Pseudotrachelocercidae with a somewhat extensible neck and short rod- or spindle-like extrusomes (toxicysts) localized typically in or near oral area; cytostome apical, elliptical; nematodes mal bundles originating from oral dikinetids (circumoral kinety); somatic kineties anteriorly with "paroral" monokinetids; dorsal brush and silverline system with characteristics of the family (see above). Type-species: Pseudotrachelocerca trepida (Kahl, 1928) nov. comb. Dragesco [15] investigated a new marine ciliate (Paraspathidium obliquum) and furthermore, erected a new genus, Paraspathidium, due to the existence of "trichites" within the cytopharynx. Its infraciliature was later described by Agamaliev [1]. More or less like Pseudotrachelocerca trepida, it also possesses densely arranged kinetids which are anteriorly around the cytostome and has, as the author pictured, probably two fragments of circumoral kinety (?or anterior ends of toxicysts ?). Unfortunately, the silverline system and dorsal brush of Paraspathidium obliquum remain unknown, and a comparison between Paraspathidium and Pseudotrachelocerca is therefore impossible. Another marine genus, Trachelocerca, as redescribed by Dragesco [13], is equipped with very long, distinct "fibrils" (toxicysts? trichites?) in the oral region, and has many node-like bumps on its bulge. Until now, a detailed morphological investigation of the infraciliature, as far as I know, has not been performed. Hence, the new genus can be merely separated from Trachelocerca morphologically because of the absence of distinctive trichitelike structures in Pseudotrachelocerca.
Pseudotrachelocerca trepida (Kahl, 1928) nov. comb. (Figs. 1-19) Syn. Trachelocerca trepida Kahl, 1928 Enchelyoden trepida (Kahl, 1928) Borror, 1965
New diagnosis. In vivo about 80-160 X 30 urn; neck region somewhat contractile; body bottle-shaped, sometimes slightly flattened dorsoventrally. Macronucleus Uor S-shaped; single contractile vacuole posteriorly; Extrusomes (toxicysts) genus-specific, mostly around the cytostome; 28 meridional somatic kineties on average. Redescription. Body shape in vivo moderately variable, anterior third neck-like narrowed, can be slightly curved in all directions. Anterior end more or less coned but not truncated as depicted by Kahl [35]; posteriorly rounded, sometimes bag-like. Oral opening oval to long elliptic, lies polar on small, indistinct oral bulge (Fig. 10), hardly recognizable in vivo. Nematodesmata not recognizable in vivo. Cilia ca. 5-8!-lm long, which at the oral end (circumoral ciliation) increase to ca. 10 urn and, like that of Phialina, form a tuft with 5 girdles of cilia and beat anteriorly when feeding. Cilia of dorsal brush about 4-5 urn, very difficult to recognize in living cells.
162 . Song
5
"~I
Spm
.:- :
··:·.;":,7:·.~ ~-: .. :...:. "\ " "'. ':. : : : .;::" -
(V
'~<:;~~:." .:~.>_:-
- ( VP
6
Figs. 1- 7. Morphol ogy of Pseudotrachelocerca trepida from life (Figs. 1-4) and from protargol-impregnated specimens (Figs. 5 - 7). Figs. 1-4. Various individuals. - Fig. 5. Extrusomes (toxicysts). - Fig. 6. Ventral view. - Fig. 7. Dorsal view.
~;;:----OB
10pm
10
9
11
Figs. 8- 12. Morphology of Pseudotrachelocerca trepida from protargol-impregn ated specimens (Figs. 8- 11) and after Charron-Lwoff method (Fig. 12). - Fig. 8. Lateral view. - Fig. 9. Dorsal view of the anterior region. - Fig. 10. View of the anterior pole. Fig. 11. Argentoph ilic granules (fiber system?)after protargol-impregnation. - Fig. 12. Part of the silverline system, the arrow points to the interkinetal silverline.
13
Figs. 13-19. M orphology of Pseud otrachelocerca trepida. Light micrographs of Pseudotra chelocerca trepida (a bbrevia tions see th e text). - Fig. 13. Protar gol- impregnated specimen, show ing th e densely grouped paroral ki netids (poK ) around the cytostome. N ote th e heav ily impregnat ed gra nules (chro matin ?) within th e mac ronucleus (M a) . - Figs. 14, 15. Anterior parts of specimens, th e arrow indicates the dorsal brush. - Fig. 16. Extrusornes (Toxicysts), - Fig. 17. Ventral view of a specimen, showing the nernat od esrnal bundles (Nd). - Fig. 18. Infraciliature in anterior reg ion of th e cell (after protargol imp regnat ion ) showing the circumor al kin ety (a rro w ). - Fig. 19. Silverlin e system after Chatton-Lwoff meth od.
164 . Song
Pellicle thin and smooth, not indented by ciliary rows as described by Kahl [35]; beneath pellicle no special granules recognisable. Extrusomes occur both aro und cytostome and within cytoplasm, short rod- or spindle-shaped, often heavily stained with protargol (Figs. 5, 8). Cytoplasm very hyaline, colorless, usually densely filled with numerous dark grey, ca. 2/lm particles (Fig. 1). Macronucleus usually horseshoe-shaped, centrally located, with numerous nucleoli; micronucleus not found, presumably too near to macronucleus. Movement moderately rapid, usually swimming ahead in straigh t line while rotating around longitudinal body axis. Feeds possibly mainly on bacteria both in nature and in culture . Somatic kineties course longitudinally, composed of monokinetids; distance between basal bodies smaller anter iorly th an posteriorly (Figs. 6, 7). After protargol impregnation a fiber running along each kinety is often noticeable (Fig. 11). At base of oral bulge a circumoral kinety composed of dikinetids is present (Figs. 9, 10, 18); the number of the basal body pairs of this kinety is smaller than that of somatic kinetics (Tab. 1). Dikinetids obliquely arranged, the anterior basal body of each bears a nematodesmal bundle ("outer rhabdos" ?). 5 basal bodies distinctly condensed at anterior end of each kinety thus forming a kinetosome band which surrounds the cytostome (POK in Figs. 6, 9, 10, 13). From those condensed kinetids, which run often slightly at an angle to somatic kineties, no nematodesmata originate. After protargol impregnation the rhabdos is composed of, very probably, only one component: the nematodesmal bundles which originate from the anterior kinetosomes of the oral dikinetids (CoK in Figs. 9, 17). Dorsal brush very characteristic: made up of many basal body pairs which arc "piled up" irregularly, unlike those in other haptoridfamilies, where it forms regular rows (Fig. 9). Brush extends posteriorly to about one sixth of the body length and, in addition, is connected with only one somatic kinety (Figs. 7, 9, 14, 15). Silverline system (after Chatton-Lwoff method) widely meshed, consists of a so-called "interkinetal line" (IkL)
between two kineties and oblique lines (TL) between kinetosomes (Figs. 12, 19). Interkinetalline runs parallel along kineties and evidently close to their left. Meshes rhombus-shaped, neighboring rhombuses sometimes connect each other (Figs. 12, 19). Discussion This ciliate was first described by Kahl [35] as Trachelocerca trepida. Borror [9] redescribed it and transferred it to the genus Enchelyoden. The infraciliature and the silverline system was later studied by Agamaliev [2] and Wilbert and Kahan [44]. Compared with the original description the pellicle of my population is wholly smooth and the body shape has little or no flattening. With its characteristic ciliation, body shape, macronucleus and especially the contractile neck region it can be easily recognized. Protargol preparations reveal that the infraciliature of my population is consistent with the findings of Wilbert and Kahan [44] though their animals possess less somatic kineties (18 only). Without explanation Wilbert and Kahan [44] depicted the silverline system (stained with AgN0 3 ?) as somewhat hexagonal-shaped, and more or less like that of Prorodon ovum (s. Foissner [19])with the silverlines "crossing" the kinetosomes. In contrast with that the silverline system of the form studied here is widely meshed and the kinetosomes are never connected by silverlines (Figs. 12, 19). It is unknown whether this diversity is due to different methods of preparation or because of an optical illusion since my protargol impregnated cells sometimes also hive irregular lines between the kinetics connecting kinetosomes (transverse microtubules? Fig. 11). On the basis of studies made during the last decades, a dorsal bru sh and toxicysts are present in almost all haptorids [3-8, 10, 14, 16, 17,20-33, 37-39,41,42,45, 46]. At present, these characters are still used for taxonomic purposes at the ordinal rank, though those structures can be present in some prostomate groups, too.
Table 1. Morphometric characterization of Pseudotrachelocerca trepida. All data are based on protargol-impregnated specimens. CV = coefficient of variation in %, Max = ~aximum, Min = minimum, n = number of investigated individuals, SD = standard deviation, SE = standard error of the mean, X = arithmetic mean Character
Min
Max
X
SD
SE
CV
n
Body, length in urn Body, width in urn Macronucleus, width in urn Length of extrusome in urn Length of cilium in urn Number of macronucleus Number of basal body pairs in circumoral kinery Number of somatic kineties Number of basal bodies in each condensed ciliature band around the cytostome (PoK) Number of basal bodies per 10 urn in middle region of body Number of contractile vacuoles
84 20 5 2 5 1 19 26 5
132 32 8 4 8 1 26 33 5
105.0 24.5 5.9
15.20 3.93 1.05
4.22 1.09 0.35
14.5 16.1 17.9
1 21.3 27.6 5
0
0
0
1.75
0.53
6.4
13 13 9 9 5 19 6 11 > 20
8
13
10.2
1.56
0.38
15.3
17
1
1
0
0
0
> 20
Redescription of Pseudotrachelocerca trepida . 165
However, the silverline system, according to the new findings available, is rather order-special within the class Kinetofragminophora [23]. Generally, the silverline system of this class can be divided into two groups: fine meshed and check-shaped. The former is almost Haptoriacharacteristic while the latter is typical for other Gymno stomata-orders. But, a check-shaped system might also be present in some haptorid families e.g. Spathidiidae, Trachelophyllidae, Enchelyidae, Didiniidae etc. [7, 23]. Indeed, the silverline system of P. trepida, which should be considered to be a kind of (widely) meshed form, is quite peculiar. It is, however, not the same as that of some prostomate ciliates (e.g. Prorodon ovum [19]): the silverline is only around the kinetosomes but not "through" them. Based on the fact that P. trepida shows most characters of Haptoria, the classification of this species in Haptoria is most probably correct. Acknowledgements This study was supported by the "Fund of Natural Science of Shan dong Provence". The help of the following colleagues is greatly acknowledged: M. A. Miss. Ferry who corrected the English draft. Prof. Meng Quingxian who drew my attention to this marine organism. My special thanks to Prof. Dr. Wilhelm Foissner for his construtive criticism during my work.
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108, 264-297. 19 Foissner W. (1983 a): Taxonomische Studien tiber die Ciliaten des GroSglocknergebietes (Hohe Tauern, Osterreich), I. Familien Holophryidae, Prorodontidae, Plagiocampidae, Cole pidae, Enchelyidae und Lacrymatiidae nov. fam. Annln. naturh. Mus. Wien, 84/B, 49-85. 20 Foissner W. (1983b): Morphologie und Infraciliatur zweier ectocommensaler Ciliaten (Protozoa: Ciliophora) von Cyprinus carpio L. (Pisces: Cypriniformes): Heteropolaria lwoffi (Faure-Frerniet, 1943) (Peritrichida: Epistylididae) und ihr Predator Pseudoamphileptus macrostoma (Chen, 1955) nov. gen. (Pleurostomatida: Amphileptidae). Zoo!' lb. Syst.,
110,399-418. 21 Foissner W. (1984a): Infraciliatur, Silberliniensystem und Biometrie einiger neuer und wenig bekannter terrestrischer, limnischer und mariner Ciliaten (Protozoa: Ciliophora) aus den Klassen Kinetofragminophora, Colpodea und Polyhymenophora. Stapfia, Linz, 12, 1-165. 22 Foissner W. (1984b): Taxonomie und Okologie einiger Ciliaten (Protozoa, Ciliophora) des Saprobiensystems. I. Genera Litonotus, Amphileptus, Opisthodon. Hydrobiologia, 119, 193-208. 23 Foissner W. (1987): Neue terrestrische und limnische Ciliaten (Protozoa, Ciliophora) aus Osterreich und Deutschland. Sber. Akad. Wiss. Wien, 195,217-268. 24 Foissner W. and Foissner I. (1985): Oral monokinetids in the free-living haptorid ciliate Enchelydium polynucleatum (Ciliophora, Enchelyidae): ultrastructural evidence and phylogenetic implications. J. Protozoo!., 32, 712-722. 25 Foissner W. and Foissner I. (1988): The fine structure of Fuscheria terricola Berger et a!', 1983 and a proposed new classification of the subclass Haptoria Corliss, 1974 (Ciliophora, Litostomatea). Arch. Protistenkd., 135, 213-235. 26 Golinska K. (1971): Comparative studies on the morphology of Dileptus anatinus sp. n. (Holotricha, Gymnostomata). Acta Protozoo!., 8, 367-378. 27 Golinska K. (1986): Modifications of size and pattern of microtubular organelles in overfed cells of a ciliate Dileptus. J. Embryo!. expo Morph., 93, 85-104. 28 Groliere C. A. (1977): Contribution a I'etudc des Cilics des sphaignes et des etendues d'eau acides. I. Description de quelques especes de gymnostomes, hypostomes, hyrnenostomes et heterotriches. Ann. Stat. Bio!' Besse-en-Chandesse, 10, 265-297. 29 Hausmann K. (1973): Cytologische Studien an Trichocysten. VIII. Feinstruktur und Funktionsweise der Toxicysten von Loxophyllum meleagris und Prorodon teres. Z. Zellforsch.,
140,235-259. 30 Hausmann K. (1977): Elektronenmikroskopische Untersuchungen an den Konocysten von Loxophyllum meleagris
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31 32
33
34 35 36 37 38
Dujardin (Euciliata, Holotricha). Arch. Protistenkd ., 119, 233-238. Hausmann K.(1978): Extrusive organelles in protists. Int. Rev. Cytol., 52, 197-276. Holt P. A., Lynn D. H. and Corliss J. O. (1973): An ultrastructural study of the tentacle-bearing ciliate Actinobo/ina smalli n. sp. and its systematic and phylogenetic implications. Protistologica, 9, 521-541. Huttenlauch I. and Bardele C. F. (1987): Light and electronmicroscopical observations on the stomatogenesis of the ciliate Colepsamphacanthus Ehrenberg, 1833. J. Protozool., 34, 183-192. Jankowski A. W. (1967): New genera and subgenera of classes Gymnostomea and Ciliostomea. Mat. V. Konf. Mold. Zool., 1-36. Kahl A. (1930): Urtiere oder Protozoa. I. Wimpertiere oder Ciliata (Infusoria). I. Allgemeiner Teil und Prostornata. Tierwelt Dtl., 18, 1-180. Kink J. (1973): The organisation of fibrillar structures in the trophic and encysted Dileptus visscheri (Ciliata, Rhabdophorina). Acta Protozool., 12, 173-194. Lynn D. H. (1985): Cortical ultrastructure of Coleps bicuspis Noland, 1925 and the phylogeny of the class Prostomatea (Ciliophora). BioSystems, 18,387-397. Puytorac P. de et Grain J. (1976): Ultrastructure du cortex buccal et evolution chez les Cilies, Protistologica, 12, 49-67.
39 Raikov I. B. and Kovaleva V. G. (1980): Fine structure of the circumoral ciliature and pharyngeal apparatus of the marine ciliate Helicoprorodon gigans (Gymnostomata). Protistologica, 16, 177-198. 40 Small E. B. and Lynn D. H. (1981): A new macrosystem for the phylum Ciliophora Doflein, 1901. BioSystems, 14, 387..;.401. 41 Song W., Packroff G. und Wilbert N. (1988): Morphologic und Infraciliatur von Dileptus orientalis sp. n., einem Bodenciliaten aus Qingdao, China . Acta Protozool., 27, 271-277. 42 Song W. und Wilbert N. (1989): Taxonomische Untersuchungen an Aufwuchsciliaten (Protozoa, Ciliophora) im Poppelsdorfer Weiher, Bonn. Lauterbornia, 3, 2-221. 43 Wilbert N. (1975): Eine verbesserte Technik der Protargolimpragnation fur Ciliatcn, Mikrokosmos, 6, 171-179. 44 WilbertN. and Kahan D. (1981): Ciliates of Solar Lake on the Red Sea shore. Arch. Protistenkd., 124, 70-95. 45 Williams D. B., Williams B. D. and Hogan B. K. (1981): Ultrastructure of the somatic cortex of the gymnostome ciliate Spathidium spatbula (0. F. Muller). J. Protozool., 28, 90-99. 46 Wirnsberger E., Foissner W. und Adam H. (1984) : Morphologie und Infraciliatur von Perispira pyriformis nov. spec., Cranotheridium [oliosus (Foissner, 1983) nov. comb. und Dileptus anser (0. F. Muller, 1786) (Protozoa: Ciliophora). Arch. Protistenkd., 128, 305-317.
Key words: Ciliophora - Haptoria - Pseudotrachelocerca nov. gen., nov. comb. - Pseudotrachelocercidae nov. fam. Protozoa Weibo Song, College of Fisheries, Ocean University of Qingdao, Qingdao 266003, People's Republic of China
Eu ropean Journ al of
PROTISTOLOGY
Infraciliature and Silverline System of the Ciliate Pseudotrachelocerca trepida (Kahl, 1928), nov. gen., nov comb., and Establishment of a New Family, the Pseudotrachelocercidae nov fam. (Ciliophora, Haptoria) Weibo Song College of Fisheries, Ocean University of Qingdao, Qingdao, People's Republic of China
SUMMARY The morphology, infra ciliature and silverline system of Trachelocerca trepida Kahl, 192 8 has been reinvestigated. The species was found in marine water (Yellow Sea) near Shanghai, Eastchina. Sta ined specimens (protargo l) are characterized morphometr ically. The shape of the extrusomes (tox icysts) and the structure of oral as well as somatic kinetids indicate that this species must be sepa rated from the genus Trachelocerca. A new genus, Pseudotrachelocerca, characterized by an extensible neck, spindle-like toxicysts, irregular dorsal brush and widely meshed sliverline system, is thus erected. Based on the parti cular dorsal brush and silverline system the new family Pseudotra chelocercidae, nov. fam. is established. It can be possibly placed in the subclass Haptoria, ord er Spathidiida. However, a definite classification has to await fine structural investigations.
Introduction Mo st of our knowledge of the Kinetofr agminoph or a taxonomy comes from investigations performed with traditional methods and, above all, from the observation of living cells only. This is, however, frequently insufficient to give a clear classification of these extremely diverse carnivores. A still unr esolved question is which characteristics can be used as key for a natural classification. In recent years much weight has been put on the ora l apparatus, nematodesmata and silverline system [4, 5, 18-21, 23, 36, 42J because of the similarity of genera l kinetid structure within the class. Ne w studies strongly support higher categories and more taxa for the Haptoria [34], because all evidence indicates that those "pr imitive" kinetofragminophoran ciliates are much more differentiated than earlier work ers supposed. 093 2-4 73 9/90/002 6-0160 $3.50/0
Material and Methods Small numbe rs of Pseudotrachelocerca trepida were found in a seawa ter sample in Sheya ng County, near Shanghai, Eastchina. Th ey were culture d in a petri dish with wheat grains and distilled sea water (salinity ca. 27%0). Observation on living cells was carried out with a microscope equipped with ph ase-contrast optics. For revealing the infraciliature the protargol silver sta ining method according to Wilbert [43] was used. The silverline system was studied in specimens impregnated by the Chatton-Lwoff silver method as modified by Corliss [11]. All measurements and draw ings were perform ed at a magnification of 1600 x with vario us instrum ents. The termin ology is accord ing to Kahl [35], Corliss [12], Foissner [21] and Berger et al. [4]. The classification is after Small & Lynn [40 ] and Foissner & Foissner [25]. Th e following abbreviations are used in the figures: © 1990 by Gustav Fischer Verlag, Stuttgart
Redescription of Pseudotrachelocerca trepida . 161 ApF BB CoC CoK Cs CV DB Ex FV IkL Ma Nd OB PoK SK TI TMt Tox
= argyrophilic fiber =
=
= = =
= = =
= = = =
= = = =
=
basal body circumoral ciliature circumoral kinety cytostome contractile vacuole dorsal brush extrusome food vacuoles interkinetal silverline macronucleus nematodesmata oral bulge pararal kinetids somatic kinety transverse silverline transverse microtubules toxicysts
Results Subclass Haptoria Corliss, 1974 Order Spathidiida Foissner & Foissner, 1988 Family Pseudotrachelocercidae nov. fam.
Diagnosis. Cylindrical or bottle-shaped Spathidiina with meridional somatic kineties; dorsal brush irregular, consists of densely spaced basal body pairs not arranged in rows and connected posteriorly with only a single kinety; silverline system widely meshed. Type genus: Pseudotrachelocerca nov. gen. According to Foissner & Foissner [25], the diagnosis of the Order Spathidiida Foissner & Foissner, 1988 is "Cytostome apical, round or slit-like, in suborder Didiniina on top of cone-like proboscis; rhabdos made of three microtubular components: transverse ribbons originating from the nonciliated kinetosomes of the oral dikinetids, nematodesmal bundles originating exclusively from the same source, and bulge microtubules; somatic ciliation uniform or limited to dense bands which, however, rest within longitudinally running kineties composed of nonciliated kinetids; dorsal brush composed of 2 to many kineties; toxicysts localized, typically in or near oral area; free-living" . It is not clear yet, whether the situation of the dorsal brush is a "key" character for the order; if so the diagnosis must be changed a little to include taxa having a dorsal brush "connected" with only one somatic kinety, or a new order should probably be erected for the new family. In the suborder Spathidiina four families are placed [25]: Spathidiidae Kahl in Doflein and Reichenow, 1929, Trachelophyllidae Kent, 1882, Lacrymariidae Fromentel, 1876, and Homalozoonidae Jankowski, 1980. The new family studied here differs from the other ones, especially from the Trachelophyllidae, by its band-like condensed monokinetids around the cytostome, the dorsal brush and the widely meshed silverline system.
Genus Pseudotrachelocerca nov. gen.
Diagnosis. Pseudotrachelocercidae with a somewhat extensible neck and short rod- or spindle-like extrusomes (toxicysts) localized typically in or near oral area; cytostome apical, elliptical; nematodes mal bundles originating from oral dikinetids (circumoral kinety); somatic kineties anteriorly with "paroral" monokinetids; dorsal brush and silverline system with characteristics of the family (see above). Type-species: Pseudotrachelocerca trepida (Kahl, 1928) nov. comb. Dragesco [15] investigated a new marine ciliate (Paraspathidium obliquum) and furthermore, erected a new genus, Paraspathidium, due to the existence of "trichites" within the cytopharynx. Its infraciliature was later described by Agamaliev [1]. More or less like Pseudotrachelocerca trepida, it also possesses densely arranged kinetids which are anteriorly around the cytostome and has, as the author pictured, probably two fragments of circumoral kinety (?or anterior ends of toxicysts ?). Unfortunately, the silverline system and dorsal brush of Paraspathidium obliquum remain unknown, and a comparison between Paraspathidium and Pseudotrachelocerca is therefore impossible. Another marine genus, Trachelocerca, as redescribed by Dragesco [13], is equipped with very long, distinct "fibrils" (toxicysts? trichites?) in the oral region, and has many node-like bumps on its bulge. Until now, a detailed morphological investigation of the infraciliature, as far as I know, has not been performed. Hence, the new genus can be merely separated from Trachelocerca morphologically because of the absence of distinctive trichitelike structures in Pseudotrachelocerca.
Pseudotrachelocerca trepida (Kahl, 1928) nov. comb. (Figs. 1-19) Syn. Trachelocerca trepida Kahl, 1928 Enchelyoden trepida (Kahl, 1928) Borror, 1965
New diagnosis. In vivo about 80-160 X 30 urn; neck region somewhat contractile; body bottle-shaped, sometimes slightly flattened dorsoventrally. Macronucleus Uor S-shaped; single contractile vacuole posteriorly; Extrusomes (toxicysts) genus-specific, mostly around the cytostome; 28 meridional somatic kineties on average. Redescription. Body shape in vivo moderately variable, anterior third neck-like narrowed, can be slightly curved in all directions. Anterior end more or less coned but not truncated as depicted by Kahl [35]; posteriorly rounded, sometimes bag-like. Oral opening oval to long elliptic, lies polar on small, indistinct oral bulge (Fig. 10), hardly recognizable in vivo. Nematodesmata not recognizable in vivo. Cilia ca. 5-8!-lm long, which at the oral end (circumoral ciliation) increase to ca. 10 urn and, like that of Phialina, form a tuft with 5 girdles of cilia and beat anteriorly when feeding. Cilia of dorsal brush about 4-5 urn, very difficult to recognize in living cells.
162 . Song
5
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··:·.;":,7:·.~ ~-: .. :...:. "\ " "'. ':. : : : .;::" -
(V
'~<:;~~:." .:~.>_:-
- ( VP
6
Figs. 1- 7. Morphol ogy of Pseudotrachelocerca trepida from life (Figs. 1-4) and from protargol-impregnated specimens (Figs. 5 - 7). Figs. 1-4. Various individuals. - Fig. 5. Extrusomes (toxicysts). - Fig. 6. Ventral view. - Fig. 7. Dorsal view.
~;;:----OB
10pm
10
9
11
Figs. 8- 12. Morphology of Pseudotrachelocerca trepida from protargol-impregn ated specimens (Figs. 8- 11) and after Charron-Lwoff method (Fig. 12). - Fig. 8. Lateral view. - Fig. 9. Dorsal view of the anterior region. - Fig. 10. View of the anterior pole. Fig. 11. Argentoph ilic granules (fiber system?)after protargol-impregnation. - Fig. 12. Part of the silverline system, the arrow points to the interkinetal silverline.
13
Figs. 13-19. M orphology of Pseud otrachelocerca trepida. Light micrographs of Pseudotra chelocerca trepida (a bbrevia tions see th e text). - Fig. 13. Protar gol- impregnated specimen, show ing th e densely grouped paroral ki netids (poK ) around the cytostome. N ote th e heav ily impregnat ed gra nules (chro matin ?) within th e mac ronucleus (M a) . - Figs. 14, 15. Anterior parts of specimens, th e arrow indicates the dorsal brush. - Fig. 16. Extrusornes (Toxicysts), - Fig. 17. Ventral view of a specimen, showing the nernat od esrnal bundles (Nd). - Fig. 18. Infraciliature in anterior reg ion of th e cell (after protargol imp regnat ion ) showing the circumor al kin ety (a rro w ). - Fig. 19. Silverlin e system after Chatton-Lwoff meth od.
164 . Song
Pellicle thin and smooth, not indented by ciliary rows as described by Kahl [35]; beneath pellicle no special granules recognisable. Extrusomes occur both aro und cytostome and within cytoplasm, short rod- or spindle-shaped, often heavily stained with protargol (Figs. 5, 8). Cytoplasm very hyaline, colorless, usually densely filled with numerous dark grey, ca. 2/lm particles (Fig. 1). Macronucleus usually horseshoe-shaped, centrally located, with numerous nucleoli; micronucleus not found, presumably too near to macronucleus. Movement moderately rapid, usually swimming ahead in straigh t line while rotating around longitudinal body axis. Feeds possibly mainly on bacteria both in nature and in culture . Somatic kineties course longitudinally, composed of monokinetids; distance between basal bodies smaller anter iorly th an posteriorly (Figs. 6, 7). After protargol impregnation a fiber running along each kinety is often noticeable (Fig. 11). At base of oral bulge a circumoral kinety composed of dikinetids is present (Figs. 9, 10, 18); the number of the basal body pairs of this kinety is smaller than that of somatic kinetics (Tab. 1). Dikinetids obliquely arranged, the anterior basal body of each bears a nematodesmal bundle ("outer rhabdos" ?). 5 basal bodies distinctly condensed at anterior end of each kinety thus forming a kinetosome band which surrounds the cytostome (POK in Figs. 6, 9, 10, 13). From those condensed kinetids, which run often slightly at an angle to somatic kineties, no nematodesmata originate. After protargol impregnation the rhabdos is composed of, very probably, only one component: the nematodesmal bundles which originate from the anterior kinetosomes of the oral dikinetids (CoK in Figs. 9, 17). Dorsal brush very characteristic: made up of many basal body pairs which arc "piled up" irregularly, unlike those in other haptoridfamilies, where it forms regular rows (Fig. 9). Brush extends posteriorly to about one sixth of the body length and, in addition, is connected with only one somatic kinety (Figs. 7, 9, 14, 15). Silverline system (after Chatton-Lwoff method) widely meshed, consists of a so-called "interkinetal line" (IkL)
between two kineties and oblique lines (TL) between kinetosomes (Figs. 12, 19). Interkinetalline runs parallel along kineties and evidently close to their left. Meshes rhombus-shaped, neighboring rhombuses sometimes connect each other (Figs. 12, 19). Discussion This ciliate was first described by Kahl [35] as Trachelocerca trepida. Borror [9] redescribed it and transferred it to the genus Enchelyoden. The infraciliature and the silverline system was later studied by Agamaliev [2] and Wilbert and Kahan [44]. Compared with the original description the pellicle of my population is wholly smooth and the body shape has little or no flattening. With its characteristic ciliation, body shape, macronucleus and especially the contractile neck region it can be easily recognized. Protargol preparations reveal that the infraciliature of my population is consistent with the findings of Wilbert and Kahan [44] though their animals possess less somatic kineties (18 only). Without explanation Wilbert and Kahan [44] depicted the silverline system (stained with AgN0 3 ?) as somewhat hexagonal-shaped, and more or less like that of Prorodon ovum (s. Foissner [19])with the silverlines "crossing" the kinetosomes. In contrast with that the silverline system of the form studied here is widely meshed and the kinetosomes are never connected by silverlines (Figs. 12, 19). It is unknown whether this diversity is due to different methods of preparation or because of an optical illusion since my protargol impregnated cells sometimes also hive irregular lines between the kinetics connecting kinetosomes (transverse microtubules? Fig. 11). On the basis of studies made during the last decades, a dorsal bru sh and toxicysts are present in almost all haptorids [3-8, 10, 14, 16, 17,20-33, 37-39,41,42,45, 46]. At present, these characters are still used for taxonomic purposes at the ordinal rank, though those structures can be present in some prostomate groups, too.
Table 1. Morphometric characterization of Pseudotrachelocerca trepida. All data are based on protargol-impregnated specimens. CV = coefficient of variation in %, Max = ~aximum, Min = minimum, n = number of investigated individuals, SD = standard deviation, SE = standard error of the mean, X = arithmetic mean Character
Min
Max
X
SD
SE
CV
n
Body, length in urn Body, width in urn Macronucleus, width in urn Length of extrusome in urn Length of cilium in urn Number of macronucleus Number of basal body pairs in circumoral kinery Number of somatic kineties Number of basal bodies in each condensed ciliature band around the cytostome (PoK) Number of basal bodies per 10 urn in middle region of body Number of contractile vacuoles
84 20 5 2 5 1 19 26 5
132 32 8 4 8 1 26 33 5
105.0 24.5 5.9
15.20 3.93 1.05
4.22 1.09 0.35
14.5 16.1 17.9
1 21.3 27.6 5
0
0
0
1.75
0.53
6.4
13 13 9 9 5 19 6 11 > 20
8
13
10.2
1.56
0.38
15.3
17
1
1
0
0
0
> 20
Redescription of Pseudotrachelocerca trepida . 165
However, the silverline system, according to the new findings available, is rather order-special within the class Kinetofragminophora [23]. Generally, the silverline system of this class can be divided into two groups: fine meshed and check-shaped. The former is almost Haptoriacharacteristic while the latter is typical for other Gymno stomata-orders. But, a check-shaped system might also be present in some haptorid families e.g. Spathidiidae, Trachelophyllidae, Enchelyidae, Didiniidae etc. [7, 23]. Indeed, the silverline system of P. trepida, which should be considered to be a kind of (widely) meshed form, is quite peculiar. It is, however, not the same as that of some prostomate ciliates (e.g. Prorodon ovum [19]): the silverline is only around the kinetosomes but not "through" them. Based on the fact that P. trepida shows most characters of Haptoria, the classification of this species in Haptoria is most probably correct. Acknowledgements This study was supported by the "Fund of Natural Science of Shan dong Provence". The help of the following colleagues is greatly acknowledged: M. A. Miss. Ferry who corrected the English draft. Prof. Meng Quingxian who drew my attention to this marine organism. My special thanks to Prof. Dr. Wilhelm Foissner for his construtive criticism during my work.
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Key words: Ciliophora - Haptoria - Pseudotrachelocerca nov. gen., nov. comb. - Pseudotrachelocercidae nov. fam. Protozoa Weibo Song, College of Fisheries, Ocean University of Qingdao, Qingdao 266003, People's Republic of China