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Ultrastructural observations of Goussia lacazei (Apicomplexa, Barrouxiidae) in the centipede, Lithobius forficatus
JOURNALOFINVERTEBRATEPATHOLOGY60,69-75
(1992)
Ultrastructural Observations of Goussia lacazei (Apicomplexa, Barrouxiidae) in the Centipede, Lithobius forficatus S. J. Division
of Microbiology
and
Genetics,
School
of Science,
BALL
J. E. BURGOYNE
AND
Polytechnic
of East London,
Romford
Road,
London
El5
4L2,
United
Kingdom
Received June 13, 1991; accepted October 3, 1991
MATERIALANDMETHODS Merozoites, macrogametes, and microgamonts of the coccidian parasite Goussia lacuzei (Labbe, 1895; Levine, 1983) in the intestinal cells of the centipede, Lithobius forficutw CL), were examined by transmission electron microscopy. All these stages developed within parasitophorous vacuoles and showed features characteristic of members of the Eimeriidae found in vertebrates. The merozoites possessed a trilaminate pellicle, 36 subpellicular microtubules, micropore, mitochondria, and the typical coccidian apical organization. The uninucleate macrogametes contained rough endoplasmic reticulum, lipid vesicles, and inclusions morphologically similar to eimerian wall-forming bodies of type I. The nuclei of the microgamont were located peripherally and during early microgamete development each nucleus was associated with a mitochondrion and a prominent submembranecomplex of I5 microtubules. o 1992 Academic PPESS, IIIC. KEY WORDS: Goussia Zucazei; Lithobius forficutus; merozoite; macrogamete; macrogamont; ultrastructure.
L. forfkatus, collected from Essex, were kept separately to verify a single infection judged from the oocysts passed in the feces. Infected intestines for transmission electron microscopy (TEM) were processed by standard techniques as previously described (Ball, 1982) and sections were examined in an AEI Corinth 275 and a Philips 301 electron microscope. The procedure followed for scanning electron microscopy was that given by Ball et al. (1981). RESULTS Goussia Zacazei was identified by the size and appearance of sporulated oocysts present in freshly passed feces (Fig. 1). Meronts and Merozoites Parasites were found in the epithelial cells of the midregion of the intestine. Although the process of growth and differentiation of a sporozoite or merozoite into a meront was not seen, the final transformation to merozoites produced a marked enlargement of the host cell (Fig. 3). Adjacent host cells did not appear to be affected. Then mature merozoites were presumably released from the destroyed host cell (Fig. 2) to reinfect others. Merozoites, like all the other parasite stages, were within a parasitophorous vacuole which is enclosed by a limiting membrane (Fig. 3). In cross section up to 32 merozoites were seen per vacuole (Fig. 3). The merozoites were uninucleate with a pellicle consisting of an outer unit membrane and an inner layer of two closely applied membranes (Figs. 4 and 5). Thirty-six regularly spaced longitudinal subpellicular microtubules were present adjacent to the inner membranes (Fig. 4). The cytoplasm also contained mitochondria, electrondense bodies, and lipid vesicles (Figs. 3 and 4). The characteristic coccidian apical complex was formed by a conoid, rhoptry ductules, and at least two rhoptries surrounded by micronemes (Figs. 4 and 5).
INTRODUCTION Goussia Zacazei (Labbe, 1895; Levine, 19831, found in the centipede, Lithobius forficatus, was originally placed in the genus Bananella (Labbe, 1895) because the majority of sporulated oocysts appeared to contain three sporocysts. Later, when the normal sporocyst number was considered to be four, this species was assigned to the genus Eimeria (see Pellerdy, 1974; Levine, 1983). Because the sporocyst walls are bivalved with a longitudinal dehiscence suture between the two halves, the species has recently been transferred by Levine (1983) to the genus Goussia in the family Barrouxiidae of the coccidian suborder Eimeriorina. Members of this family are parasites of both vertebrates and invertebrates, but little is known of the ultrastructure of those found in invertebrates. The only electron microscope study reported so far was on Barrouxia ( =Barroussia) schneideri, also found in L. forficatus (see Ball, 1982). The objective of the present study was to examine the ultrastructure of the main developmental stages of G. Zacuzei found in naturally infected centipedes. 69
All
Copyright 0 1992 rights of reproduction
0022-2011/92 $4.00 by Academic Press, Inc. in any form reserved.
70
BALLANDBURGOYNE
Macrogametes The earliest macrogametes identified had relatively large nuclei with a prominent nucleolus, rough endoplasmic reticulum, mitochondria, and lipid vesicles in the cytoplasm (Fig. 6). The characteristic nucleus alone would indicate that this stage was a macrogamete and this is confirmed by the presence of developing wall-forming bodies (Fig. 6). The macrogamete is bounded by two membranes. During development, the number of lipid vesicles and wall-forming bodies increase (Fig. 7). The only wall-forming bodies seen were those that conform to the description of type I (Fig. 7 and inset). Amorphous material present in the parasitophorous vacuole was especially associated with its limiting membrane (Fig. 7). In the more mature macrogametes the amorphous material around the outer surface was extensive and revealed a lattice-like intravacuolar structure (Fig. 8). At this stage the cytoplasmic inclusions were less well preserved, possibly due to the resistant properties of the surrounding amorphous layer (Fig. 8). Microgamonts Microgamonts enclosed by a single membrane were present in various stages of development (Figs. 9-12). In the earliest stage seen, nuclei with dispersed chromatin were located peripherally within the cytoplasm (Fig. 9). During the growth phase each nucleus developed an electron-dense chromatin portion and the cytoplasm of the parasite contained numerous lipid vesicles, presumably as energy reserves (Fig. 10). In the more mature microgamont, protruded nuclei appear to be cut off by the indentation of a collar as a prelude to microgamete formation (Fig. 11). The nuclei were associated with flagella axonemes and mitochondria which had bulbous cristae (Fig. 11). Beneath the microgamont membrane near the nucleus was a submembrane complex consisting of a band of 15 microtubules (Fig. 12). The more advanced stages of microgamete development were not observed.
DISCUSSION
As is often the case when studying natural coccidian infections the lack of sequential life cycle stages does not permit a detailed description of the development of all the different forms of the parasite. Nevertheless, the results demonstrate that the ultrastructure of G. Zacazei is similar to that of the eimerian coccidia of mammals and birds (Scholtyseck, 1973; Chobotar and Scholtyseck, 1982; Ball and Pittilo, 1990). Apart from G. lacazei, only two other Goussia species have been recorded from invertebrates (Levine, 1983, 1988) and their ultrastructure has not been reported. Of the other 28 Goussia species named so far, one is found in a reptile and the remainder in fish, where nearly half multiply in extraintestinal sites and the others in the intestinal cells. From either site the vast majority of oocysts have thin or membraneous walls (Lam, 1971; Dykova and Lom, 1981; Levine, 1988). This contrasts with the coccidia, especially Eimeria spp., in terrestrial hosts where usually two types of wall-forming bodies participate in the formation of a resistant oocyst wall (Scholtyseck et al., 1969; Scholtyseek, 1973). This difference is reflected by the absence of wall-forming bodies in the macrogametes of some piscine Goussia spp., e.g., G. iroquoina (see Paterson and Desser, 1981,1984) and G. sinensis (see Baska and Molnar, 1989). Organelles resembling wall-forming bodies were observed by Paperna et al. (1986) in the macrogamonts of G. cichlidurum but their function is unknown. This situation is similar in G. Zacazei in that organelles meeting the definition of type I wallforming bodies (Scholtyseck et al., 1969) were present in the macrogamete cytoplasm but their further development was not followed. It is likely that they could help produce the thin single-layer oocyst wall. In the majority of species in the Eimeriidae there are characteristic structures in the parasitophorous vacuoles surrounding the macrogametes. These are intravacuolar folds originating from the host cell limiting membrane and intravacuolar tubules occurring at the parasite surface. The latter may be associated with the
FIGS. 1-12. Abbreviations used: A, amorphous material; C, conoid; Ch, condensed chromatin; Co, collar; Db, dense body; Er, rough endoplasmic reticulum; F, flagellum axoneme; G, Golgi complex; HN, host cell nucleus; Im, inner membrane of pellicle; L, lattice-like inclusion; Lv, lipid vesicle; M, macrogamete; m, mitochondrion; mb, membrane of parasitophorous vacuole; me, merozoite; Mi, microgamont; mn, microneme; mp, microspore; mt, microtubule; N, nucleus of parasite; nm, nuclear membrane; Nu, nucleolus; Om, outer membrane of pellicle; P, polar body; pg, polysaccharide granule; pv, parasitophorous vacuole; R, rhoptry; Rd, ductules of rhoptry; S, sporocyst; Sc, submembrane complex; Sr, sporocyst residuum; WFI, wall-forming body type I. FIG. 1. Photomicrograph of two oocysts from freshly passed centipede feces; the upper one in optical transverse section showing four sporocysts and four pairs of polar bodies; the lower in optical longitudinal section appearing trisporocystid and showing sporocyst residuum. x 1500. FIG. 2. Scanning electron micrograph of merozoites in damaged intestinal cell. x3400. FIG. 3. Transmission electron micrograph of a parasitophorous vacuole containing a meront with mature merozoites cut in transverse section showing nuclei, nucleoli, dense bodies, rhoptries, micronemes, lipid vesicles, and a microspore. x8500. FIG. 4. Transverse section of a merozoite with rhoptries, micronemes, mitochondria, subpellicular microtubules, outer membrane of pellicle, and inner double membrane of pellicle. X25,300. FIG. 5. Anterior of fully developed merozoite cut longitudinally, showing conoid, ductules of rhoptries, micronemes, and inner and outer pellicular membranes. ~33,000.
ULTRASTRUCTURE
OF Goussiu Zacazei
71
72
BALL AND BURGOYNE
FIG. 6. Young macrogamete showing large nucleolus, lipid vesicles, endoplasmic reticulum, mitochondria, and the early development of wall-forming bodies type I (WFI). x7300. FIG. 7. Developing macrogamete with lipid vesicles of two types, Golgi complex, and mature and immature WFI. Parasitophorous vacuole harboring macrogamete contains amorphous material. x5600. (Inset) Detail of WFI to show surrounding membrane (arrow). x 14,900. FIG. 8. Portion of mature macrogamete within a parasitophorous vacuole that shows a large amount of amorphorous material with lattice-like inclusions. x9700.
ULTRASTRUCTURE
FIG. FIG.
9. Section of developing microgamont 10. Maturing microgamont showing
with nuclei
OF
Goussia lacuzei
peripherally situated nuclei that have dispersed chromatin. with condensed chromatin and cytoplasm with numerous
nutrition of the parasite. None of these intravacuolar structures were present in G. Zucuzei, although the macrogamete possessed micropores. There was amorphous material in the parasitophorous vacuole around the developing macrogamete and this material considerably increased during the parasite’s growth and became associated with lattice-like inclusions. A similar
73
lipid
x5500. vesicles.
x 8500.
but not identical finding was reported by Paperna and Landsberg (1985) in G. cichlidarum, which develops in epithelial cells lining the swim bladder of cichlid fish. Before sporulation, which takes place in situ, a layer surrounding the oocyst consisted of either dense homogeneous granular substances or zones of varying electron densities containing rudiments of membranes and
BALL AND BURGOYNE
74
FIG. 11. Portion of differentiating microgamont showing nucleus, mitochondrion, collar, transverse section of a flagellum axoneme, and submembrane complex. ~27,700. FIG. 12. Part of microgamont surface showing part of a mitochondrion, section of flagellum axoneme, and microtubules of submembrane complex. ~76,700.
laminated residues. Such structures were thought to be by-products of degradation taking place in the oocyst cytoplasm during sporoblast development (Paperna and Landsberg, 1985). There are two basic configurations for the microgamonts of the coccidia: one in which invaginations and fissures are formed during growth, thereby increasing the surface area for the formation of microgametes, and the other where the microgamont remains a solid sphere (Scholtyseck et al., 1972; Ball and Pittilo, 1990). The microgamont of G. Zucazei conforms to the latter group. During the early differentiation of the microgametes a row of microtubules are formed which could be interpreted as a perforatorium-anlage that would eventually reinforce and support the tip of the microgamete (Cheissin, 1965). Short microtubules in similar numbers have been seen in other coccidia (Pelster and Piekarski, 1971; Scholtyseck et al., 1972). REFERENCES Ball, S. J. 1982. Ultrastructural observations on Barroussia deri (Apicomplexa, Eucoccidia) in the centipede Lithobius tus. J. Invertebr.
Pathol.
schneifirfica-
39, 229-235.
Ball, S. J., and Pittilo, R. M. 1990. Structure and ultrastructure. In “Coccidiosis of Man and Domestic Animals” (P. L. Long, Ed.), pp. 1741. CRC Press, Boca Raton, FL. Ball, S. J., Pittilo, R. M., Joyner, L. P., and Norton, C. C. 1981. Scan-
ning and transmission electron microscopy of Eimeria maxima microgametogenesis. Parasitology 82, 131-135. Baska, F., and Molnar, K. 1989. Ultrastructural observations on different developmental stages of Goussiu sinensis (Chen, 1955), a parasite of the silver carp (Hypophthalmichthys molitrix Valenciennes, 1844). Acta Vet. Hung. 37, 81-87. Cheissin, E. M. 1965. Electron microscopic study of microgametomagna and genesis in two species of coccidia from rabbit (Eimeria E. intestinalis). Acta Protozool. 3, 215-224. Chobotar, B., and Scholtyseck, E. 1982. Ultrastructure. In “The Biology of the Coccidia” (P. L. Long, Ed.), pp. 101-165. Univ. Park Press, Baltimore, MD. Dykova, I., and Lom, J. 1981. Fish coccidia: Critical notes on life cycles, classification and pathogenicity. J. Fish Dis. 4, 487-505. Labbe, A. 1895. Bananella lacazei genre nouveau de coccidie oligosporee. Arch. Zool. Exp. Gin. (3e serie) 3, XV-XVI. Defretinella, and Goussio Levine, N. D. 1983. The genera Barrouxia, of the coccidian family Barrouxiidae (Protozoa, Apicomplexa). J. Protozool.
30, 542-547.
Levine, N. D. 1988. “The Protozoan Phylum Apicomplexa,” Vol. 1. CRC Press, Boca Raton, FL. Lom, J. 1971. Remarks on the spore envelopes in fish coccidia. Folia Parasitol. (Praha) 18, 289-293. Paperna, I., and Landsberg, J. H. 1985. Ultrastructure of oogony and sporogony in Goussia cichlidarum, Landsberg and Paperna, 1985, a coccidian parasite in the swimbladder of cichlid fish. Protistologica 21, 349-359. Paperna, I., Landsberg, J. H., and Feinstein, N. 1986. Ultrastructure Landsberg and Paof the macrogamont of Goussia cich2idarum perna, 1985, a coccidian parasite in the swimbladder of cichlid fish. Ann. Parasitol. Hum. Comp. 61, 511620.
ULTRASTRUCTURE Paterson, W. B., and Desser, S. S. 1981. Ultrastructure of macrogametogenesis, macrogametes and young oocysts of Eimeriu iroquoina Molnar and Fernando, 1974 in experimentally infected fathead minnows @‘imep?udespromelas, Cyprinidae). J. Parasitol. 67, 496404. Paterson, W. B., and Desser, S. S. 1984. Ultrastructural observations on fertilization and sporulation in Goussin iroquoina (Molnar and Fernando, 1974) in experimentally infected fathead minnows (Pimephles promelas, Cyprinidae). J. Parasitol. 70, 703-711. Pell&dy, L. P. 1974. “Coccidia and Coccidiosis.” Parey, Berlin/Hamburg. Pelster, B., and Piekarski, G. 1971. Elektronenmikroskopische ana-
OF Goussia Zczcuzei
75
lyse de mikrogametenentwicklung bei Toxoplasma gondii. 2. Parasitenkd. 37, 267-277. Scholtyseck, E. 1973. Ultrastructure. In “The Coccidia: Eimeriu, Zsospora, Toxoplasma and Related Genera” (D. M. Hammond and P. L. Long, Eds.), pp. 81-144. Univ. Park Press, Baltimore, MD. Scholtyseck, E., Mehlhorn, H., and Hammond, D. M. 1972. Electron microscope studies of microgametogenesis in coccidia and related groups. 2. Parasitenkd. 38, 95-131. Scholtyseck, E., Rommel, A., and Heller, G. 1969. Licht-und elektronenmikroskopische untersuchungen zur bildung der oocystenhiille bei eimerien (Eimeria perforans, E. sheahe, und E. tenella). 2. Parasitenkd. 31, 289-298.
(1992)
Ultrastructural Observations of Goussia lacazei (Apicomplexa, Barrouxiidae) in the Centipede, Lithobius forficatus S. J. Division
of Microbiology
and
Genetics,
School
of Science,
BALL
J. E. BURGOYNE
AND
Polytechnic
of East London,
Romford
Road,
London
El5
4L2,
United
Kingdom
Received June 13, 1991; accepted October 3, 1991
MATERIALANDMETHODS Merozoites, macrogametes, and microgamonts of the coccidian parasite Goussia lacuzei (Labbe, 1895; Levine, 1983) in the intestinal cells of the centipede, Lithobius forficutw CL), were examined by transmission electron microscopy. All these stages developed within parasitophorous vacuoles and showed features characteristic of members of the Eimeriidae found in vertebrates. The merozoites possessed a trilaminate pellicle, 36 subpellicular microtubules, micropore, mitochondria, and the typical coccidian apical organization. The uninucleate macrogametes contained rough endoplasmic reticulum, lipid vesicles, and inclusions morphologically similar to eimerian wall-forming bodies of type I. The nuclei of the microgamont were located peripherally and during early microgamete development each nucleus was associated with a mitochondrion and a prominent submembranecomplex of I5 microtubules. o 1992 Academic PPESS, IIIC. KEY WORDS: Goussia Zucazei; Lithobius forficutus; merozoite; macrogamete; macrogamont; ultrastructure.
L. forfkatus, collected from Essex, were kept separately to verify a single infection judged from the oocysts passed in the feces. Infected intestines for transmission electron microscopy (TEM) were processed by standard techniques as previously described (Ball, 1982) and sections were examined in an AEI Corinth 275 and a Philips 301 electron microscope. The procedure followed for scanning electron microscopy was that given by Ball et al. (1981). RESULTS Goussia Zacazei was identified by the size and appearance of sporulated oocysts present in freshly passed feces (Fig. 1). Meronts and Merozoites Parasites were found in the epithelial cells of the midregion of the intestine. Although the process of growth and differentiation of a sporozoite or merozoite into a meront was not seen, the final transformation to merozoites produced a marked enlargement of the host cell (Fig. 3). Adjacent host cells did not appear to be affected. Then mature merozoites were presumably released from the destroyed host cell (Fig. 2) to reinfect others. Merozoites, like all the other parasite stages, were within a parasitophorous vacuole which is enclosed by a limiting membrane (Fig. 3). In cross section up to 32 merozoites were seen per vacuole (Fig. 3). The merozoites were uninucleate with a pellicle consisting of an outer unit membrane and an inner layer of two closely applied membranes (Figs. 4 and 5). Thirty-six regularly spaced longitudinal subpellicular microtubules were present adjacent to the inner membranes (Fig. 4). The cytoplasm also contained mitochondria, electrondense bodies, and lipid vesicles (Figs. 3 and 4). The characteristic coccidian apical complex was formed by a conoid, rhoptry ductules, and at least two rhoptries surrounded by micronemes (Figs. 4 and 5).
INTRODUCTION Goussia Zacazei (Labbe, 1895; Levine, 19831, found in the centipede, Lithobius forficatus, was originally placed in the genus Bananella (Labbe, 1895) because the majority of sporulated oocysts appeared to contain three sporocysts. Later, when the normal sporocyst number was considered to be four, this species was assigned to the genus Eimeria (see Pellerdy, 1974; Levine, 1983). Because the sporocyst walls are bivalved with a longitudinal dehiscence suture between the two halves, the species has recently been transferred by Levine (1983) to the genus Goussia in the family Barrouxiidae of the coccidian suborder Eimeriorina. Members of this family are parasites of both vertebrates and invertebrates, but little is known of the ultrastructure of those found in invertebrates. The only electron microscope study reported so far was on Barrouxia ( =Barroussia) schneideri, also found in L. forficatus (see Ball, 1982). The objective of the present study was to examine the ultrastructure of the main developmental stages of G. Zacuzei found in naturally infected centipedes. 69
All
Copyright 0 1992 rights of reproduction
0022-2011/92 $4.00 by Academic Press, Inc. in any form reserved.
70
BALLANDBURGOYNE
Macrogametes The earliest macrogametes identified had relatively large nuclei with a prominent nucleolus, rough endoplasmic reticulum, mitochondria, and lipid vesicles in the cytoplasm (Fig. 6). The characteristic nucleus alone would indicate that this stage was a macrogamete and this is confirmed by the presence of developing wall-forming bodies (Fig. 6). The macrogamete is bounded by two membranes. During development, the number of lipid vesicles and wall-forming bodies increase (Fig. 7). The only wall-forming bodies seen were those that conform to the description of type I (Fig. 7 and inset). Amorphous material present in the parasitophorous vacuole was especially associated with its limiting membrane (Fig. 7). In the more mature macrogametes the amorphous material around the outer surface was extensive and revealed a lattice-like intravacuolar structure (Fig. 8). At this stage the cytoplasmic inclusions were less well preserved, possibly due to the resistant properties of the surrounding amorphous layer (Fig. 8). Microgamonts Microgamonts enclosed by a single membrane were present in various stages of development (Figs. 9-12). In the earliest stage seen, nuclei with dispersed chromatin were located peripherally within the cytoplasm (Fig. 9). During the growth phase each nucleus developed an electron-dense chromatin portion and the cytoplasm of the parasite contained numerous lipid vesicles, presumably as energy reserves (Fig. 10). In the more mature microgamont, protruded nuclei appear to be cut off by the indentation of a collar as a prelude to microgamete formation (Fig. 11). The nuclei were associated with flagella axonemes and mitochondria which had bulbous cristae (Fig. 11). Beneath the microgamont membrane near the nucleus was a submembrane complex consisting of a band of 15 microtubules (Fig. 12). The more advanced stages of microgamete development were not observed.
DISCUSSION
As is often the case when studying natural coccidian infections the lack of sequential life cycle stages does not permit a detailed description of the development of all the different forms of the parasite. Nevertheless, the results demonstrate that the ultrastructure of G. Zacazei is similar to that of the eimerian coccidia of mammals and birds (Scholtyseck, 1973; Chobotar and Scholtyseck, 1982; Ball and Pittilo, 1990). Apart from G. lacazei, only two other Goussia species have been recorded from invertebrates (Levine, 1983, 1988) and their ultrastructure has not been reported. Of the other 28 Goussia species named so far, one is found in a reptile and the remainder in fish, where nearly half multiply in extraintestinal sites and the others in the intestinal cells. From either site the vast majority of oocysts have thin or membraneous walls (Lam, 1971; Dykova and Lom, 1981; Levine, 1988). This contrasts with the coccidia, especially Eimeria spp., in terrestrial hosts where usually two types of wall-forming bodies participate in the formation of a resistant oocyst wall (Scholtyseck et al., 1969; Scholtyseek, 1973). This difference is reflected by the absence of wall-forming bodies in the macrogametes of some piscine Goussia spp., e.g., G. iroquoina (see Paterson and Desser, 1981,1984) and G. sinensis (see Baska and Molnar, 1989). Organelles resembling wall-forming bodies were observed by Paperna et al. (1986) in the macrogamonts of G. cichlidurum but their function is unknown. This situation is similar in G. Zacazei in that organelles meeting the definition of type I wallforming bodies (Scholtyseck et al., 1969) were present in the macrogamete cytoplasm but their further development was not followed. It is likely that they could help produce the thin single-layer oocyst wall. In the majority of species in the Eimeriidae there are characteristic structures in the parasitophorous vacuoles surrounding the macrogametes. These are intravacuolar folds originating from the host cell limiting membrane and intravacuolar tubules occurring at the parasite surface. The latter may be associated with the
FIGS. 1-12. Abbreviations used: A, amorphous material; C, conoid; Ch, condensed chromatin; Co, collar; Db, dense body; Er, rough endoplasmic reticulum; F, flagellum axoneme; G, Golgi complex; HN, host cell nucleus; Im, inner membrane of pellicle; L, lattice-like inclusion; Lv, lipid vesicle; M, macrogamete; m, mitochondrion; mb, membrane of parasitophorous vacuole; me, merozoite; Mi, microgamont; mn, microneme; mp, microspore; mt, microtubule; N, nucleus of parasite; nm, nuclear membrane; Nu, nucleolus; Om, outer membrane of pellicle; P, polar body; pg, polysaccharide granule; pv, parasitophorous vacuole; R, rhoptry; Rd, ductules of rhoptry; S, sporocyst; Sc, submembrane complex; Sr, sporocyst residuum; WFI, wall-forming body type I. FIG. 1. Photomicrograph of two oocysts from freshly passed centipede feces; the upper one in optical transverse section showing four sporocysts and four pairs of polar bodies; the lower in optical longitudinal section appearing trisporocystid and showing sporocyst residuum. x 1500. FIG. 2. Scanning electron micrograph of merozoites in damaged intestinal cell. x3400. FIG. 3. Transmission electron micrograph of a parasitophorous vacuole containing a meront with mature merozoites cut in transverse section showing nuclei, nucleoli, dense bodies, rhoptries, micronemes, lipid vesicles, and a microspore. x8500. FIG. 4. Transverse section of a merozoite with rhoptries, micronemes, mitochondria, subpellicular microtubules, outer membrane of pellicle, and inner double membrane of pellicle. X25,300. FIG. 5. Anterior of fully developed merozoite cut longitudinally, showing conoid, ductules of rhoptries, micronemes, and inner and outer pellicular membranes. ~33,000.
ULTRASTRUCTURE
OF Goussiu Zacazei
71
72
BALL AND BURGOYNE
FIG. 6. Young macrogamete showing large nucleolus, lipid vesicles, endoplasmic reticulum, mitochondria, and the early development of wall-forming bodies type I (WFI). x7300. FIG. 7. Developing macrogamete with lipid vesicles of two types, Golgi complex, and mature and immature WFI. Parasitophorous vacuole harboring macrogamete contains amorphous material. x5600. (Inset) Detail of WFI to show surrounding membrane (arrow). x 14,900. FIG. 8. Portion of mature macrogamete within a parasitophorous vacuole that shows a large amount of amorphorous material with lattice-like inclusions. x9700.
ULTRASTRUCTURE
FIG. FIG.
9. Section of developing microgamont 10. Maturing microgamont showing
with nuclei
OF
Goussia lacuzei
peripherally situated nuclei that have dispersed chromatin. with condensed chromatin and cytoplasm with numerous
nutrition of the parasite. None of these intravacuolar structures were present in G. Zucuzei, although the macrogamete possessed micropores. There was amorphous material in the parasitophorous vacuole around the developing macrogamete and this material considerably increased during the parasite’s growth and became associated with lattice-like inclusions. A similar
73
lipid
x5500. vesicles.
x 8500.
but not identical finding was reported by Paperna and Landsberg (1985) in G. cichlidarum, which develops in epithelial cells lining the swim bladder of cichlid fish. Before sporulation, which takes place in situ, a layer surrounding the oocyst consisted of either dense homogeneous granular substances or zones of varying electron densities containing rudiments of membranes and
BALL AND BURGOYNE
74
FIG. 11. Portion of differentiating microgamont showing nucleus, mitochondrion, collar, transverse section of a flagellum axoneme, and submembrane complex. ~27,700. FIG. 12. Part of microgamont surface showing part of a mitochondrion, section of flagellum axoneme, and microtubules of submembrane complex. ~76,700.
laminated residues. Such structures were thought to be by-products of degradation taking place in the oocyst cytoplasm during sporoblast development (Paperna and Landsberg, 1985). There are two basic configurations for the microgamonts of the coccidia: one in which invaginations and fissures are formed during growth, thereby increasing the surface area for the formation of microgametes, and the other where the microgamont remains a solid sphere (Scholtyseck et al., 1972; Ball and Pittilo, 1990). The microgamont of G. Zucazei conforms to the latter group. During the early differentiation of the microgametes a row of microtubules are formed which could be interpreted as a perforatorium-anlage that would eventually reinforce and support the tip of the microgamete (Cheissin, 1965). Short microtubules in similar numbers have been seen in other coccidia (Pelster and Piekarski, 1971; Scholtyseck et al., 1972). REFERENCES Ball, S. J. 1982. Ultrastructural observations on Barroussia deri (Apicomplexa, Eucoccidia) in the centipede Lithobius tus. J. Invertebr.
Pathol.
schneifirfica-
39, 229-235.
Ball, S. J., and Pittilo, R. M. 1990. Structure and ultrastructure. In “Coccidiosis of Man and Domestic Animals” (P. L. Long, Ed.), pp. 1741. CRC Press, Boca Raton, FL. Ball, S. J., Pittilo, R. M., Joyner, L. P., and Norton, C. C. 1981. Scan-
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