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Protistology 4 (2), 91-95 (2005)
Protistology
Description of a new gregarine species, Zygocystis perionyxae sp. n. (Protozoa: Zygocystidae), from the earthworm Perionyxgravelleyi (Annelida: Oligochaeta) from West Bengal, India
Probir K. Bandyopadhyay and Amlan K. Mitra
Parasitology Laboratory, Department of Zoology, University of Kalyani, Kalyani, West Bengal, India
Summary
Surveys of acephaline gregarines from Canning (West Bengal, India) revealed the occurrence of a new species of Zygocystis Stein 1848 in the coelomic fluid of the earthworm Perionyx graveleyi. Its trophozoites are fusiform and are always found in syzygy. The union is effected by a convex protrusion of one trophozoite fitting into a regular concave depression of the other. There is an extended cylindrical extension at the free end. Nucleus is spherical to ellipsoid. Gametocysts are spherical; oocysts navicular.
Key words: gregarines, acephaline, earthworm, Zygocystis perionyxae sp. n.
Introduction
The genus Zygocystis Stein 1848 comprises acephaline gregarines with pyriform gamonts, always found in frontal syzygy, and navicular oocysts. Levine (1988) listed 14 species in this genus and 3 more species have been added since (Segun, 1978; Pradhan and Dasgupta, 1983, Bandyopadhyay and Mitra, 2004). Two of them, Zygocystis indicus Pradhan and Dasgupta 1983 and Z. levinei Bandyopadhyay and Mitra 2004, have been reported from Indian earthworms. The present paper contains the description of yet another Indian Zygocystis species obtained from the earthworm Perionyx graveleyi in West Bengal.
Material and Methods
Earthworms were collected and taken to the laboratory. They were dissected while alive and coelomic
fluid was collected. Preparation of slides followed the procedure described in the previous paper (Bandyopadhyay and Mitra, 2004). Observations were done under an Olympus phase contrast microscope and photomicrographs were taken using an Olympus camera.
Results
Zygocystis perionyxae sp. n. (Figs 1-8, Table 1-2)
The trophozoites form syzygy early in their development. Each trophozoite in a syzygy is fusi-form,with a broad base gradually narrowing to a funnelshaped structure at the free end. The union is effected by a convex surface of one sporont fitting into a regular hemispherical depression, about 7-8 ^m deep, of the other. The sporonts in the syzygy are generally unequal, the partner with a concave base being larger than that with the convex protrusion at the junction end.
© 2005 by Russia, Protistology
Figs 1-5. Photomicrographs of the different stages in the life history of Zygocystis perionyxae sp. n. 1 -Two young trophozoites before association; 2 - syzygy; 3 - enlarged view showing the junction of a syzygy; 4 - mature gametocyst; 5 - oocyst. Scale bars: 1, 2 - 100 ^m; 3, 4 - 25 ^m; 5 - 10 ^m.
The larger partner with a concave hemispherical depression at its base is 73.0-158.0 ^m long, with a maximum width of22.0-39.8 ^m. The smaller partner, with a convex protrusion at its base, is 66.0-136.4 ^m long, with a maximum width of 19.4-34.0 ^m. Both partners have a funnel-shaped structure at their free ends, 8.5-14.0 ^m long. The diameter of the junction is 16.6-27.9 ^m.
Ectosarc is prominent, clear and thin, about 1.01.5 ^m in thickness. The epicyte, the outer layer of the ectosarc, has longitudinal furrows, which can be discerned under the light microscope at a high magnification and proper illumination. These epicytic folds result in a striated appearance of the ectosarc. Epicytic folds are approximately 1.0 ^m apart at the widest part of the axes, but may appear oblique during locomotion. These folds decrease in number and join one another towards the narrowed free end of the trophozoite. They extend beyond the main body and form a funnel-like structure at the free end. The epicytic folds do not
converge in general, rather, they run almost parallel. No epicentre of these epicytic folds could be discerned.
The sarcocyte, below the epicyte, contains undifferentiated zone of cytoplasm. The monocyte, the third layer of the ectosarc, is not clearly defined in this species. Its presence could be observed in some cases where the nucleus is pushed at one extreme end where the ectosarc remains as thick as in the other parts. This observation allows one to speculate about the presence of a true functional myocyte that prevents any significant change of conformation.
The endosarc is granular, containing round para-glycogen granules, about 2 ^m in diameter, and many basophilic granules, about 1-2 ^m in diameter. The latter are absent in the part of the cell anterior to the nucleus.
Nucleus is spherical or ellipsoid , measuring 10.220.3 (17.3+1.2) x 9.8-16.4 (13.5+2.2) ^m. Its position is variable but it is usually located at the free end, opposite to the syzygy junction. Gametocysts are sphe-
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Figs 6-8. Camera lucida drawings of the diferent stages in the life history of Zygocystis perionyxae sp. n. 6 - Two trophozoites in syzygy; 7 - mature gameto-cyst; 8 - oocyst.
rical, 137.0-166.0 (152.0+1.5) pm; oocysts are biconical, from 7.3-9.4 (8.2+1.1) to 3.9-5.7 (4.3+1.0) pm.
Taxonomic summary
Host: Perionyx gravelleyi Area/Locality: Canning, West Bengal, India Infection locus: Coelomic fluid, posterior to the genital openings
Incidence: 6 out of 25 hosts found Materials: Holotype, slide PG-05, and paratype, slide AR-04 in the collection of the Parasitology Laboratory, Department of Zoology, University of Kalyani, Kalyani 741235, West Bengal, India.
Etymology: The species name has been derived from the generic name of the host earthworm Perionyx gravelleyi.
Discussion
The gregarine described in the present paper is a coelomic parasite of oligochaetes. It has a cylindrical body with some differentiation at the anterior end, and navicular oocysts. Therefore it can be attributed to the family Monocystidae. Presence of early and permanent syzygy justifies its inclusion into the subfamily Zygocystinae Bhatia 1930. This subfamily contains three genera: Zygocystis, Adelphocystis and Pleurocystis. The genus Pleurocystis has lateral syzygy, whereas the
Table 1. Summaryof measurements of different parts and ratios of 20 syzygies of Zygocystis perionyxae sp. n.
Different body parts (A= Large partner, B= Small partner) Range Mean Standard Deviation
Body length (BLA) - A 73.0-158.0 122.0 1.1
Body length (BLB) - B 66.0-136.4 92.0 1.7
Body width (BWA) - A 22.0-39.8 32.0 2.3
Body width (BWB) - B 19.4-34.0 28.5 1.7
Nucleus length (NLA) - A 12.3-20.3 16.9 1.1
Nucleus length (NLB) - B 10.2-16.0 14.1 2.1
Nucleus Width (NWA) - A 11.3-16.4 14.3 1.1
Nucleus Width (NWB) - B 9.8-14.6 14.5 2.6
Terminal funnel diameter 8.5-14.0 10.5 1.5
Junctional diameter 16.6-27.9 21.4 1.3
Gametocyst diameter 137.0-166.0 152.0 1.5
Oocyst length 7.3-9.4 8.2 1.1
Oocyst width 3.9-5.7 4.3 1.0
BLA/BWA 3.3-3.9 3.4 1.3
BLB/BWB 2.5-3.1 2.7 0.2
NLA/NWA 1.0-1.2 1.3 0.1
NLB/NWB 1.0-1.1 1.0 0.2
BLA/BLB 1.1-1.2 1.1 0.1
BWA/BWB 1.1-1.2 1.1 0.1
present species has frontal syzygy. Therefore, it cannot be grouped with the genus Pleurocystis. Adelpocystis has frontal syzygy but the gamonts are very active and elongate, approximately 750-1500 pm long, and as many as five or six trophozoites are often enclosed in a single membrane (Cox, 1967), while the present form is less active, much smaller and does not form any aggregations of association pairs in a common membrane. It also has another host and a different distribution. Considering these contrasting characters, the present form cannot be placed into the genus Adelphocystis. Our species has a certain similarity to some elongate species of the genus Zygocystis, viz., Zygocystis henleae (Meier, 1956) and Z. legeri (Hesse, 1909). Considering this point, it can be placed into the genus Zygocystis. However, it is different from the above two species. Z. legeri is much longer and wider than the present species, and has a pointed free end, whereas the free end in our species is extended and cylindrical. Gametocysts are spherical in our species and elliptic in Z. legeri. Moreover, the site of infection is coelom in case of the former and seminal vesicles in case of the latter. Z. henlae is a coelomic parasite with morphometric measurements close to those of our species and with spherical gametocysts. However, in Z. henlae the free ends of the association partners are blunt, the nuclei are spherical and gametocysts are smaller (75-100 pm in diameter) as compared to the present species. Moreover, the shape of trophozoites, the junction of association pairs, the host earthworm species and its locality are different. A comparison between Zygocystis legeri, Z. henlae and Z. perionyxae n. sp. is presented in Table 2.
The species under discussion is also quite different in morphology, host preference and distribution from
Table 2. Comparisons between different characters of Zygocystis legeri Hesse, 1909, Z. henleae Meier, 1956 and Zygocystis perionyxae sp. n. (all measurements are in Mm).
Species Characters Z. legeri Hesse, 1909 Z. henleae Meier, 1956 Z. perionyxae
Host(s) Allolobophora chlorotica and Pheretima diffringens Henlea ventriculosa Perionyx gravelleyi
Locality England, France, Germany and U.S.A. Germany India
Trophozoite Elongate, cylindro-conical, with pointed ends Elongate, cylindro-conical, with round ends Cylindroconical, gradually narrowing to a funnel-shaped structure at the free end
Size 172-750 by 45-150 250-300 by 30-45 66.0-158 by 19.4-34.0
Ectosarc Prominent with fine longitudinal striations converge at ends With fine longitudinal striations Prominent, longitudinally furrowed
Endosarc Granular, with large (6-12 by 3-9 Mm) paramylon reserve granules Granular, with small round (1 -2 in diameter) paramylon reserve granules Granular, with many round (approx. 2 pm) paraglycogen granules (1 -2 Mm)
Nucleus Nearly spherical with a single karyosome Round with a single karyosome Spherical or elliptical, karyosome spread out forming vacuoles
Size 25-30 in diameter 20 in diameter 10.2-20.3 by 9.8-14.6 in diameter
Association Effected through a single plane Effected through a single plane Concave, hemispherical depression fits with the convex protrusion of the other
Free end Pointed Blunt Funnel shaped
Gametocyst Ellipsoidal Rounded Spherical
Size 189 x 153, 225 x 180 75-100 137.0-166.0 in diameter
Oocyst - - Biconical
Size 15.0 x 4.5, 19.5-22.5 by 6.3-9.0 22-25.5 by 9.8-10.8 7.3-9.4 by 2.9-4.8
Reference Hesse (1909) Meier (1956) Present study
the two Zygocystis species described from India so far, Z. indicus and Z. levinei.
To sum up, the species described should be attributed to the genus Zygocystis but it is different from all the known species of this genus. Its specific character is a fusiform body with an extended cylindrical free end. Therefore, the parasite should be accommodated in a new species. We propose for it the name Zygocystis perionyxae.
The present investigation demonstrates that the study of aseptate gregarine fauna of India is far from complete. Further surveys may well reveal the presence of new gregarine species.
References
Bandyopadhyay P. and Mitra A.K. 2004. Description of a new species Zygocystis levinei sp. n. (Eugrega-rinida, Zygocystidae), from the earthworm Amynthas nicholsoni (Oligochaeta) from West Bengal, India. Protistology. 3, 227-231.
Cox F.E.G. 1967. Monocystid gregarines of Nigerian earthworms. I. Adelophocystis aeikineta gen. nov., sp. nov. from the coelom of Kefia variabilis Clausen, 1963. Parasitol. 57, 507-513.
Hesse E. 1909. Contribution a l'etude des monocys-tides des oligochetes. Archs. Zool. Exp. Gen. 43, 27301.
Levine N.D. 1988. The protozoan phylum Apico-mplexa. Vol. I. CRC Press, Inc. Boca Raton, Florida.
Meier M. 1956. Die Monocystideenfauna der oli-gochaten von Erlangen und Umgebung. Arch. Pro-tistenk. 101, 400.
Pradhan D. and Dasgupta B. 1983. Life history and morphology of Zygocystis indicus n. sp. J. Beng. Nat. Hist. Soc. (N. S.). 2, 17-23.
Segun A.O. 1978. Monocystid gregarine parasites of Nigerian earthworms. J. Protozool. 25, 157-162.
Address for correspondence: Probir K. Bandyopadhyay. Parasitology Laboratory, Department of Zoology, University of Kalyani, Kalyani 741235, West Bengal, India. E-mail: prabir0432@hotmail.com
Editorial responsibility: Andrew Dobrovolskij
