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OBJECTIVE The aim of this study was to investigate the gill filaments of Labeo bata in India parasitologically and to describe the new Myxozoa parasite species, Myxobolus leafa sp. nov., which was determined. METHODS Fish were collected alive from fish farms from Manipur (India). Sporogonic plasmodia were removed with sterile forceps and observed under phase contrast microscope. For permanent preparations, air dried smears were stained with Giemsa after fixation in acetone free absolute methanol. RESULTS Mature spores of the new species appear as leaf-like structures in valvular or frontal view, tapering at both ends. The anterior end of the spore is broader than the posterior end. Spores measure 15.3-11.8 μm (16.91 ± 1.16) in length and 13.6-15.3 μm (14.15 ± 0.67) in breadth. CONCLUSION The new gill parasite species, Myxobolus leafa sp. nov., was described from fish in India. The prevalence of the parasite was 3.3% and two stages (cyst and spore) of the parasite existed in its life cycle.

A comprehensive icthyoparasotological survey among estuarine and freshwater fishes of West Bengal, India revealed Trichodinella sunderbanensis sp. nov. and Trichodina acuta Lom, 1961 from an estuarine fish Mystus gulio (Hamilton, 1822) from the Vidyadhari river; Trichodina nandusi sp. nov. from a freshwater fish, Nandus nandus (Hamilton-Buchanan); Chilodonella hexasticha (Kiernik, 1909) Kahl, 1931 from freshwater fishes Labeo rohita (Hamilton, 1822); and Cyprinus carpio Linnaeus, 1758 from the Rupnarayan river. Taxonomic description of all the species based on wet silver nitrate impregnation method along with additional comments based on scanning electron microscopic descriptions of T. nandusi sp. nov. are also provided in this paper. Prevalence rate, morphometric parameters and comparisons with closely related species are also discussed.

Abstract A new species of the genus Thelohanellus Kudo, 1933 is described from the gills of Labeo rohita. Thelohanellus anilae sp. n. occurs in two morphometrically dissimilar forms which are described as microspore and macrospore of the same species.

Oreochromis mossambicus (Peters 1852) and Oreochromis niloticus niloticus Linnaeus, 1758 are two popular freshwater fishes introduced from Africa to India. There are many records of different species of trichodinid ectoparasites infesting wild and cultured cichlids in Africa, but no such study has been conducted on this parasitic group in India. The fishes Oreochromis mossambicus and Oreochromis niloticus niloticus were investigated for the occurrence of trichodinid ciliophorans. Oreochromis mossambicus was found positive for two species, viz., Trichodina centrostrigeata Basson, Van As & Paperna, 1983 and Paratrichodina africana Kazubski & El-Tantawy, 1986. Oreochromis niloticus niloticus was found not to be infested with any species of trichodinid ciliophorans, although, interestingly, Paratrichodina africana was first discovered in this host fish. Comparative descriptions and prevalence of these two above-mentioned species are presented.

Abstract Surveys of acephaline gregarines from Nadia district (23°N, 88.5°E) of West Bengal, India revealed the occurrence of two new species of Nematocystis Hessé, 1909; Nematocystis gardenica sp.n. and Nematocystis kalyaniensis sp. n. in the seminal vesicles of earthworms, Amynthas diffriengens (Bairds, 1809) and Amynthas hawayanus (Rosa, 1891), respectively. Trophozoites of Nematocystis gardenica sp. n. are elongate, nematode-like and have parallel sides with pointed tips. Dimensions of trophozoites ranged from 110 to 1320 (505.0 ± 12.0) μm. Dimensions of gametocysts ranged from 140 to 166 μm and the small biconical sporocysts have varying dimensions of 11.0−12.6 μm × 4.0 μm. Trophozoites of Nematocystis kalyaniensis sp.n. are solitary, elongate, nematode-like but have nearly equal bulb-like swellings at two ends, one of which lodges the nucleus. Dimension of trophozoites ranged from 246 to 1232 (565.0 ± 21.0) μm. Dimensions of gametocysts ranged from 120 to 155 μm. Sporocysts are biconical with dimensions of 8.5−11.4 × 5.0 μm.

Surveys of acephaline gregarines infesting earthworms from Senchal of Darjeeling and Ranaghat of Nadia districts of West Bengal, India revealed the occurrence of two new species of Monocystis Stein, 1848. Monocystis darjeelingensis sp.n. was found in the coelomic fluid of the earthworm Amynthus robusta Perrier, 1892 from Senchal, Darjeeling, and M. ranaghatensis sp.n. in the seminal vesicles of the earthworm Eutyphoeus valtoni (Michaelsen) from Ranaghat. Trophozoites of M. darjeelingensis sp.n. are cylindroid in shape: 210.0-273.0 (231.0 ± 2.0) × 84.0-140.0 (98.0 ± 1.8) μm; spherical gametocyst: 147.0-163.0 (156.0 ± 0.4) μm; navicular oocyst: 15.4-18.0 (17.0 ± 1.0) × 8.0-9.0 (8.2 ± 0.5) μm. Trophozoites of M. ranaghatensis sp.n. are napiform, having a nearly spheroid to ellipsoid or ovoid body, 119.0-167.0 (124.0 ± 11.0) × 57.0-84.0 (62.0 ± 1.9) μm with a prominent tail like structure at the posterior end and ellipsoidal nucleus, 9.022.0 (12.0 ± 0.4) × 9.0-13.0 (10.0 ± 1.5) μm. Gametocysts are egg-shaped, measuring 95.0-124.0 (105.0 ± 0.9) μm. Oocysts are biconical, measuring 7.6-10.1 ( 9.3 ± 1.1) × 4.1-5.6 (4.5 ± 1.3) μm.

West Bengal, situated in the eastern part of the country, is one of the most beautiful and important states of India. In a developing country like India, fish is one of the cheapest sources of protein and West Bengal contributes a major portion of the total fish production. Fishery development represents a vital sector in West Bengal. The degree of success in this sector depends to a great extent on the advancement of fish parasitology research, as it is evident that the increase of fish yields can only be achieved from healthy fish stock. During an investigation (July 2001 - December 2002), a protozoan ectoparasite, Chilodonella hexasticha (Kiernik, 1909) Kahl, 1931, was found on the gills of a freshwater fish Nandus nandus (Hamilton). This finding is very important for the fishery sector, as this parasite causes the disease chilodonellosis, which leads to mass mortality. The present paper deals with the morphology, systematics, seasonal incidences and prevalence of C. hexasticha.

Two new species of the genus Trichodina Ehrenberg, 1838, T. silondiata sp. nov. and T. pangasi sp. nov. from the gills of freshwater fish Silonia silondia (Hamilton 1822) and Pangasius pangasius (Hamilton-Buchanan) respectively from the river Ganges of West Bengal are described here. Wet smears of gills and skins were prepared in the field, air dried and impregnated with Klein’s dry silver method. In case of S. silondia (Hamilton 1822) 24 out of 146 host fishes were parasitized on the gills. Infestation rate in case of P. pangasius (Hamilton-Buchanan) was not significant. From a total of 86 examined host fish, only seven were parasitized on the gills. The mean diameters of the body of the specimens of T. silondiata sp. nov. and T. pangasi sp. nov. were 32.7–60.6 (46.4 ± 6.3) μm and 38.9–54.1 (44.9 ± 3.0) μm respectively. Taxonomic and morphometric data for these ectoparasitic trichodinids based on wet silver nitrate impregnated specimens are presented.

In a survey of the endoparasitic acephaline gregarines in the Satkhira district of Bangladesh, seminal vesicles of earthworm, Metaphire posthuma were found to be infested with a new species of the genus Enterocystis Tsvetcov 1926, Enterocystis elongatum sp. nov. The new species is elongated and measures 55.3–87.8 (67.7 ± 10.3) μm in length and 33.2–37.8 (35.7 ± 1.6) μm in width. Nucleus ovoid and measures 4.4–8.8 (6.6 ± 2.2) μm in length and 4.4–6.6 (5.3 ± 1.1) μm in width. Gametocyst with two unequal sized gametocytes and measures 88.4–101.7 μm (97.9 ± 4.8) μm in length and 77.6–95.0 (86.9 ± 7.7) μm in width. Oocysts ellipsoidal and measure 13.7–19.9 (16.7 ± 2.6) μm in length and 6.6–8.8 (7.6 ± 1.1) μm in width. Prominent association or syzygy is present in life cycle.

During the course of surveys of endoparasitic aseptate gregarines in Darjeeling district of West Bengal, India, seminal vesicles of Amynthas hawayanus (Rosa 1891) found to be infested with a new species of the genus Apolocystis (Cognetti de Martiis 1923). Trophozoites are spherical or rounded and without any polar differentiation. Diameter of the trophozoite ranges from 65.4 to 126.7 (91.8 ± 17.5) μm. Nucleus diameter measures 12.2–20.4 (14.4 ± 2.2) μm. Gametocyst is round and measures 73.6–110.4 (93.3 ± 14.0) μm and contains two unequal gametocytes. Oocyst measures 7.7–10.7 (9.5 ± 0.9) μm × 3.8–5.3 (4.6 ± 0.4) μm.

Between January 2011 and March 2011 occurrence of trichodinid ciliophorans were studied in the freshwater fishes of the river Churni. The biodiversity survey revealed presence of a new species of the genus Trichodina (Ehrenberg 1830) infesting Glossogobius giuris (Hamilton-Buchanan). Another freshwater fish Labeo bata (Hamilton 1822) were found to be infested with two species of the genus Tripartiella Lom 1959: Tripartiella bulbosa (Davis 1947) Lom 1959 and T. copiosa Lom 1959. Adhesive disc size of the new Trichodina species is small measuring 30.6–46.9 (36.2 ± 3.9) μm in diameter. The centre of the disc is finely granular and transforms into dark when impregnated with silver. The overall prevalence of this species is 15.6% (12/77). Tripartiella bulbosa and T. copiosa are very small sized ciliophorans, measuring 16.7–23.8 (20.6 ± 2.2) μm and 15.2–22.4 (19.7 ± 1.9) μm in diameter, respectively.

A biodiversity survey of aseptate gregarines in earthworm hosts in the Calcutta district of West Bengal State revealed the existence of a new species of aseptate gregarine under the genus Monocystis Stein, 1848. The monocystid gregarines obtained from the earthworm host, Eutyphoeus quaripapillatus Michelsen, 1907 have been identified as a new species. The mucron was indistinct. The gamonts are elongated, ovoid, have a hood like structure at the anterior end and measure 150.1-212.4 (188.1+/-2.1) micromx66.1-112.1 (72.3+/-1.1) microm. The gametocysts are ellipsoid and measure 92.3-136.3 microm (111.2+/-2.1)x78.3-114.4 microm (82.6+/-3.6) microm. Prominent syzygy was apparent. Oocysts are navicular, measuring 14.1-22.3 (18.1+/-3.2) micromx9.1-15.2 (11.9+/-1.1) microm.

Surveys of the endoparasitic acephaline gregarines in West Bengal revealed a new species of the genus Monocystis Stein, 1848, that resides in the seminal vesicle of the earthworm Lampito mauritii. Monocystis clubae sp. nov. is characterized by a club-shaped gamont having a taillike structure at the posterior end and measures 104.0–179.0 (160.0±24.5) µm x 62.5–71.0 (64.0±6.5) µm. Shape of the gametocysts are rounded to ovoid and measures 88.0–107.0 (104.0±1.3) µm x 86.0–102.0 µm (96.0±1.9) µm in diameter. Oocysts are navicular in shape and measures 9.6–11.0 (10.4± 0.3) µm x 7.3–8.0 (7.6±0.2) µm.

As a part of an ongoing biodiversity survey of aseptate gregarine fauna of oligochaete hosts of West Bengal, an expedition was carried out in the Darjeeling district of West Bengal and most of the earthworms collected were found to be infested with a species of Monocystis Stein, 1848. The monocystid species was collected from the seminal vesicles of the earthworm and was identified as a new species, Monocystis amynthae sp. nov. The gamont of the new species is characterized by having an elongated body with broad anterior end, separated from the narrow posterior end by a prominent constriction measuring 49.0-77.0 (66.0+/-1.3) microm x 32.0-41.0 (37.0+/-2.8) microm. The gametocysts are oval-shaped, measuring 40.0-65.0 (58.0+/-2.1) microm. The oocysts are navicular, measuring 8.0-12.0 (10.5+/-1.1) microm x 4.0-6.0 (5.5+/-1.1) microm.

Biodiversity studies in search of endoparasitic acephaline gregarines revealed a new species of the genus Monocystis Stein, 1848 in the seminal vesicles of the earthworm Metaphire houlleti (Perrier) residing in alluvial soil of the district of North 24 Parganas. The new species is characterized by having bean-shaped gamonts measuring 94.0-151.0 (119.0+/-16.0) microm x 53.0-81.0(66.0+/-8.0) microm. The anterior end of the gamont is always wider than the posterior end. The mucron is always present at the wider end. The occurrence of syzygy (end to end, cauda-frontal) is a very rare feature which has been observed in the life cycle of the new species. The gametocyst is ovoid consisting of two unequal gamonts, measuring 85.0-102.0 microm (93.0+/-6.0). Oocysts are navicular in shape, measuring 6.5-11.0 (9.0+/-1.1) microm x 4.0-7.5 (5.5+/-1.9) microm.

A survey aimed at exploring the endoparasitic acephaline gregarine diversity in South-western Bengal, detected a new species of the genus Monocystis Stein, 1848, that resides in the seminal vesicles of the earthworm, Apporectodea trapezoides Duges collected in the district of Bankura from alluvial soil. Monocystis apporectodae sp. nov. is a ribbon-like organism with one or more prominent constric-tions especially in some mature forms and measures 178.0-224.0 (203.0+/-5.0) microm x 37.0-58.0 (46.0+/-1.5) microm. The extreme ends are pointed. Its gametocysts are ovoid and measure 108.0-118.0 microm (113.0+/-1.1) x 79.0-89.0 (83.0+/-1.1) microm. Oocysts are navicular in shape. The length of the oocysts ranges from 10.0-14.6 and the width, from 5.5-8.1 microm.

A bio-diversity study in search of acephaline gregarines from Sandeshkhali village under Sundarban delta of West Bengal province, India revealed a new species of Nematocystis Hessé, 1909; Nematocystis indicus sp. nov. in the seminal vesicles of earthworms Perionyx excavatus (Perrier). Gamonts are elongated, with a cylindrical main body and a short wider anterior portion that contains the small nucleus. Both the ends are gradually narrowed like a ‘V’ to a nearly pointed tip. Body length varies from 172.0–400.0 µm (mean= 257.0 ± 65.4 µm). The maximum body width ranges from 18.0–49.0 µm (mean= 25.0± 9.0). Gametocyst almost rounded ranging from 48.0–68.0 µm (mean= 56.0 ± 1.3 µm). Oocysts biconical, measuring 7.0–11.5 (mean= 9.3 ± 1.1 µm)

Surveys of acephaline gregarines infesting earthworms from Kalyani of Nadia districts of West Bengal, India revealed the occurrence of a new species of Monocystis Stein, 1848. Monocystis levinei sp. nov., found in the coelomic fluid of the earthworm. Trophozoites of M. levinei sp. nov. are elongated in shape, 145.0–175.0 (163.0±1.5) µm x 18.0–43.0 (29.0±1.1) µm with a prominent taillike protrusion at the posterior end, measuring 7.0–10.0 (7.9±7.9) µm x 1.5–3.1 (1.8±2.1) µm and rounded nucleus, measuring 14.2–26.3 (22.3±7.3) µm x 18.4–30.5 (26.4±2.6) µm. Gametocysts are ovoid in shape ranging from 130.0–163.0 (152.0± 0.4) µm, whereas oocysts are navicular in shape, ranging in size from 8.9–12.0 (10.4±1.0) µm x 5.2–7.3 (6.9±0.5) µm.