Lytocestidae Wardle et McLeod, 1952 »
Lytocestinae Satpute et Agarwal, 1980 »
Lytocestus Cohn, 1908 »
Lytocestus clariae, Tandon, Chakravarty and Das 2005
Guwahati (Assam), Shella (Meghalaya)
Body elongate, flat with no trace of internal or external segmentation, tapering at anterior end, 14.52 -32.20 mm in length, 0.53 -1.45 mm in maximum breadth at level of cirrus sac; body proper divided into cortex and inner medulla by two layers of longitudinal muscles. Scolex undifferentiated, smooth, unarmed, with bluntly tapering extremity, followed by short neck devoid of reproductive organs. Testes numerous, 270-495 in number, occupying medullary region, ovoid, larger than vitelline follicles, extending from just behind anterior follicles of vitellaria, posteriorly up to cirrus sac; cirrus sac compact, bulbous; ductus ejaculatorius opening close to female pore into shallow genital atrium. Ovary bilobed, H-shaped, follicular, extending posteriorly behind Mehlisâ€™ gland, lobes cortical in disposition and joined to each other by medullary ovarian isthmus anterior to Mehlisâ€™ gland; uterus glandular, extending in front of isthmus up to cirrus sac; vaginal tube joining uterus at distal end to open unitedly at shallow atrium. Vitelline follicles ovoid, commencing from short distance anterior to testes, extending up to level of cirrus sac, arranged in two rows lateral to testes; no post ovarian vitelline follicles present. Excretory pore terminal. Eggs 0.05 -0.07 x 0.02 -0.03 mm, oval, spinuous and operculate.
The disposition of the vitellaria in the cortex and testes in the medullary zone ascertains the inclusion of the present form in the family Lytocestidae Wardle and McLeod, 1952. Further, owing to the characters such as the presence of undifferentiated scolex, the absence of postovarian yolk glands, the uterine coils covered with a thick coat of accompanying cells and the ejaculatory duct enclosed within a compact parenchymatous bulb, the present form belongs to the genus Lytocestus Cohn, 1908.
The genus Lytocestus was erected for the cestodes from the siluroid host, Clarias fuscus, from Hongkong. The generic diagnosis was given as: holdfast undifferentiated and not broader than the body, parenchyma muscles in a ring around the testes, and no postovarian yolk glands present.Â To the type species L. adherens Cohn, 1908, several species have been added to date. They are L. filiformis (Woodland, 1923) Fuhrmann and Baer, 1925 [=Caryophyllaeus filiformis Woodland, 1923; Monobothrioides filiformis (Woodland, 1923) Woodland, 1937; L. alestesi Lynsdale, 1956 fide Mackiewicz (1962)] from Mormyrus coschive of river Nile at Khartoum; L. indicus (Moghe, 1925) Woodland, 1926 [=Monobothrioides indicus (Moghe, 1925) according to Woodland (1937)] from C. batrachus in India; L. javanicus (Bovien, 1926) Furtado, 1963 from C. batrachus in Java [= Caryocestus javanicus (Bovien, 1926)]; L. birmanicus Lynsdale, 1956 [=L. alestesi Lynsdale, 1956, accordingÂ to Johri (1959)] from C. batrachus from Rangoon, Burma; L. parvulus Furtado, 1963 from C. batrachus in Java [=Caryocestus javanicus (Bovien, 1926)]; L. birmanicus Lynsdale, 1956[=L. alestesi Lynsdale, 1956, according to Johri (1956)] from C. batrachus from Rangoon, Burma; L. parvulus Futardo, 1963 from C. batrachus in Singapore and Malacca; L. longicollis Rama Devi, 1973 from C. batrachus in India; L. lativitellarium Furtado et Tan, 1973 from C. batrachus Â in Malaysia; L. puylaerti Khalil, 1973 from C. liberiensis in Sierra Leone(Africa);Â L. fossilis Singh, 1975 from H. fossilis from Kathmandu (Nepal); and L. marcuseni Troncy, 1978 from Marcusenius harringtoni Â from Chad basin in Africa. L. fossilis is the only species included in the genus which possesses post-ovarian vitelline follicles. Though its author placed this species under the genus Lytocestus the histological details for ascertaining the family or genus allocation are lacking in its account, thus raising a doubt for including the form with post-ovarian vitelline follicles in the genus. Likewise, another genus Lucknowia Gupta, 1961 that was erected as a new genus distinct form Lytocestus on the basis of the extension of vitelline glands up to the posterior end of the body (Gupta, 1961) was considered synonymous with Lytocestus by Mackiewicz (1994), who opined that the ovarian follicles of Lucknowia were mistaken for postovarian vitelline follicles(Mackiewicz, 1981). All the Lytocestus species, however, appear to be distributed in the Ethiopian and Oriental regions of the zoogeographical realm. Of these, three species, namely, L. indicus, L. longicollis and L. fossilis, are represented from the Indian Sub-continent; besides, L. birmanicus and L. filiformis have also been reported from C. batrachus from the northeastern region of India (Chakravarty and Tandon, 1988).
On comparison with the known Indo-Malaysian species of Lytocestus (L. javanicus, L. parvulus, L. longicollis, L. filiformis and L. lativitellarium), the present form stands close to them in possessing an undifferentiated scolex that tapers anteriad, ovarian lobes extending behind the Mehlisâ€™ gland and uterine coils up to the cirrus sac and in the anterior extent of the testes, i.e., a little posterior to the anterior follicles of vitellaria. In having a short neck and also in the extent of testes and vitellaria, the present form comes close to L. indicus and L. birmanicus. However, it differs from all of them in having a genital atrium (in which open the male and female pores) and spinous eggs. All the species mentioned above have distinctly separated genital apertures and smooth-surfaced eggs.
The present form shares the similar pattern of distribution of vitelline follicles (i.e., concentrated laterally) as in L. lativitellarium but stands apart from the latter species in having smaller body size and shorter neck (about one-fifth to one-sixth of the body length), the vitellarial distribution commencing much anteriorly, and larger spiny eggs.
In view of the above differences, the present form stands out as a species distinct from the known species of Lytocestus and is, therefore, considered a new species and named after the generic name of the host.
Elongated body, undifferentiated scolex, short neck, H-shaped ovary, with arms extending beyond the Mehlisâ€™ gland; confluent male and female apertures opening in shallow genital atrium; spiny eggs.
Named after the generic name of the host.
NEHU/Z - CF/1
Holotype: IV/ERS 286; Paratype: IV/ERS 287; T. S. series: IV/ERS288
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Troncy, P.M. (1978). New parasite records from Chad basin freely water fields. Bulletin IFAN (Ser A). 40(3): 528-552.
Gupta, S.P. (1961) Caryophyllaeids (Cestoda) from fresh water fishes of India. Proceedings of the Helminthological Society of Washington. 28, 38-50.
Mackiewicz, J.S. (1994). Order Caryophyllidea van Benden in Carus, 1863. In Khalil LF., Jones A. and Bray RA. (eds.): Keys to the cestode Parasites of Vertebrates. Cambridge, UK, University Press. pp 21-43.
Chakravarty R. and Tandon V. (1988). On the present status of caryophyllidea with a report on some caryophyllidean infections in the fresh water catfish Clarius batrachus (L.) in North-east India and a record on anomalous form. Indian Journal of Helminthology. 5(1): 37-54.