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Monogenea are almost exclusively ectoparasites of aquatic vertebrates. According to Baer (1951) at least 95% of the genera have been reported from fishes, primarily the elasmobranchs. Some monogeneans also occur on the gills, or in the mouth and urinary bladder of amphibians and reptiles and even one species has been reported from the eye of the hippopotamus. The monogeneans are morphologically similar to rhabdocoel turbellarians of the family Graffillidae. They are small worms with posterior portion of the body modified to form a haptor, a disc-like structure, with hooks or suckers or both and is a powerful adhesive organ. The anterior end bears the mouth and pharynx. The intestine may be saccate or bifid and is often branched. Excretory system is duplicate with anterior dorsolateral pore.
The worms are hermaphroditic with a single ovary and one or many testes. Eggs bear long filaments. Life cycle is simple and development is direct. The larva is ciliated and has a brief free-swimming period before it attaches to the host
Class Monogenca is divided into two subclasses (1) Monopisthocotylea with two orders and (2) Polyopisthocotylea with two orders. Sproston (1946) had listed 679 species spread over 130 genera. The number has definitely increased two fold by now.
The earliest reference on Indian Monogenetic trematode appears to be that of Bell (1891), who described a new species, Tristoma hisliophori now known as Capsala laevis (Verrill, 1874)from Ilistiophorus brevirostris caught at Madras. Von Linstow (1906) described another new species, Tristomum megacotyle parasitic on the body of sword fish, Istiophorus fished off Sri Lanka coast. According to Chauhan (1952) this collection was composite and consisted of Capsala megacotyle and Capsala avalis. Luhe (1906) reported a new species Epibdella macrocalpa (= Benedenia macrocalpa) from the skin of Rhinoplesa javerica caught in Sri Lanka. Stewart (1914) described Polystovorum kachugae from the urinary bladder of Kachuga lineata from freshwaters of Lucknow.
This species is now known as Polyslomoides kachugae. Thapar (1929) reported the excretory system of Discocotyle sagittalum at Lucknow. After Stewart it took more than two decade for another work to appear when Price (1938) described Dactylogyrus moorthyi on a collection from Puntius puckelli and P. ticto made by Moorthy at Chitaldrug, Karnataka. Dayal (1941) reported Diplozoon indicum from a freshwater fish Puntius sarana at Lucknow. Chauhan (1945) made large collection from marine fishes of Bombay coast and described two new genera, viz. Bilalerocotyle and Pricea and eight new species. Bhalerao (1945) described Loimos secundus infecting the gills of Indian dog fish, Scoliodon sorrakowah from Rangoon. Thapar (1948) erected a new genus and species Paradactylogyrusfaflaius from Calla calla at Lucknow. Kaw (1950) reported a new species of Diplozoon kashmirensis infecting the gill of Schizothrax sp. in Dal Lake, Srinagar and also erected a new genus Eupolysloma with E. rajai as its type collected from the urinary bladder of a frog Rana sp. at Pinch [Poonch?], Kashmir.
Subhpradha (1951) described a new genus and species Vallisiopsis cantorta and another new species Gastrocotyle indica from marine fishes at Madras. Ramalingam (1952) added six new species to genus Pricea collected from Gymbium guttatum at Madras. Chauhan (1950, 1952) described three new species, Mazocraes orientalis Mazocraeoides prashadi from marine fishes collected at Puri and Capsala gour; from Thynnus thunnina taken at Bombay. Chauhan (1953) in his monograph on the Indian Monogenea compiled the description of 30 species described till then besides discussing the classification and phylogeny of the group and a host-parasite list of Indian species. Tripathi (1954) described two new genera, viz. Bicotyle and Megamicrocotyle and six new species. Tripathi (1957) published a monographic paper in which he added 68 new species, including 13 new genera and three new families to the Monogenea fauna of India. Jain (1958-1961) added a number of new species and new genera from freshwater fishes from Lucknow. Unnithan (1957, 1961, 1964) studied the monogeneans of marine fishes of south western coasts and added a number of new species besides discussing the taxonomy.
Silas (1967) gave a list of monogenous of Scombroid fishes. Gupta and Khullar (1968) reported a new species. Heteraxinoid pseudosciaenai besides redescribing a number of known species from marine fishes off Bombay and Calicut. Karyakarte (1967-72) worked on the monogenea of Marathwada fishes. Kulkarni (1969) described Monogenea from freshwater fishes of Hyderabad. Gussev (1974) in a monographic study discussed the systematics of Indian Monogenea described till then and gave an analysis of the world fauna and evolution of the group.
Agarwal and Kumar (1980) described a new species parasitic on the gill of Bagarius bagarius at Varanasi. Gupta, and Sharma (1981), Gupta, (1983) added new species to the genus Bifurcohaptor. Srivastava, (1984) gave an analysis of the Monogenea infecting estuarine fishes. Agrawal, and Singh (1980-1990) in a series of papers worked out the Monogenea of freshwater fishes of Lucknow. Rao (1975) described a new species Polystomoides sinhai from the urinary bladder of Kachuga tectum tentoria caught from Godavari river in Nizamabad district. Khocha (1971-78) worked on monogeneous marine fishes of Arabian Sea.
Estimation of Taxa
Families Genera Species 28 110 295 There is a big lacuna with regard to Monogenea of marine fish. The freshwater fishes also deserve more attention with regard to monogenean infection.
M. Hafeezullah, C. B. Srivastava, R. K. Ghosh, S. B. Bhattacharya all of Zoological Survey of India, 'M' Block, New Alipur, Calcutta -700 053.
\ B. S. Chauhan, 220, Civil Lines, Narsinghpur
Y. R. Tripa~i -Lucknow
K. Ramalingam, Annamalai University, Annanamalai Nagar.
K. 'C. Pandey, Meerut University, Meerut
N. Agrawal, Lucknow University, Lucknow
R. V. Unithan, Indian InsU. Oceanography, Goa.
H. S. Singh, Meerut University, Meerut.
T. Kulkami, Osmania University, Hyderabad.
A. V. Gussev, Zoological Institute, Academy of Science, USSR, Leningard
W. S. Hargis, Virginea Fisheries Lab. Gloucester Point, Virginia, U.S.A. Lamothe, A. R. Laboratorio de Helminthologia Institute de Biologia, U.N.A.lvl., Mexico. Ian Whittington, Deptt. of Parasitology University of queens Land, St. Lucia, 4067 Australia.
J. L. Lewellyn. Depu. of Zoology &Comparative Physiology, University of Birmingham England.
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Dawes, B. 1946. The Trematoda. Cambridge Univ. Press. London.
Yamaguti, S. 1963. Systemallelminthum. Vol. IV. Monogenea. Interscience Publ. N. Y.
Unnithan, R. V. (1957). Functional morphology of a new fauna of Monogenea of fishes from Trivandrum and environs I. Aximidae fam. nov. Bull. Cent. Res. Just, Ulli\'. Kerala 5, 27-122.
Unnithan, R. V. (1961). On the functional morphology of a new fauna of Monogenea of fishes from Trivandrum and environs. Part 3, Heleromicrocotylidae (Microcotyloidea) Indian J. Helminth. 13, 112- 145.
Unnithan, R. V. (1964). On Dawesi indica gen. et sp. n. a monogenetic trematode from the gills of the marine fish Scomberomoms gll1tall!S (Bloch & Schn.) of Indian Waters. Ann. Mag. l1at. His!., Ser. 13,7,463-472.
Unnithan, R. V. (1964). On five new species of monogenetic trematodes parasitic on the gills of marine fishes from the south-west coast of India. Treubia 26, 159- 179.
Unnithan, R . V. (1964). Four new polyonchoineans (Monogenoidae) parasitic on gills of marine fishes from the Indian seas. J, Paras;t. 50, 214-247.
Unnithan, R. V. (1965). On a new monogenetic trematode Homostomo chura gen, et sp. nov. from the marine fish EuthYllnus ajJinis (Cantor) with a note on the family Hexo· stomatidae, (Price, 1936). Trellbia 26, 329- 336.
Unnithan, R. V. (1966). On the functional morphology of a new fauna of Monogenoidea of fishes from Trivandrum and environs Part V. Gephyocolylidae fam. nov. Treubia 21, 53-62.
Unnithan, R. V. (1966). On four new diclodophorids (Monogenoidea) parasitic on the gills of marine fishes from the south·west coast of India. Pacific Sci. 20, 79-90.
Unnithan R. V. (1971). On the functional morphology of a new fauna of monogenoidea of fishes from Trivandrum and environs. Microcolyfidae sensllstriclo and its repatriation into subsidiary taxa. Amer. MidI. Nat. 85, 365- 398.
Unnithan, R. V. (1972). A new monogenetic trematode Sallricoryle sprostoni gen. et sp. n. on the gills of the lizard fish Saurida IIImbii (Bloch) from the Arabian Sea. J. Bombay nat. Hist Soc. 69,220-225.
This page has been edited by Divya Grace Dilip, Assistant Professor, Department of Zoology, All Saints' College, Trivandrum.