REVISION OF DIPLECTANID MONOGENEANS (MONOPISTHOCOTYLEA, DIPLECTANIDAE) IN SILLAGINID FISHES, WITH A DESCRIPTION OF A NEW SPECIES OF MONOPLECTANUM

Five species of diplectanids are described or redescribed on the basis of sclerotised parts, from a survey of 26 species of Sillaginidae in the Indo-west Pacific. Diplectanum sillagonum Tripathi is widespread, and is recorded on Sillago sihama from tropical Australia north to Hon g Kong and west to India, as well as on S. vincenti (in India) and S. attenuata (Persian Gulf). Diplectanum blairense Gupta & Khanna infects S. sihama and S. indica and is sympatric with D. sillagonum over some of its range (Hong Kong to India and south to Ball). Diplectanum flag ritubus Nagibina is synonymised with D. blairense. Diplectanum puriens e Tripathi is redescribed from S. chondropus in western Thailand, but was not found on specimens of its type host, Sillaginopsis panijus fro m the Bay of Bengal. Monoplectanum youngi sp. n. is described from Sil lago analis, S. ciliata, S. sihama, S. parvisquamis, S. lutea and S. a ltenuata and is more widespread than D. sillagonum, extending into sub tropical waters in Australia. Monoplectanum australe Young infects S. maculata and S. burrus, and appears to be endemic to Australia. The di agnosis of Monoplectanum, until now monotypic, is emended; the genus i s unlikely to contain more new species on sillaginid fishes, and its t wo species probably share a common ancestor with D. blairense. Parasit ological evidence favours a close relationship between Sillaginidae an d Sciaenidae. (C) 1997 The Norwegian Academy of Science and Letters.