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Development and maturation of Philonema species (Nematoda: Philometridae) in salomid hosts with different life histories Bashirullah, Abul Kashem Mohammed

Abstract

This study was undertaken to determine the identity of Philonema oncorhynchi from anadromous sockeye and Philonema agubernaculum from non-anadromous trout, and also to test the hypothesis that the worm in salmon is dependent on hormonal stimulus from the host for synchronization of reproduction. On the basis of differences found in life cycles, cross infection and starch gel electrophoresis, P. oncorhynchi and P. agubernaculum are considered to be different species. The hypothesis was tested experimentally, using salmon pituitary extracts and synthetic stilbestrol. Pituitary extracts accelerated the production of larvae in the uterus, of the worm and stilbestrol inhibited the gonadal development of the fish, but had no apparent effect on the worms. The hypothesis was further supported by the results of transplantation of adult but non-larvigerous worms from maturing sockeye into immature trout. Larval development failed to take place in recipient hosts. As well, larvigerous worms were collected only from sexually mature fish, whether 3, 4 or 5 years old. Rapid development of the worm paralleled the rapid gonadal development of the fish during the last 6 months of the fish's life. Sexually immature sockeye had only immature worms.

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