Brockerhoff, Annette (1993) Parasitological investigations on Portunus pelagicus (Decapoda) in coastal waters of Australia and the Philippines = Parasitologische Untersuchungen an Portunus pelagicus (Decapoda) an Küstengewässern von Australien und den Philippinen. (Diploma thesis), Christian-Albrechts-Universität zu Kiel, Kiel, Germany, 112 pp.

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Abstract

This study reports the symbiont and parasite fauna found in the edible crab Portunus pelagicus (L.) from seven populations located on the north and east coasts of Australia and the Philippines in 1992. P. pelagicus was found to be infected with 23 species including 4 protozoans, 9 helminths, 9 crustaceans and one mollusc. Their geographical distribution, prevalence and intensity are recorded. The impact of parasites on the crab fishery and special aspects of parasite-host-relationship are discussed and as far as possible evaluated for several species. The symbiont and parasite communities of P. pelagicus were similar in the tropical and subtropical areas investigated. The gooseneck barnacle 0. neptuni and the egg predators Carcinonemertes mitsukurii and Choniosphaera indica were recorded in all sampling locations. The acorn bamacle Chelonibia patula , the gooseneck bamacles 0. warwickii and 0. tridens occured in six, and 0. angulata, 0. bullata, Operculariella sp. and the metacestode of Polypocephalus sp. nov. in five sampling locations. The rhizocephala Sacculina granifera was detected on the north and east coasts of Australia. The protozoan blood parasites Ameson sp. and Hematodinium sp. and a planoceroid turbellarian were found only in Queensland. A single bopyrid of the genus Allokepon was found in the Philippines. The metacercaria of Melogonimus rhodanometra (Ptychogonimidae) was found in Queensland, Australia and is described. The name was given according to the adult worm recently found and described as a new species (Bray, Brockerhoff & Cribb, submitted). The metacestode of Polypocephalus sp. nov. (Lecanicephalidae) was found in Australia and the Philippines and is described as a new species. Electron microscopical investigations were done on morphological aspects of the scolex of Polypocephalus sp. nov. Ultrastructural observations of the tegument of the scolex reveals posteriorly directed, triangular hooks. The tentacle-tegument bears an unusually large number of electron-dense granules vesicles. The functions of this vesicles is not known. lt is possible,
however, that they aid adult worms to attach to their definitive hosts, either by producing
enzymes that degrade the intestinal mucosa of the host, or by producing a cement that binds the
worm to the mucosa. This is the first report of flame cells in cestode tentacles. Since the worm
has !arge numbers of tentacles (> 300), they can increase the excretory surface of the worm
enormously. Tue possible functions of the tentacles are discussed.

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