Studies on the Helminth parasites of marine fishes, with emphasis on the Zoogonidae (Platyhelminthes:Digenea)

Bray, Rodney Alan (1985). Studies on the Helminth parasites of marine fishes, with emphasis on the Zoogonidae (Platyhelminthes:Digenea). PhD thesis The Open University.



The family Zoogonidae (Platyhelminthes:Digenea) is studied to elucidate its taxonomy. The data were accumulated by extensive collecting, by the examination of specimens in the collection of the British Museum (Natural History) and other museums and from the scientific literature. In Chapter one numerical and cladistic techniques are used to manipulate the data and an explicit overall classification is produced. Two subfamilies, the Zoogoninae and the L epidophyllinae are recognized. The Zoogoninae contains 9 genera and 27 species and the Lepidophyllinae 12 genera and 50 species. The number of recognized genera is reduced from 30 to 21 and species from 127- to 77. Original definitions are given for all supraspecific taxa and original keys are produced to most recognized species. The value of the various techniques used is assessed and manual (as opposed to computer-processed numerical) cladistics is considered the most useful m odern technique for handling the type of data presented by these digeneans. Some aspects of host-and site-specificity and zoogeography are discussed and a host-parasite list (including over 330 fish species) is given. Chapter two consists of a detailed study of the zoogonids from the NE Atlantic region based on material of all the species recognized. Seventeen species are found, 7 zoogonines and 10 lepidophyllines. Four new lepidophyllines, three from deep-sea fishes, are described. The zoogonid fauna of the NE Atlantic is found to be dominated by boreal species with a few southern forms reaching into the southern (Lusitanian) fringes of the region. Chapter three is an examination of the marine catfish Anarhichas lupus as a host of zoogonids and other helminths. The morphology of the gastro-intestinal tract and some associated organs and some of their physico-chemical characteristics are described. The most unusual feature of the gastro-intestinal physiology discovered is the reduced level of acid production in the stomach. Helminths found throughout the gastro-intestinal tract, the biliary system and the urinary bladder are found to have fairly restricted distributions and those found in regions other than the gastro-intestinal tract appear to be restricted to specific organs. The stomach apparently lacks true parasitic-helminths. Evidence of the degree of site-specificity exhibited by the zoogonids and other helminths of Anarhichas lupus is given.

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