Studies on the digenetic trematodes of Australian freshwater fish

Abstract

This thesis has been produced with the aim of contributing to the knowledge of the adult digenetic trematodes of Australian freshwater fish. There are about 190 species of freshwater fish in Australia but up to the p resent only about twenty species of digenetic trematodes have been recorded from them. In this study freshwater fish from various parts of Queensland were examined for trematodes and a collection of trematodes from the Australian Helminthological Collection was examined. Eight new species are described, one New Zealand species is recorded from Australia, and four presently undescribed species are recorded. Two new genera and species are described for the Cryptogonimidae, the diagnosis of the Neochasminae is emended, and Parspina is excluded from the Cryptogonimidae. A third probable new genus of cryptogonimid is recorded and Telogaster opisthorchis, originally described from New Zealand, is recorded from Australia. A new species of Opecoelus is described for the Opecoelidae and a second new species is recorded. Opegaster is made a synonym of Opecoelus. A new species of Phyllodistomum is described and a second new species recorded for the Gorgoderidae. As well a new genus is proposed for part of the Phyllodistomum group and two new species are described for it. A new genus and species are described for the Derogenidae. A new species of Stegodexamene is described for the Lepocreadiidae.nA new species of Haplorchoides is recorded for the Heterophydae.Life-cycle studies have been published on only five species of trematodes from Australian freshwater fish. In the present study lifecycle data are presented for eight species. One of the new genera of Cryptogonimidae uses the hydrobiid prosobranch Posticobia brazieri as first intermediate host and eleotrid fish as second intermediate hosts. This life-cycle is described with particular emphasis on the development of the mother sporocyst. Cryptogonimid cercariae are characterized nas a group distinct from other opist horchioid cercariae. On the basis of this and other evidence it is suggested that Pseudexorchis be returned to the Heterophyidae. The second new genus of cryptogonimid is presumed to use eleotrid fish as second intermediate hosts and it is postulated that the cercariae lack eye-spots as the adults have no residual eye-spot pigment. n