Speciatie in het parasietengenus Gyrodactylus (Monogenea, Plathyhelminthes) op grondels van het genus Pomatoschistus (Gobiidae, Teleostei)
Audenaert, V. (2001). Speciatie in het parasietengenus Gyrodactylus (Monogenea, Plathyhelminthes) op grondels van het genus Pomatoschistus (Gobiidae, Teleostei). MSc Thesis. KUL: Leuven. 102, XVI pages annexes pp.
In this study attention has been paid to morphological and genetic variation between some Gyrodactylid species (Monogenea, Plathyhelminthes) parasitising the fins, skin and gills of Pomatoschistus gobies (Gobiidae, Teleostei). Gobies are recorded from the north-eastern Atlantic and Mediterranean coasts and thus have a large expansion area that reflects their mobility. There are 11 species of gobies, of whom some occur sympatricaly in the Mediterannean and the North Sea and share the same parasitic fauna. The ectoparasitic genus Gyrodactylus of which over 400 species are known, has a complex taxonomy. A microscopic morphometric analysis was carried out on the opistophoral hard parts of two recently speciated gyrodactylids from two different host species and various locations. The results showed important interspecific variation to which especially the length of the marginal hooks contributed. There were some intraspecific host dependant and geographic differences which differentiated Gyrodactylus cf. rugiensis from the Mediterannean and the North Sea. We developed a method for the easy and reliable identification of some gyrodactylids based upon only the length of the marginal hook. However the importance of molecular data in defining species boundaries was also shown. Based upon the morphological and genetic data a species description was made of Gyrodactylus rugiensis and Gyrodactylus cf. rugiensis which were thought to be a single species earlier on. A putative new species was discovered on Gobiusculus flavescens, a goby which is closely related to the gobies of the Pomatoschistus genus. The morphometrical as well as the genetic data suggest a gyrodactylid very similar to Gyrodactylus cf. rugiensis. Finally a phylogeny was inferred from 5 gyrodactylid species that showed incongruence with the phylogeny of their hosts. This could be partially explained by the occurrence of host switching and gene flow in areas where host species live sympatricaly. Phylogenetic host specificity as well as ecological aspects such as host switching and gene flow play an important role in the host-parasite associations under study.
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