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30.11.2023

Sara Kast BSc

Austrolethops wardi (Teleostei: Gobiidae) – does phylogenetic conservatism obscure trophic ecology?

Advisor:Harald Ahnelt

Master's Defensio - Thursday, November 30th 2023
SR 5.1, UBB
Djerassiplatz 1, 1030 Vienna

Abstract

The morphology of the trophic structures, oral and pharyngeal jaw elements, dentition and gill ray spines of the first gill arch of four Indo-Pacific sympatric goby species with different trophic ecology were investigated by micro-CT scans. Within the Gobiidae, the phylogenetic position of Cryptocentrus cinctusAmblygobius phalaena and Valenciennea sexguttata is known, but that of Austrolethops wardi is unresolved. The trophic level of C. cinctus (carnivorous), A. phalaena and V. sexguttata (both omnivorous) is reflected in the morphology of the intestinal tract, whereas the herbivory of A. wardi is not. Although A. wardi feeds almost exclusively on seagrass, its intestinal tract is similar to that of the carnivorous species. There are also distinct morphological similarities in the trophic skeletal structures between the herbivorous A. wardi and the carnivorous C. cinctus: the oral jaws show dense dentition with a similar number of tooth rows in the upper and lower jaws, the pharyngeal jaws are more massive and robust than in the two omnivores and the pharyngeal teeth are shorter and stronger. Austrolethops wardi differs from C. cinctus both in the shape of the premaxilla, which is long and narrow, and in the absence of hooked pharyngeal teeth. This could be an adaptation to a herbivorous feeding behavior. From the similarities between A. wardi and C. cinctus it can be concluded that the trophic structures in A. wardi are phylogenetically conserved and that the ancestor of this species was carnivorous.