The functional anatomy of the anterior end of Skrjabinoptera goldmanae from Australian agamid lizards

Abstract

AbstractFour muscle groups are responsible for the eversion and retraction of the apical denticles and enlarged pseudolabia in Skrjabinoptera goldmanae (Nematoda: Physalopteridae), which occurs in the lizards Chlamydosaurus kingii, Pogona spp. and Varanus gouldii in Australia. These muscles enable the nematode to bury its anterior portion in the gastric submucosa of its hosts. They comprise three sets which are derived from the somatic musculature and are inserted in the oesophagus and associated organs, and a fourth set of muscles which appears to be derived from the muscular oesophagus itself. These accessory muscle groups are described and illustrated, and from this their mode of action in everting and retracting the pseudolabia is derived. Possible selection pressures which led to their evolution are reviewed.