Larval morphology of Megaporus Brinck, 1943 (Coleoptera: Dytiscidae): descriptions of M. hamatus (Clark, 1862) and M. gardnerii (Clark, 1862) and phylogenetic considerations

Abstract

The larvae of the Australian endemic species Megaporus gardnerii (Clark, 1862) and M. hamatus (Clark, 1862) are described and illustrated for the first time, with detailed morphometric and chaetotaxic analyses of the cephalic capsule, head appendages, legs, last abdominal segment, and urogomphi. We explore implications for understanding the evolution of larval morphological traits amongst selected Sternopriscina genera. A parsimony analysis based on 84 larval characteristics of seven species in five genera was conducted using the program TNT. Larvae of Megaporus Brinck are characterized by the primary seta AB3 articulated distad of seta AB2, a very elongate siphon, and predominantly elongate and hair-like secondary setae on the urogomphi. Megaporus is postulated to be closely related phylogenetically to Chostonectes Sharp in the context of this study, which reinforces previous hypotheses based on adult and molecular data sets. These results provide a phylogenetic framework for future studies of the larvae of the Sternopriscina.