Abstract

Dorid nudibranchs (Gastropoda: Nudipleura) are a key taxon for studying the evolution and interaction of chemical defense, color patterns and feeding specialization, but we lack a robust phylogeny for hypothesis testing. To provide new morphological characters, we investigated the extensive interior spicule networks of several dorid taxa. We compared traditional staining methods vs micro computed tomography (?CT) of 31 specimens representing 10 species of Aldisa, Cadlina and Onchidoris. We found that ?CT offered a non-destructive view of sufficient resolution to study the gross morphology of networks, although images of fine structures were too grainy to allow robust comparisons. Network form did not vary within species and was consistent within genera. The three genera varied in several obvious characters, such as presence of a pleural sinus channel, large dorsal spicules, and multispicular tracts, as well as in relative size, shape and orientation of spicules. These characters, combined with those from the literature, supported recent molecular phylogenies that group Cadlina with Aldisa, and that question the monophyly of the Cryptobranchia. This suggests that these network forms will prove a fruitful source of phylogenetic characters with at least genus-level resolution.