Meeting Abstract
Scale worms (Aphroditiformia) are one of the most diverse families of annelids (<1200) found in all marine habitats including many extremes such as anchialine caves, the interstitial environment, whale falls, and hydrothermal vents. The wide range of habitat colonization reflects a complex evolutionary history, yielding a vast array of adaptations and life history traits. Here we present the most diverse phylogeny of scale worms, including several undersampled lineages using four molecular markers and morphological data with both character and habitat reconstructions. Our dataset includes 50 newly sequenced taxa analyzed using probabilistic methods; including 8 anchialine cave endemics and 17 exclusively interstitial from throughout the world. Two independent interstitial colonizations events are traced within the Sigalionidae-Pholoididae clade, i) origin of the clade Pisione-Pisionidens, characterized by an elongation of the body and loss of elytra; ii) and the clade Laubierpholoe, characterized by a reduction in the number of segments and elytra brooding. Amongst the Polynoidae, a single colonization event to anchialine caves is represented by the anfiatlantic Gesiella and Pelagomacellicephala lineages. This clade exhibits stygobitic features, including reduction of eyes and pigmentation, elongation of sensory appendages, and evolution of pelagic swimming behavior. Our analysis also supports a relationship between cave Macellicephalinae and Gesiellinae and deep-sea clades. Adaptations amongst Aphroditiformia, especially the elytra morphology related to these colonization events is briefly presented, combining SEM, CLSM and observations of live specimens.
