Meeting Abstract

P1.128  Jan. 4  Evolutionary relationships among sea anemones (Cnidaria: Actiniaria: Hormathiidae) symbiotic with hermit crabs (Arthropoda: Crustacea: Paguroidea) GUSM�O, L.C.; Ohio State University, Columbus, Ohio Gusmao.1@osu.edu

Most sea anemones that engage in symbiosis with hermit crabs belong to family Hormathiidae. The family Horrmathiidae is a complex and diverse group distributed globally and dominating the deep sea and the largest family in the Acontiaria – one major lineage of sea anemones. It includes nearly 16 genera, 3 of which are associated with hermit crabs and another to gastropods. The degree of obligation among these symbionts varies from casual to strict associations. Members of Adamsia, which form chitinous carcinoecium, present the highest degree of obligation, whereas Paracalliactis includes members that may secrete either a carcinoecium or a small plate, and thus exhibits intermediate levels of obligation. Members of Calliactis are the least obligated, including species that carry on a life independent of hermit crabs. Members of Allantactis, in the other hand, are commonly found living associated to gastropods. The diversity of interactions raises critical questions about the emergence and evolution of these symbioses. Competiting hypotheses concerning the emergence of these associations include the crab-driven hypothesis, in which species become associated via activity of the crabs transfering anemones to its shells or the shell response hypothesis, in which anemones would attach themselves to shells according to a shell factor and independently of the crab�s acitivity. Sequence data from 2 mitochondrial genes (12S and 16S) and two nuclear genes (18S and 28S) is used to investigate the evolutionary implications of the symbiotic life in terms of morphological and biological transformations, relationships among closely related families and monophyly of hermit crab associates.