136.4 Monday, Jan. 7 Biodiversity of nemertean larval forms in NE Pacific MASLAKOVA, SA*; VON DASSOW, G; HIEBERT, LS; HIEBERT, TH; Oregon Institute of Marine Biology, Univ. of Oregon email@example.com
Planktonic larvae of many marine invertebrates look nothing like their benthic adults, and the problem of matching the two life-history stages is as old as the studies of plankton. Nemertean larvae are commonly found in plankton samples. They are diverse and distinct, but at present can only be identified to class or family level at best. This is because the development of most species is unknown. Our efforts over the past four years to match planktonic nemertean larvae from Coos Bay, Oregon to morphologically identifiable adults using DNA sequence data revealed a surprising amount of undescribed species-level diversity in a region where nemertean fauna is thought to be well characterized. We found many species new to science, and detected species previously known only from the other side of the Pacific Ocean. We identified planktonic larvae of several hoplonemerteans, including Carcinonemertes errans, an egg predator and parasite of commercially important crab species. Contrary to expectations, these hoplonemerteans appear to have long-lived pelagic larvae that feed and grow in the plankton, which is likely to have consequences for larval dispersal and population connectivity. We solved a long-standing mystery of the identity of an unusual larva called pilidium recurvatum, and discovered a new trochophore-like lecithotrophic pilidial larval type; both of these findings have implications for the evolution of larval form. A particularly important emerging insight from this study is that while nemertean larvae often have species-specific morphology, they can also be grouped into morphotypes that characterize clades of closely related species. This means that larval characters may provide unique synapomorphies to help define phylogenetic clades in this morphology-poor phylum.