RICE, M.E.; SCHULZE, A.; Smithsonian Marine Station, Ft. Pierce, FL; Smithsonian Marine Station, Ft. Pierce, FL: Molecular and morphological species identification of pelagic sipunculan larvae

Planktotrophic sipunculan pelagosphera larvae possess a pronounced metatroch and distinctive head morphology with at least one pair of pigmented eyes and a lower lip. Many morphotypes of pelagospheras can be distinguished by size, color, ciliation patterns, structure of the body wall, absence/presence of a terminal organ and head morphology. Despite distinct morphologies, species identification is usually not possible. Here we present the results of two methods for species identification of sipunculan larval morphotypes: 1. Some larvae were raised to juveniles or adults in the lab and 2. For ten larval types, we sequenced the gene regions from the nuclear genes histone H3 and 18S ribosomal RNA as well as the mitochondrial cytochrome c oxidase subunit I. We compared the sequences to a database of sequences from adult sipunculans. Using the sequence data, larvae of the following species could unambiguously be identified: Apionsoma misakianum, Xenosiphon branchiatus, Siphonosoma cumanense and Aspidosiphon laevis. Other larval types could only be identified to genus or family, or the three genes gave conflicting results. In addition, we confirm the presence of two cryptic species of Apionsoma misakianum from the Caribbean and the Florida coast, respectively, as previously suggested by allozyme data. The species are indistinguishable in adult morphology but distinct in larval morphology and genetically separated. All larval types are documented by light microscopy and/or scanning electron microscopy as a reference for future studies in larval ecology.