Transcriptome Sequencing of Two Species of Ribbon Worms (Nemertea) and Characterization of Ribbon Worm Toxin Genes

Nemertean worms or “ribbon worms” are a phylum of invertebrate animals among whose characteristics are the presence of specialized but largely unstudied toxins used both in defense and predation. We obtained transcriptome data for two nemertean worm species, Carcinonemertes epialti (Carcinonemertidae) and Dushia atra (Lineidae), to investigate the evolutionary histories of these taxa as well as identify and characterize previously identified nemertean toxin genes (Whelan et al. 2015). Species of Carcinonemertes are of particular interest because they are obligate symbionts of crabs and eat their developing embryos; therefore, probably with no need for either type of toxin. Is that expectation borne out by transcriptome data? Phylogeny within Nemertea has been well characterized by two multigene studies (Thollesson & Norenburg 2003, Andrade et al. 2014a), whose broad consensus results were recently supported by a transcriptomics study (Andrade et al. 2014b). Data from that last study are combined with our new nemertean transcriptome data and reanalyzed, to test the placement of these two taxa inferred by the previous multigene studies.