Species delimitation of eight ascidian (Tunicata) species from the North Eastern Mediterranean

Abstract

Members of the tunicates, a subphylum of marine filter-feeder chordates, inhabit all marine and oceanic habitats from the subtidal to the abyssal. Considered as the closest relatives to the vertebrates, the tunicates are widely used as model organisms for evo-devo, allorecognition, senescence, and whole-body regeneration studies. Yet, species boundaries are poorly understood due to high morphological and genetic plasticity that characterize many tunicates taxa. Here we study taxonomy and the distribution of eight tunicate species (Botrylloides niger Herdman, 1886/ aff. leachii, Botrylloides israeliense Brunetti, 2009, Botrylloides sp., Botrylloides anceps (Herdman, 1891), Botryllus schlosseri (Pallas, 1766), Didemnum perlucidum Monniot F., 1983, Symplegma brakenhielmi (Michaelsen, 1904) and Polyclinum constellatum Savigny, 1816) sampled from six Turkish North Eastern Mediterranean Sea sites and employed the mitochondrial barcoding marker (COI) for evaluating the relationships among geographically restricted and widely spread ascidian species. Species delimitation analysis was conducted using NCBI and the present study sequences. Morphological examinations were first done in the field and then, styelide colonies were cultured in the laboratory and studied using stereo and light microscopes. A putative new Botrylloides species (Botrylloides sp.) from the Antalya region was revealed, with 99% matching on the COI gene from Saudi Arabia, further awaiting for detailed traditional taxonomy.