Gross morphology and cnidae of edwardsiella anemones and larvae (Anthozoa, Edwardsiidae) from the Swedish West Coast

Abstract

AbstractThe American ctenophore Mnemiopsis leidyi, recently found in Skagerrak off the Swedish west coast, carried parasitic anemone larvae identified as Edwardsiella sp. In the Western Atlantic Ocean, M. leidyi are commonly infected by larvae of American Edwardsiella lineata anemones. It was questioned whether the parasitic larvae came across the Atlantic with the invasive ctenophore, or whether they belonged to the native E. carnea anemones. However, recent molecular investigations identified E. carnea and E. lineata as different species and the Swedish larvae from M. leidyi as E. carnea. Present morphological investigation supports the distinction of E. carnea anemones from E. lineata by a changeable rounded to flattened physa without rugae and by white pigmentation on basal outer tentacles. One Swedish larva developed into a juvenile with this characteristic column differentiation, identifying our larva as E. carnea and confirming its ability to produce parasitic larvae. Cnidome descriptions of E. carnea anemones and larvae reveal three similar cnidae in E. carnea and E. lineata anemones and larvae, and cnidae specific to either anemone or larval stages. Cnidome characteristics support our parasitic larvae as an Edwardsiella member, but further comparable studies of E. lineata cnidomes are warranted for evaluating their taxonomic significance.