The end of pelagic Stauromedusae? A century of taxonomic confusion.

RODRIGUEZ C.; MARQUES A. C; STAMPAR S.; MORANDINI A.; CHRISTIANSEN E.; GENZANO G. N.; MIANZAN H.

MAr del Plata

Simposio; 3rd Jellyfish Blooms Symposium; 2010

INIDEP

The end of pelagic Stauromedusae? A century of taxonomic confusion Carolina S. Rodriguez1, 2, Antonio C. Marques3, Sérgio N. Stampar3, André C. Morandini3, Ernesto Christiansen4, Gabriel N. Genzano1, 2, Hermes W. Mianzan2, 4. 1 Estación Costera Nágera, FCEyN - UNMdP, Funes 3250, (7600) Mar del Plata, Argentina 2 Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina 3 Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, Brazil. 4 Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP), PO Box 175, (7600) Mar del Plata, Argentina The taxonomy based on the study of fixed individuals always demand careful analyses because minor interpretative mistakes could cause the identification of different phases of a life cycle as separate species, leading to taxonomical confusion and false conclusions. Therefore, the goal of this study was to reinterpret the pelagic Stauromedusae family Tesseridae, accessing the taxonomic position of Tessera gemmaria Goy, 1979, a stauromedusae considered as incertae sedis for a long time. This pelagic taxon constitutes an exception to the Staurozoa, a sessile group known as stalked jellyfish. Eighteen specimens identified as the same morphotype of T. gemmaria were collected between Southeastern Brazil (Rio de Janeiro State) and Northern coast of Argentina. Using histological preparations to analyze and compare these specimens with previous descriptions we conclude that T. gemmaria is actually a larva of the anthozoan group Ceriantharia belonging to the genus Cerianthula. The morpho-histological analysis revealed several anatomical structures that support our conclusion, such as: hollow tentacles with terminal buttons of cnidocysts; actinopharynx with one siphonoglyph and 4-5 coupled mesenteries; and aboral cnidocyst button with spyrocysts (a cnida type exclusive of the Anthozoa). Concluding, we propose that the staurozoan planktonic family Tesseridae, established by Haeckel in 1880 for free-living stauromedusae, is actually a misinterpretation of different larval stages of tube anemones (order Ceriantharia).