Bennettella ceticola (Nelson ex Bennett) Holmes on the skin of Franciscana dolphin ( Pontoporia blainvillei ) of the Argentinean Sea: an emendation of the generic description

FAZIO, ANA; FERRARIO, MARTHA E.; BORDINO, PABLO; FERRARIO, MARTHA E.; BORDINO, PABLO; CEFARELLI, ADRIÁN O.; ROMERO, OSCAR E.; CEFARELLI, ADRIÁN O.; ROMERO, OSCAR E.; FAZIO, ANA

DIATOM RESEARCH

BIOPRESS LIMITED

Año: 2019 vol. 33 p. 485 - 497

0269-249X

The presence of epizoic diatoms on the skin of a variety of large marine vertebrates, such as whales and dolphins, has been often reportedin the scientific literature. The first observations of an algal growth over on the skin of cetaceans were probably made around 1920. Laterstudies showed the presence of a new species, Cocconeis ceticola, on skin samples. Morphological features of this species led to thetransference of C. ceticola, together with related forms, to the new genus Bennettella Holmes.Here, we report the occurrence of a diatom film of Bennettella ceticola on the skin of the Franciscana dolphin (Pontoporia blainvillei),obtained from bycatch in fishermen?s gillnets at Samborombon Bay, Argentina, in April 2005. For comparison the holotype of B. ceticola,deposited in the Natural History Museum (London, U.K.) dated 1920 and labelled as Cocconeis ceticola was examined. Detailed analysisof the fine structure of B. ceticola shows that it mostly matches the original description. However, the external raphe ending is notbifurcated (as originally described), and has only one simple, parallel sided slit and polar fissures hidden by a triangular flange. Thetriangular flange is the main diagnostic feature distinguishing Bennettella from Epipellis Holmes and Cocconeis Ehrenberg, allowing usto propose an emended description of Bennettella. The taxonomic affinities of B. ceticola with related genera, such as Cocconeis andEpipellis, are discussed. The present study constitutes the first report of B. ceticola as an epizoic diatom of a cetacean species in watersof the Argentinean Sea.