Systematics of Corbulidae supported by anatomical and conchological studies remains confused and controversial because of the considerable phenotypic plasticity of their shells. Ultrastructural spermatozoan study and molecular analyses have been performed to contribute valuable information, which could be used in taxonomy. Electron microscopy was used to analyse sperm cells from specimens of Caryocorbula (Gardner, 1926) exhibiting shell differences. The spermatozoon was of the aquasperm type, showing short acrosome, barrel-shaped nucleus, midpiece composed of four spherical mitochondria and simple flagellum. In addition, about 860 base pairs of mitochondrial large ribosomal subunit (16S rRNA) were sequenced from each individual. The consistent similarity shared by spermatozoa and DNA sequences from all studied specimens indicated that they belonged to one coherent unit, Caryocorbula caribaea (d'Orbigny, 1853), despite the extraordinary plasticity exhibited by their shells.

a new combination to S. obliquus does not occur in Brazilian waters. Therefore, one of these Brazilian solenids remains without a formal description probably being a putative new species. Some species of this family have a high commercial value in several Asian and European countries. In Japan and China, particularly, these bivalves are appreciated for their nutritional value as in the case of Solen gordonis Yokohama, 1920, which is collected by inhabitants for food and Solen