Didemnum tetrahedrum sp. nov., a new Didemnum (Tunicata: Ascidiacea) species from south-eastern Brazil.

A new species of Didemnum was discovered during a recent biodiversity survey of Praia da Baleia, São Sebastião, São Paulo State, Brazil. This species has a unique and peculiar type of spicule composed by four calcareous spheroids grouped together to form a tetrahedral structure. In other aspects, the new species is similar to certain other whitish tropical Atlantic American didemnids formerly assigned to Didemnum candidum. [ABSTRACT FROM PUBLISHER]