Anatomy of the pallial cavity and associated organs in three species of Olivella (Mollusca: Neogastropoda: Olividae) from Brazil.

Olivella Swainson, 1831 is a genus of small marine benthic gastropods found worldwide, represented by 117 valid species in 17 subgenera usually defined by conchological features such as colouration, size, shape and shell sculpture. Despite some conchological research on species in the family Olividae Latreille, 1825, the soft anatomy of Olivella species is still poorly studied. The present study aims to describe and compare the morphology of the pallial cavity and its adjacent structures in three species of Olivella from the Brazilian coast: Olivella (Olivella) floralia (Duclos, 1844), Olivella (Olivella) nivea (Gmelin, 1791), and Olivella (Niteoliva) minuta (Link, 1807). We suggest that some conchological (e.g. reabsorption of the columella or not; presence or absence of the operculum) and soft anatomical (e.g. placement of the posterior mantle tentacle, morphology of osphradium and reproductive system) features are useful to better distinguish between the subgenera Olivella and Niteoliva. Such characters have a potential role in taxonomic decisions and hypotheses regarding subgenera and a better understanding of evolutionary relationships within Olivella. [ABSTRACT FROM AUTHOR]