First record of the genus Onchidoris (Gastropoda: Nudibranchia: Onchidorididae) from the South Atlantic Ocean, with the description of a new species from Brazil

A new species of the genus Onchidoris is described from the south-western Atlantic, on the coast of Brazil, in the States of Rio de Janeiro and Sao Paulo. To date, the genus Onchidoris is known almost exclusively from the northern hemisphere, especially the Atlantic coast of Europe and the Mediterranean Sea. The single previous record from the southern hemisphere is Onchidoris maugeansis, described from Australia. This is the first record of the family Onchidorididae from the coast of Brazil. Onchidoris brasiliensis sp. nov. is very similar to Onchidoris depressa, from England and the northern coast of Spain, but is distinguished by the presence of a triangular protuberance on the edge of the inner lateral radular tooth and a wide closed branchial circle with tubercles inside. Furthermore, the egg mass of O. brasiliensis sp. nov. contains a single row of eggs, whereas that of O. depressa has multiple rows. Onchidoris brasiliensis sp. nov. has lecithotrophic development, the first record of this type of development in the genus. There is a relationship between O. brasiliensis sp. nov. and the bryozoan Parasmittina protecta.