Direct development in the intertidal South American shell-less Onchidella marginata (Couthouy in Gould, 1852) (Gastropoda: Heterobranchia: Onchidiidae)

Abstract

This work shows evidence of complete encapsulated development of Onchidella marginata forthe first time in South America. Recent common ancestry was suggested for geographicallyseparated New Zealand sub-Antarctic and South American populations of Onchidella. Thiscould be explained as driven by passive rafting mediated by circumpolar ocean currents. Insamples from mussel- and algal-beds in intertidal rocky shores from the southern tip ofSouth America (Tierra del Fuego Island, Argentina) we found both adults and egg masses,and crawling hatchlings were observed.