Postlarvae of Mytilus edulis platensis: (1) outer view of a postlarva 400 µm long, with an eye spot (ES) and naturally deprived of adventitious hairs; (2) inner view of a postlarval shell; (3) general view of an 850 µm long shell – a marked growth line delimits the prodissoconch II; (4) close up of the umbo of an 850 µm long shell. (LI) Larval ligament, (Pr) provinculum (hinge), (PrT) provincular or primary teeth, (PTI) posterior teeth I. Figures 2–4 are SEM micrographs; the periostracum was previously removed.