Larval development of the southern flounder Thysanopsetta naresi from Chilean Patagonia

A detailed description of the larval development of the southern flounder Thysanopsetta naresi is carried out for the first time. The study is based on larvae collected in oceanographic cruises carried out in the fjords of southern Chile. The larvae comprised a range from 2.8 mm to 22.4 mm body length (BL). One of the most distinguishing characters of the larvae is the early appearance of pigmentation, starting in preflexion notochord larvae and covering the entire body in the postflexion and transformation stages, except the caudal peduncle. During the advanced postflexion stages, a typical pattern of pigmentation was observed on the base of the dorsal and anal fins. The ray formation sequence of fins is caudal, dorsal, anal, pelvic and pectoral. The sequence of the osteological development of the larvae is described, particularly of the vertebrae and caudal skeleton. Right eye migration starts at 11 mm BL and the transformation is complete at > 23 mm. The characters described herein allow the identification of T. naresi larvae and separate them from the larvae of other flounder species that can be found in the Patagonian region.