Assessment of Larval Morphological Traits and Morphometry in Picnic Seabream, Acanthopagrus berda (Forsskal 1775) in Captivity for Developing Identification Keys

Abstract

Morphological changes during metamorphosis from larvae to juvenile stage vary considerably among teleosts. Metamorphosis in Acanthopagrus berda, a commercially important sparid, recorded using simple microscopy in captivity, revealed progressive changes in pigmentation, band formation, development of fins, and other morphological features. Larvae on 2 day post hatch [dph] (2—3 mm total length [TL]) exhibited an open mouth and pigmented eyes, and on 12 dph (6—7 mm TL), notochord flexion initiated with marked development in dorsal, anal and caudal fin formation. Larvae on 8 dph (3—4 mm TL) exhibited an initial internal pigmentation in the buccal cavity and 10 dph larvae were observed with an initial external pigmentation on the cephalic region. On 22 dph (11—12 mm TL), vertical band formation was initiated at the anterior portion of the larval body and proceeded posteriorly. The sequence of fin formation was in the order of pectoral, caudal, dorsal and anal fins, followed by the pelvic fin. On 45 dph (25—28 mm TL) miniature adult with fully formed silvery scales and lateral line emerged in captivity. TL bared a positive correlation with the larvae's vertical mouth opening and eye diameter. The coefficient of variation in body weight of the fish has reduced from 38 to 25% from larvae to juvenile. Information on the metamorphosis of the larvae of the species will help to act as an identification key for planktonic larvae collected from the natural environment.