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Embryonic development and larval and post-larval growth of the tropical scallop Nodipecten (=Lyropecten) nodosus (L. 1758) (Mollusca: Pectinidae)

Abstract:

This work describes for the first time the embryonic development of the tropical scallop Nodipecten nodosus. Larval and post-larval growth parameters and some characteristics of larvae shell morphology were also ascertained. The larvae were obtained from the induced spawning of a group of brood-stocks under controlled laboratory conditions. After fertilization, larval cultivation was carried out in conical tanks at a temperature of 26-27°C. Larval density was controlled as a function of larval growth to give 10, 5 and 3 larvae mL-1 from days 1, 3 and 8 respectively. The larvae were nourished with a 1:1 mix of Isochrysis galbana (clone T-ISO) and Chaetoceros gracílis in portions varying between 30000 and 70000 cells mL-1. Expulsion of polar groups was observed 5 and 15 min after fertilization, whereas the first cellular division occurred after 30 min. The first gastrule ciliates and trocophore larvae were noted after 8 and 18 h had elapsed, respectively, whereas prodissoconch I, or D-larvae, were discerned after 26 h. Subsequently, larvae with prodissoconch II or veliger-conch appeared at 30 h. Larval development continued for 10-12 days, followed by metamorphosis, at an approximate length of 208-230 μm. The growth of the post-larvae was evaluated for 9 days. Larval and post-larval growth corresponded to the linear equations L= 71.85 + 10.85t, r2 =0.99, and L=44.09 + 17.81t, r2 =0.94 respectively. Accordingly, larval morphology and size disparities are discussed with respect to other tropical pectinids.