EMBRYONIC AND LARVAL DEVELOPMENT OF THE GIANT CLAM TRIDACNA NOAE (RODING, 1798) (CARDIIDAE: TRIDACNINAE)

This paper reports on embryonic and larval development of the giant clam Tridacna noae. Spawning was induced by serotonin injection into the gonad. Unfertilized eggs had a mean (+/- SE) diameter of 101.14 +/- 0.47 mu m and spermatozoa heads were 8.92 +/- 0.09 mu mlong. Embryonic development had progressed to the 8-cell and 16-cell stages by 3 h postfertilization and to the 32-cell stage by 4 h postfertilization. Rotating gastrulae accounted for 82% of developing embryos at 9 h postfertilization. Trochophore larvae accounted for 54% of embryos at 16 h postfertilization, and 98% of larvae at 20 h postfertilization. Straighthinged (D-stage) veligers comprised 74% of developing larvae at 22 h postfertilization with mean (+/- SE) anteroposterior measurement (APM) of 146.32 +/- 0.58 mu m, dorsoventral measurement (DVM) of 118.12 +/- 0.74 mu m, and hinge length of 77.46 +/- 0.73 mu mat 24 h postfertilization. At 96 h postfertilization, 74% of veligers had settled but had retained the velum without showing development of the foot and, by 120 h postfertilization, 78% of settled veligers had become pediveligers with a probing foot. The mean (+/- SE) APM of pediveligers at 144 h postfertilization was 176.50 +/- 0.97 mu m, DVM was 151.86 +/- 1.01 mu m, and hinge length was 63.50 +/- 0.95 mu m. Gills were first observed in settled individuals 11 days after fertilization, indicating completion of metamorphosis. The methods used in this study supported successful larval culture of T. noae and provide a basis for large-scale propagation of this species.