Initial Attempts on Spawning and Larval Rearing of the Blood Cockle, Tegillarca granosa (Linnaeus, 1758), in the Philippines

Abstract

Blood cockles, Tegillarca granosa (Linnaeus, 1758), were induced to spawn by temperature stimulation. Larval to spat rearing was accomplished in the hatchery facility of the Institute of Aquaculture of the University of the Philippines Visayas. The survival rate from day 1 larval stage to day 120 spat stage was 2.48 % (15,200) from the initial 614,100 eggs reared. The fertilised eggs (average size: 50.23 ± 5.18 µm in diameter) passed through the morula stage 5 h postfertilisation and reached the trochophore stage after 8 h. Day 1 D-shaped larvae (average size: 84.60 ± 3.90 µm length (l) and 66.36 ± 1.92 µm height (h)) transformed into umboned larvae by day 7. The majority of the larvae reached the advanced umbo stage by day 12 (average size: 204.52 ± 21.06 µm l and 178.24 ± 17.04 µm h). By day 20, loss of velum and foot development in larvae were observed, marking the beginning of the pediveliger stage. The growth of post-set larvae starting from the initial settling stage at day 30 (average size: 360.50 ± 52.10 µm l and 309.56 ± 34.56 µm h) to day 120 (average shell length: 3.870 ± 0.400 mm) was periodically monitored. Cockle spats had squarish shells with central elevation and visible radial ribs resembling the morphological characteristics of adult T. granosa. Only Isochrysis galbana Parke, 1949, was given as food for the cockles throughout the rearing activity. Further refining of larval and post-set rearing methodology is necessary for future mass production of cockle seeds in the Philippines.