Anesthesia in oysters of the genus Crassostrea cultured in Brazil

Abstract

This study evaluated: 1) the time required for anesthesia induction and recovery of oysters Crassostrea rhizophorae, Crassostrea gasar and Crassostrea gigas using magnesium chloride (MgCl₂); 2) the survival after anesthesia and gonad sampling; and 3) the D-larvae generation after anesthesia. For each species, three groups of 10 animals were kept in 50 g L^-1 MgCl₂, salinity of 36 and temperature of 22°C. One control group was kept in solution without MgCl₂. Every 1 h, anesthetized oysters were recorded, sampled to determine sex and placed in clean seawater to assess recovering every 30 min. Gonad samplings were made beside the posterior adductor muscle, using 1 mL syringes and needles (0.60 x 25 mm). Factorial crosses were generated within and between anesthetized and non-anesthetized oyster groups to produce D-larvae in C. gigas. The survival after 10 days of anesthesia was 100% for the three studied species. For C. rhizophorae and C. gigas, 100% of the animals were anesthetized after 360 min and were recovered after 240 and 150 min respectively. For C. gasar, 87% were anesthetized after 720 min and recovered after >240 min. There were no significant differences in D-larvae numbers between factorial crosses. The salt MgCl₂ served as an efficient relaxant and did not cause any deleterious effect on the survival of the three studied species, or on the D-larvae generation in C. gigas.