Inducing relaxation in the queen conch Strombus gigas (L.) for cultured pearl production

Five potential relaxant chemicals were evaluated: 2-phenoxyethanol, menthol crystals, benzocaine, MS-222, and magnesium chloride to induce relaxation in the queen conch for cultured pearl production. S. gigas were exposed to each chemical and were observed continuously for 30 min. Conch were placed on the bottom of the container with the aperture facing upwards (i.e., in an inverted position). When conch returned to their ‘normal’ position, they were turned facing upwards again. This process continued until conch were unable to return to their normal position. Only 30 g L− 1 magnesium chloride induced adequate relaxation in S. gigas to attempt pearl seeding. Conch exposed to all other treatments, except 0.25 g L− 1 menthol, showed a strong ‘kicking’ (escape) reaction during the initial 2 min to 7 min of exposure. After such reaction, conch retracted into their shells and within the 30 min exposure period they showed no signs of relaxation. Conch exposed to 0.25 g L− 1 menthol did not attempt to right but slowly retracted into their shells and did not show signs of relaxation. Conch can be relaxed in 20 min with magnesium chloride. They showed an extended mantle, a relaxed foot and a slow response to physical manipulation.