Persistent Relaxation of the Adductor Muscle of Oyster Crassostrea gigas Induced by Magnesium Ion

Abstract

We developed a physiological method to open oyster shells persistently for use in an automated oyster shucking machine. When oysters (shell height, 10-13 cm; shell length, 5-7 cm; molluscous body weight, 9-22 g) were submerged in 0.369 M MgCl2 solution, their adductor muscle began to relax persistently after 17±5.9 min (mean + standard deviation) at a water temperature of 5°C and after 18±11.5 min at 15°C. The muscle did not contract when the molluscous body was stimulated with a needle. After the oysters were transferred into artificial sea water, the muscle began to contract and the oysters resumed shell movement in 78±44.2 min at 5°C and 24±5.4 min at 15°C. When 120 individuals were submerged in MgCl2 solutions at 17-18°C, cumulative persistent shell opening rates in the solutions of 0.369 M and 0.738 M were 14.2% and 63.3% for 30 min submersion, 35.0% and 72.5% for 60 min submersion, 64.2% and 83.3% for 120 min submersion, and 76.7% and 85.8% for 180 min submersion, respectively. This method for opening oyster shells persistently with the use of Mg2+ will be applicable to other bivalves for opening shells by adjusting the Mg2+ concentration and submersion time for each species. © 1995, The Japanese Society of Fisheries Science. All rights reserved.