Anesthetic sampling and the tissue regeneration potential of oysters: A study with Crassostrea hongkongensis

The use of an appropriate amount of anesthetic can prevent the sacrifice of oysters during experimental sampling or seedling rearing. In this study, we assessed the effects of air exposure and three concentrations of magnesium chloride (10, 40, and 70 g L–1) on the anesthetic efficiency for Crassostrea hongkongensis. We examined the recuperative capacity of the oysters post-tissue sampling. The results indicated that 36 h of air exposure could significantly enhance the anesthetic efficiency of C. hongkongensis while ensuring the oysters’ survival. A 40 g L–1 solution of magnesium chloride had the optimal anesthetic effect on C. hongkongensis across all oyster sizes. In addition, smaller oysters (119.10 g) had a higher relaxation rate than larger oysters (191.00 g). The oysters anesthetized with 40 g L–1 magnesium chloride also demonstrated the best recovery. No deaths were observed among the non-anesthetized oysters, anesthetized-recovered oysters, or non-recovered oysters during a seven-day post-farming period. In terms of live sampling, the control group (100 %), gonad group (100 %), mantle group (98.67 %), gill group (89.33 %), and adductor muscle group (97.33 %) all showed high survival rates after anesthesia. Observation of tissue growth post-sampling revealed the presence of focal green areas in tissues between days 7 and 14. By day 30, the adductor muscle and mantle tissues had fully healed, and the regrown tissue in the gills had approached its original length. A 40 g L–1 magnesium chloride solution had no significant effects on gametes in terms of fertilization rate, growth rate, and attachment rate. The present findings indicated that C. hongkongensis could be effectively anesthetized using a 40 g L–1 magnesium chloride solution following 36 h of aerial exposure. Post-anesthesia tissue and gamete sampling did not result in significant mortality, and the tissues had fully recovered within 30 days post-sampling. The anesthesia did not have any adverse effects on the progeny.