Effects of cryoprotectant toxicity on embryos of the chinese mitten crab, eriocheir sinensis (Decapoda, Brachyura)

The response of embryos of the Chinese mitten crab (Eriocheir sinensis) in terms of survival to cryoprotectants was investigated for basic knowledge to enhance cryopreservation success of E. sinensis embryos. Five stages of embryonic development (cleavage, blastula, gastrula, eyed stage, and heart-beating stage embryos corresponding to 7, 14, 20, 26, and 31 days post-spawning) were chosen and exposed to various cryoprotectants, namely methanol (MeOH), propylene glycol (PG), dimethyl sulfoxide (DMSO), and dimethylformamide (DMF), at three concentrations (10, 15, 20%) for an experimental period of 30 min. at culture temperature (16 degrees C). The toxicity tolerance of E. sinensis embryos varied with developmental stage and cryoprotectant concentration. Cleavage and blastula embryos were very sensitive to cryoprotectant concentrations above 10%. Gastrula, eyed stage, and heart-beating stage embryos tolerated cryoprotectants to 20%, although a higher survival percentage was observed in heart beating stage embryos than in gastrula and eyed stage embryos. The survival percentage declined with an increase in cryoprotectant concentration. PG and DMF were relatively less toxic as compared to DMSO and MeOH. Based on the sensitivity to cryoprotectant exposure, heart beating stage embryos of E. sinensis are an appropriate stage for further cryopreservation.