TOXICITY TOLERANCE OF OYSTER EMBRYOS TO SELECTED CRYOPROTECTANTS

With the aim of establishing cryopreservation protocols for oyster (Cr assostrea gigas) embryos, toxicity of single or combined cryoprotectan ts to oyster embryos was investigated. In experiments on the toxicity tolerance of oyster embryos, four conventional cryoprotectants, namely , acetamide (A), dimethyl sulfoxide (DMSO), ethylene glycol (EG) and p ropylene glycol (PG), with concentrations from 1 to 5 M were used to t est the toxicity tolerance of oyster embryos at eight different develo pemental stages. On a molar-equivalent basis, DMSO appeared to be less toxic to PG, EG and acetamide in general. Oyster embryos were toleran t to low concentrations of all cryoprotectants tested in the range fro m IM to 2 M for all developmental stages. Early stage embryos were mor e vulnerable to high concentration (4 M and 5 M) cryoprotectants teste d than late stage embryos. Experiments were subsequently performed to study the combined effects of DMSO and acetamide adding trehalose or g lucose in reducing toxicity to 4-hour oyster embryos. The use of treha lose or glucose reduced toxicity of high cryoprotectant concentrations . Survival was higher when DMSO was combined with acetamide than when using DMSO or acetamide alone at high concentration (5 M). By adding t rehalose to combined 5 M DMSO and acetamide (total concentration) an a verage survival rate of 67 +/- 7 % was obtained in contrast to 8 +/- 5 % or 2 +/- 1 % survival when testing with 5 M DMSO or 5 M acetamide, respectively.