DETERMINATION OF SUITABLE FREEZING MEDIA FOR CRYOPRESERVATION OF PENAEUS-INDICUS EMBRYOS

Selecting an embryonic developmental stage and a cryoprotective soluti on was the first step of our investigation on the freezing of banana s hrimp, Penaeus indicus, embryos. Among the five developmental stages s tudied, 4-cell, 16-cell, morula, gastrula, and 5-h embryos, only the l atter two were resistant enough to withstand a prolonged contact with cryoprotectants. The main obstacle to cryoprotectant penetration into the embryo was the hatching envelope. Its permeabilization by exposure to a chlorine solution was preferable to a protease-based method. Ele ven cryoprotectant additives were tested. Those with molecular weights greater than that of dimethylsulfoxide (Me(2)SO) penetrated the embry os too slowly and were abandoned. The fastest permeations after permea bilization of the hatching membrane were obtained with methanol, Me(2) SO, ethylene glycol, and 1,2-propanediol. Combinations of methanol (4 or 5%) and one of the latter (4 or 5%) were used, giving hatching rate s similar to those of the control. (C) 1994 Academic Press, Inc.