CRYOPROTECTANT TOXICITY IN PENAEID PRAWN EMBRYOS

Cryopreservation of penaeid prawn embryos has definite applications in the aquaculture industry. It can be considered a viable alternative t o solve the ''seed'' scarcity faced during the ''lean'' season. presen tly, there is no protocol for the cryopreservation of prawn embryos. A s a study of cryoprotectant toxicity is an essential prerequisite for the development of a cryopreservation protocol, this study focuses on the toxicity of seven well known permeating, low molecular weight cryo protectants: glycerol, formamide, acetamide, methanol, propylene glyco l, dimethyl sulfoxide (Me(2)SO), and ethylene glycol (EG). In the cryo protectant toxicity experiments embryos were exposed to cryoprotectant solutions at 15 degrees C for a period of 15 min, whereas the toxicit y neutralization experiments were conducted at 28 degrees C with an ex posure time of 15 min. The widely used permeating cryoprotectant, glyc erol, was toxic to morula stage embryos at concentrations >0.5 M. This study shows that the toxicity tolerance of Penaeus indicus embryos va ries with the developmental stage, the later stages being more resista nt. Morulae did not tolerate any cryoprotectant above 5 M, whereas the nauplii had survival rates of 45% in 12.5 M methanol and 78% in 6.4 M EG. The toxicity neutralization experiments do not seem to indicate a ny specific toxicity-blocking mechanism in Me(2)SO toxicity reduction by EG. Based on the response to cryoprotectant toxicity, nauplius stag e larvae of penaeid prawns can be considered a suitable stage for cryo preservation, both by the conventional slow cooling method and also th e vitrification technique as it allows use of high levels of cryoprote ctant. (C) 1996 Academic Press, Inc.