EFFECT OF FREEZING RATES ON THE SURVIVAL OF PENAEID PRAWN LARVAE - A PARAMETER ANALYSIS

The objective of this paper was to develop a freeze protocol for the c ryopreservation of penaeid prawn larvae. A major difficulty in this ar ises because of incomplete permeation of the cryoprotectant into the s ystem due to a chitinous exoskeleton and a complex body organization. Ethane 1,2 diol and dimethyl sulphoxide were assessed to be the best b oth in toxicity as well as penetration assays. Combinations of ethane diol and dimethyl sulphoxide were tolerated for more than 80 minutes. Freeze rates below -1 degrees C/min led to mortality due to supercoole d fluids before the freezing of the cytoplasm or the external cryoprot ectant. Freezing rates between -1 degrees C to -3 degrees C/min caused critical damages within the thermal regimes of -35 degrees C to -45 d egrees C. Higher rates between -5 degrees to -30 degrees C/min to fina l temperatures of -50 degrees to -70 degrees C gave retrieval of 85 to 95% photomotile survivors.