CRYOPRESERVATION OF PENAEID PRAWN EMBRYOS

The cryopreservation of penaeid prawn embryos has not been successfull y carried out so far although standard protocols for several mammalian embryos are available. Penaeid prawn embryos develop in the sea water medium and hence the methodology developed for mammalian embryos, who se development takes place in the intra-uterine environment, cannot be applied for prawn embryo cryopreservation. We have successfully froze n, for the first time, the nauplii of the penaeid prawn P. indicus to -30-degrees-C and -40-degrees-C using liquid nitrogen vapour. In order to develop the freezing protocol for these embryos we have considered the following principal factors: cryoprotectant toxicity, addition an d dilution of cryoprotectant, equilibration time, freezing and thawing rates. The response of the morula stage embryos (2 h after spawning) and nauplii to several permeating cryoprotectants were studied in deta il. The hatch percentage was used as an index to evaluate survival of cryoprotectant-treated morulae and direct observation of morphology an d motility was used to assess survival of cryoprotectant-treated as we ll as frozen nauplii. Our initial attempt to vitrify the embryos was n ot successful.