Cold sensitivity of Astyanax altiparanae embryos and the performance of fatty acids and cryoprotectants in the larval viability maintenance

Introduction: Cryopreservation of fish embryos is still a technique under development. The main problems are the sensitivity of fish to low temperatures and the cryoprotective substances needed to prevent the formation of ice crystals. Another problem caused by the abrupt drop in temperature is the alteration of membrane phospholipids during solidification, thus increasing membrane tension. In this sense, increasing the degree of unsaturation of membrane phospholipids can increase their fluidity and resistance to freezing.

Objective: This study aimed to evaluate the effect of cooling on embryos of Astyanax altiparanae from parents fed an omega-3-rich diet and the effect of propylene glycol (PRO P) on larval hatching. Methods: Two groups were formed and fed a commercial diet containing 32% crude protein, at a rate of 1% of total body weight per day, for 12 months: one fed only the commercial diet (GC), and the other fed the commercial diet supplemented with 5% marine fish oil (GO). Six somite embryos were used. Were placed in incubators and inserted into Petri dishes containing 50 mL tap water or 50mL PROP (1M, 2M), placed in incubators B.O.D. to cooling.

Results: Hatching rate of GO was (P <0.05) higher than in GC. At 15°C without cryoprotectant (GC=51.0±26.78%, GO=75.0±18.5%), PROP 1M (GC=58.3±33.28%, GO=83.3±27.21%). At 5°C, only hatching in the GO PROP 1M (18.39±8.34%). Embryos exposed to the cooling treatments produced larvae with morphological deformations.

Conclusion: A. altiparanae embryos exhibit low temperature sensitivity; cryoprotectants increased their cooling resistance, and GO embryos were more resistant to cold, but more sensitive to cryoprotectants.