Viability of Tor fish spermatozoa (Tor soro, Valenciennes 1842) 48-hours cryopreservation: the effects of duck egg yolk as a natural cryoprotectant

Abstract

Tor is endemic freshwater fish in Sunda, locally known as kancra or dewa, which inhabits rivers with clean and clear water quality. In local customary and cultural perspectives, it is sacred fish whose populations have persistently depleted into scarcity. Sperm cryopreservation is one of many techniques to maintain its survival from extinction by inducing breeding at the reproductive stage. This study was designed to determine the effects of duck egg yolk as a cryoprotectant on the viability of Tor fish spermatozoa after 48 hours of cryopreservation. It employed the stripping method to obtain the fish semen and used diluent solution consisting of fish ringer solution, 10% methanol, and duck egg yolk in various concentrations (0%, 5%, 10%, 15%, 20%, 25%), with 1:10 ratio of sperm to diluent solution. These samples were equilibrated at 5°C for 10 minutes, frozen at -10°C for 48 hours in a freezer, and then defrosted at 40°C for 1 minute. The One-way ANOVA revealed statistically significant differences (p <0.05), and the post-hoc Tukey test also showed statistically significant differences (p <0.05). Because the 10% duck egg yolk produced the highest viability (averagely 83.75±1.71%), this concentration is the best cryoprotectant for optimal Tor spermatozoa cryopreservation.