Development of a sperm cryopreservation protocol of Gangetic Mystus (Mystus cavasius)

Abstract

Cryopreservation is considered as one of the most useful techniques for long-term preservation of genetic material specially sperm of fish. This study focused on the development of a sperm cryopreservation protocol for indigenous near threatened gulsha (Mystus cavasius) and a number of experiments were conducted for the purpose. To collect milt, male gulsha were sacrificed and milt was suspended in extenders. Different concentrations of NaCl were used to evaluate the activation of sperm motility and it decreased as the concentration of the extending media increased, therefore, motility was completely inhibited at 0.8% and 1.2% NaCl solution when sperm suspended in Kurokura-2 and Alsevers solution, respectively. The toxicity of cryoprotectants to sperm were evaluated using two cryoprotectants, dimethyl sulfoxide (DMSO) and methanol along with the extenders, Alsevers solution and Kurokura-2 solution. DMSO and methanol with 5% and 10% concentrations produced significantly higher motility during 5 and 10 min incubation and their 15% concentration found toxic to sperm. Alsevers solution with 10% DMSO produced best equilibration (83.75±2.39%) as well as post-thaw motility (67.5±3.23%) while Kurokura-2 solution with DMSO produced similar equilibration motility (81.25±2.39%) but the post-thaw motility (50.0±6.12%) was significantly much lower than that of Alsevers solution. Sperm preserved with Alsevers solution plus DMSO produced highest fertilization, 72.5±7.5% and hatching, 56.8±5.6% while fresh sperm yielded 85.0±5.0% and 74.8±3.6% fertilization and hatching, respectively. The protocols that have been developed can be used for conservation of genetic materials of M. cavasius and other endangered fish species and new generations of them can be propagated using the cryopreserved sperm.

Progressive Agriculture 27 (4): 517-529, 2016