Fertilizability of cryopreserved and cadaveric fish spermatozoa of freshwater catfish Pangasius sutchi (Fowler, 1937)

Fertilizability of cryopreserved and cadaveric fish spermatozoa was attempted in the freshwater catfish Pangasius sutchi. Cryopreservation of spermatozoa was done with three cryoprotectants for short time storage (30 days). Whereas the spermatozoa obtained from the cadaveric fish were stored at ?20°C (30 days) without any cryoprotectants. Cryoprotectant toxicity assay showed maximum motility of 88.53 ± 2.01% and viability of spermatozoa (96.19 ± 4.92%) with 15% of Dimethyl acetamide (DMA) at 15 min equilibration time. Whereas Dimethyl sulfoxide (DMSO) (15%) registered moderate level of motility and viability 79.23 ± 2.02% and 80.89 ± 2.1%, respectively. However, the methanol (MeOH) (20%) resulted in low percentage of motility (58.6 ± 0.9%) and viability (68.6 ± 0.9%). Scanning electron micrographs further showed no significant deformity on the surface topography of spermatozoa of cadaveric fish as well as cryopreserved with DMA (15%). The results indicated that 15% of DMA with hanks balanced salt solution (HBSS) extender at a dilution ratio of 1:10 at ?80°C proved to be suitable for cryopreservation of spermatozoa in P. sutchi. This may be due to the osmolality of HBSS similar to seminal plasma of P. sutchi. Further studies on motility, viability and fertility potential of spermatozoa revealed 73.62 ± 1.61%, 88.34 ± 1.05% and 54 ± 2.2%, respectively, with DMA (15%). On the other hand, cadaveric fish sperm registered 57.12 ± 2.32%, 63.45 ± 0.94% and 25.33 ± 1.53% of motility, viability and fertilizability respectively. Thus, this study augments the feasibility of using cryopreserved as well as cadaveric fish spermatozoa for the seedling production in the fresh water catfish P. sutchi.