Cryopreservation of Sperm of an Indigenous Endangered Fish, Pabda Catfish Ompok pabda

Abstract

This study focused on the development of a protocol for cryopreservation of sperm of the endangered fish species, Pabda Catfish Ompok pabda. The activation of sperm motility was tested at various osmolalities of NaCl. The motility of sperm decreased with the increase of osmolality; it was completely inhibited at 319 mOsmol/kg. Toxicity of cryoprotectants to sperm was evaluated using dimethyl sulfoxide (DMSO), methanol, and ethanol at 5, 10, and 15% concentrations at an incubation time of 0–35 min. Five percent and 10% cryoprotectants produced 45–75% and 40–75% motility for the 5- and 10-min incubation times, respectively. Sperm incubated with 15% cryoprotectant had less motility from the beginning of incubation. The cryoprotectant was toxic to sperm. Three extenders, Alsever's solution, egg-yolk citrate, and urea egg-yolk, as well as three cryoprotectants, DMSO, methanol, and ethanol, were used for the preservation of sperm. Alsever's solution with DMSO showed best performance producing highest equilibration motility (83 ± 3.3%, mean ± SE) and postthaw motility (71 ± 4.4%) followed by levels of 68 ± 1.7% and 51 ± 1.7%, respectively, with Alsever's solution plus methanol. Sperm preserved with Alsever's solution plus DMSO produced 79.33% fertilization and 42.38% hatching while fresh sperm yielded 82% fertilization and 53.49% hatching. No statistical comparisons between cryopreserved and fresh sperm were made as we did not standardize the sperm concentration for fresh and cryopreserved sperm during breeding. Fry produced from both cryopreserved and fresh sperm were reared in aquaria for 6 weeks and no significant differences for length (P = 0.452) and weight (P = 0.431) were observed between the two groups. The protocols developed through this study can be applied for conservation of endangered Pabda Catfish, and the findings of breeding and growth studies suggest it would be useful to disseminate the cryopreservation technology to commercial hatcheries.

Received November 20, 2011; accepted September 25, 2012

ACKNOWLEDGMENTS

This research was supported by Bangladesh Agricultural Research Council (BARC) under the Core Research Programme through a project entitled Gene Pool Conservation and Stock Improvement of Some Indigenous Endangered Fish Species through Live and Cryogenic Gene Banking. Acknowledgments are also owed to Bangladesh Agricultural University Research System (BAURES) for its official support.