Abstract:

The present study was undertaken with a view to develop a simple practical protocol for the cryopreservation of spermatozoa from the endangered mahseer (Tor khudree, Cyprinidae), a well-known sport fish of India.
The study reports on the fertility of cryopreserved T. khudree spermatozoa. Immotile spermatozoa samples pooled from several males were diluted with fish Ringer’s solution (pH: 7.48) and protected with dimethyl sulfoxide (DMSO) at 5, 10 and 15%, each being subjected to equilibration periods of 10, 20, 30, 60, 70, 80 and 90 min. Diluted samples were stored in 500 µl plastic straws and cooled over liquid nitrogen (LN2) and preserved in LN2 up to 70 days. Thawing of samples was accomplished by swirling in water at 37+1oC for 10 sec. Viability of post-thawed spermatozoa was determined based on motility rate, fertilization and hatching rates of eggs and fry survival.
Very high post-thaw motility rates (92 to 98%) were obtained with 5 and 10% DMSO, equilibrated for 10, 20 and 30 min, while 15% DMSO at three equilibration periods significantly reduced (P < 0.05) post-thaw motility of spermatozoa stored up to 70 days. Very high fertilization rates of eggs were observed and interestingly, they were independent of cryoprotectant level and equilibration time. Spermatozoa protected with 15% DMSO at equilibration periods of 30, 60 and 90 min showed significantly higher (P < 0.05) hatching rates up to 41% as compared with 10 or 20 min. Maximum fry survival was obtained when spermatozoa were equilibrated up to 30 min in all three levels of DMSO. Fry produced from cryopreserved spermatozoa were normal.
The fertility studies indicate that T. khudree spermatozoa can be successfully cryopreserved using fish Ringer and 5 to 15% DMSO at an equilibration time of 10 to 90 min and viable fry is produced. Being the first report on the successful production of viable fry of mahseer from cryopreserved spermatozoa, this study will pave the way for the creation of a sperm bank for T. khudree.

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Date 2002/09/01

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