Effect of extenders, cryoprotectants and dilution ratios on the spermatological properties of cryopreserved milt of cobia Rachycentron canadum

Abstract

Cobia (Rachycentron canadum) culture depends on the availability of seeds which isaffected by asynchronous spawning and brooders availability. The possible solution forthese problems is the use of cryopreserved, high quality gametes from selected individuals.Therefore, in the present study, the effect of different extenders, different concentrationsof cryoprotectants and dilution ratios on the spermatological properties of cryopreservedcobia milt was analysed. Milt was collected from R. canadum brooders and diluted withMarine Fish Ringer’s Solution (MFRS) and 0.85% physiological saline (PS) as extendersand dimethyl sulphoxide (DMSO) as cryoprotectant at three different concentrations(5, 10 and 15%) at three dilution ratios such as 1:5, 1:10 and 1:15. Motility duration, motilitypattern, motility score and percentage of live and dead cells were analysed. The milt wasrapidly frozen employing liquid nitrogen vapour for 10 min. The milt sample diluted with PSand 10% DMSO at 1:5 dilution ratio exhibited highest post-thaw motility parameters. Keywords:Cryoprotectants, Cryopreservation, Dilution ratios, Extenders, Spermatological properties, Rachycentron canadum