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 is
affected by asynchronous spawning and brooders availability. The possible solution for
these problems is the use of cryopreserved, high quality gametes from selected individuals.
Therefore, in the present study, the effect of different extenders, different concentrations
of cryoprotectants and dilution ratios on the spermatological properties of cryopreserved
cobia milt was analysed. Milt was collected from R. canadum brooders and diluted with
Marine Fish Ringer’s Solution (MFRS) and 0.85% physiological saline (PS) as extenders
and 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, motility
pattern, motility score and percentage of live and dead cells were analysed. The milt was
rapidly frozen employing liquid nitrogen vapour for 10 min. The milt sample diluted with PS
and 10% DMSO at 1:5 dilution ratio exhibited highest post-thaw motility parameters.

Keywords:
Cryoprotectants, Cryopreservation, Dilution ratios, Extenders, Spermatological properties, Rachycentron canadum