Semen characteristics and optimisation of sperm cryopreservation protocol of a commercially important minor carp Labeo gonius (Hamilton, 1822)

This study aimed to develop a suitable protocol for the semen cryopreservation of a commercially important minor carp Labeo gonius, to aid in seed production and ex-situ conservation efforts. Semen characteristics were analysed, revealing a pH ranging between 7.4-7.7, an average osmolality of 276±15 mOsmol kg-1 and sperm counts ranging from 25.4×109 to 34.2×109 cells ml-1. Nine extenders were screened and three (8, 9B and 9C) were selected based on their high sperm activation (over 70% with water as activator) and sperm motility time (>40 s) after Principle Component Analysis (PCA). Cryopreservation involved a milt to diluent ratio of 1:6, with 10% DMSO as a cryoprotectant. Diluted milt was loaded into 0.25 ml straws, equilibrated and stored in liquid nitrogen. The selected extenders (8, 9B and 9C) demonstrated hatching rates of 61.1±0.23, 81.3±0.19 and 83.7±2.7%, respectively and survival rates of 44.6±1.2, 45.0±2.64 and 46.7±1.52%, respectively. The control group using fresh sperm had hatching and survival rates of 84.99±0.88 and 48.6±1.52%, respectively. Extenders 9C and 9B, containing 10% DMSO and sugar, showed significantly higher hatching and survival rates than extender 8. However, there were no significant differences in hatching or survival rates between cryopreserved sperm and the control group, except in extender 8. The results clearly indicated that, extenders 8, 9B and 9C supplemented with 10% DMSO can be recommended for semen cryopreservation of L. gonius, contributing to ex-situ conservation and quality seed production. Keywords: DMSO, Ex-situ conservation, Labeo gonius, Sperm cryopreservation