Sperm fatty acid composition as an indicator of quality and cryotolerance in blue catfish, Ictalurus furcatus.

There is a lack of biomarkers that can be used to predict fresh and frozen-thawed sperm quality for the commercially important blue catfish, Ictalurus furcatus. Sperm membranes are composed of various fatty acids (FAs) that have been linked to reproductive success across other animal and fish taxa, making it a potential biomarker. The objectives of this study were to (i) compare sperm FA percentages between fresh and cryopreserved male groups; and (ii) use sperm kinematics of fresh and cryopreserved males to create "good" (i.e. fast swimming sperm kinematics) and "bad" (i.e. slow swimming sperm kinematics) quality groups, then compare FA percentages of the groups to pinpoint physiological biomarkers of fresh and frozen-thawed sperm quality and cryotolerance. We found significant differences between fresh and cryopreserved sperm where fresh sperm had significantly higher ratios of n-3:n-6 and EPA:ARA as well as n-3 PUFAs and MUFAs, while cryopreserved sperm had higher concentrations of saturates. Cryopreserved sperm from good and bad males also had differences, such as a significantly higher concentration of saturates in good males and significantly higher concentrations of MUFAs, n-6 PUFAs, n-3 PUFAs, and total PUFAs in bad males. Lastly, low levels of MUFAs and n-6 PUFAs in fresh sperm resulted in higher post-thaw sperm kinematics. This knowledge can now be used to create additional biomarkers of sperm quality and to formulate the FA profile of catfish diets to improve sperm quality, thereby, improving their ability to handle the stressors of the cryopreservation process.