Effects of selection by the Percoll density gradient method on motility, mitochondrial membrane potential and fertility in a subpopulation of Atlantic salmon (Salmo salar) testicular spermatozoa

Abstract

The aim of this study was to evaluate effects of selection using the Percoll density gradient method on motility, mitochondrial membrane potential (Delta Psi Mit) and fertility in a subpopulation of testicular spermatozoa obtained from Atlantic salmon (Salmo salar). Samples were divided into three groups: Control (C), T1 (45/90 % Percoll (R)) and T2 (45/60 % Percoll (R)). Sperm motility was evaluated using CASA (Computer-Assisted Sperm Analysis), Delta Psi Mit using flow cytometry, and fertility evaluating whether cleavage of fertilised eggs had occurred after 16 h of incubation at 10 degrees C. Results indicate that motility was greater in T1 (92 +/- 2.91 %) and T2 (89 +/- 2.88 %) than in the Control (83.2 +/- 2.04 %). The percentage of Delta Psi Mit was 88.3 +/- 0.58 % and 85 +/- 2% for T1 and T2, respectively, compared to 35 +/- 6.24 % for the control. The fertility rates were 76 +/- 9.1 % and 70 +/- 8.1 % for T1 and T2, respectively, compared with 66 +/- 12 % for the control. The kinetic characteristics for T1 were curvilinear velocity (VCL): 92.44 +/- 21.12 mu m/s, average path velocity (VAP): 85.87 +/- 21.83 mu m/s; and for T2 VCL was 78.69 +/- 17.63 mu m/s and VAP was 73.62 +/- 17.08 mu m/s. The results indicate sperm motility and Delta Psi Mit were greater in T1 and T2 compared with the control (P < 0.05). Similarly, there was an increase in the fertilisation rate compared to the control. The results from this study are the first where sperm quality variables were evaluated for Salmo salar testicular sperm using the Percoll (R) density gradient method.