The influence of ovarian fluid on Solea senegalensis sperm motility

Abstract

The role of ovarian fluid in fertilization has been neglected, particularly in marine species. The aim of this work was therefore to assess the influence of ovarian fluid (OF) as a potential contributor factor to sperm motility in Solea senegalensis. The specificity of interactions between sperm and ovarian fluid was analyzed using homologous and heterelogous ovarian fluid. Additional tests tried to identify the most useful concentration for improving sperm motility throughout the activation process. Ovarian fluid solutions were diluted in artificial seawater (SW) (v:v) 0 : 100, 25 : 75, 50 : 50, 75 : 25 and 100 : 0 (OF:SW). Pure ovarian fluid solutions (100%) did not promote sperm motility by themselves since they lack the osmolarity needed to trigger sperm motility. With 75% of ovarian fluid the activation solution promoted a deficient activation and the best concentrations used were 25 and 50%. The presence of ovarian fluid affected significantly total motility (TM) and progressive motility (PM) in the last seconds post activation. Progressive motility was higher at 45 s for homologous 25% OF (20.4%) than control (9.4%). Homologous 25% OF increased significantly TM and PM at 60 s post activation (32.0 and 10.5%, respectively) when compared to control (15.8 and 1.7%, respectively). Sperm velocity showed significant differences in the presence of ovarian fluid since early seconds post activation. Our data revealed an enhancement of sperm motility with ovarian fluid at low concentrations in the activation solution. There seems to be a high degree of specificity of ovarian fluid-sperm interaction since heterologous fluid had a lower performance enhancing sperm motility than homologous fluid. Our results indicated a possible important female contribution to sperm motility enhancement during the fertilization process in S. senegalensis.