Sperm adaptation in relation to salinity in three goby species.

In externally fertilizing species the gametes of both males and females are exposed to the influences of the environment into which they are released. Sperm are sensitive to abiotic factors such as salinity, but they are also affected by biotic factors such as sperm competition. Here we compared the performance of sperm of three goby species, the painted goby, Pomatoschistus pictus, the two-spotted goby, P. flavescens and the sand goby, P. minutus. These species differ in their distributions, with painted goby having the narrowest salinity range and sand goby the widest. Moreover, data from paternity shows the two-spotted goby experiences the least sperm competition while in the sand goby sperm competition is ubiquitous. We took sperm samples from dissected males and exposed them to high salinity water (31 PSU) representing the North Sea and low salinity water (6 PSU) representing the brackish Baltic Sea Proper. We then used computer assisted sperm analysis (CASA) to measure the proportion of motile sperm and sperm swimming speed 10 min and 20 hrs after sperm activation. We found that sperm performance depended on salinity but there seemed to be no relationship to the species' geographical distribution in relation to salinity range. The species differed in the proportion of motile sperm but there was no significant decrease in sperm motility during 20 hrs. The sand goby was the only species with motile sperm after 72 hrs. This article is protected by copyright. All rights reserved.