BURNESS, G.P.*; SCHULTE-HOSTEDDE, A. I.; CASSELMAN, S. J.; MOYES, C. D.; MONTGOMERIE, R.; Queen’s University; Queen’s University; Queen’s University; Queen’s University; Queen’s University: Do sneaker male bluegill sunfish produce physiologically superior sperm?

Sexually mature male bluegill sunfish (Lepomis macrochirus) display two distinct life histories. Some individuals delay reproduction until ca. 7 years of age, build nests and actively court females. Other males mature at a younger age and smaller size, and adopt a cuckolder tactic. We hypothesized that these smaller �sneaker� males would compensate for their size disadvantage at the gametic level. We examined the motility and energy stores of sperm from males of both life-history strategies. During the first 15 seconds following activation, sperm from sneaker males tended to swim faster than sperm from parental males. This greater swimming speed disappeared by ca. 45 seconds, at which point the sperm of parental males swam faster. Higher initial swimming speeds of sperm from sneaker males likely resulted from the sperm�s higher starting ATP levels. The rate at which ATP was utilized by sperm did not, however, differ between the two reproductive tactics, suggesting the existence of a trade-off between sperm swimming speed and swimming duration. Our data suggest that sneaker males may be compensating for their size disadvantage by producing physiologically superior spermatozoa.