Meeting Abstract
When one considers what makes a fish fast, it is tempting to assume that having larger fins would result in better performance: more surface area would be available to push against the water, or the substrate in a terrestrial tail-flip jump. Alternatively, it might be that excessively large fins could heighten the effect of drag in the water and also stick to the surface substrate during terrestrial jumps, ultimately hindering performance in both environments. We sought to determine how median fin size affects jumping on land and out of the water by exploiting variation in fin size in the Siamese fighting fish, Betta splendens. Selective breeding has produced males with large, elaborate median fins, while females retain smaller fin morphology, closer to wild type Betta. We used high-speed video to capture aquatic and terrestrial jumps, and measured jump duration, height and velocity with ImageJ. We made two comparisons: (1) females to unaltered males, and (2) a paired comparison of the males in their unaltered state to themselves after we had trimmed their median fins to approximately 75%, 50%, and 25% of their original area. We found that males with large, elaborate median fins exhibited poorer performance in jump duration, jump height, and maximum velocity when compared with either females or to themselves with fins trimmed. Thus, the alternative hypothesis, that increased fin size above a certain area is detrimental to jumping performance, is supported by our data. Selective breeding for ornamental form has resulted in reduced locomotor performance in male Betta splendens.
