2.4 Friday, Jan. 4 Functional morphology and swimming performance in flounder: are left-sided fish faster? BERGSTROM, C.A.*; PACHECO, J.; FRITZ, T.; University of Alaska Southeast; University of Alaska Southeast; University of Alaska Southeast email@example.com
Performance consequences of morphological variation within species set the stage for ecological selection to occur. In fishes, variation in body shape is known to affect swimming performance, leading to changes in ecological interactions such as predator avoidance and prey capture. However, performance consequences of one of the most conspicuous forms of body shape variation, direction of asymmetry in flatfishes, are poorly understood. Starry flounder (Platichthys stellatus), is a flatfish species that is polymorphic for asymmetry direction. The proportion of sinistral (left-sided) and dextral (right-sided) morphs exhibits a geographical cline across the species range. Differences in morphology (head shape, tail size, body depth) and stable isotope signatures between sinistral and dextral morphs suggest that they may differ in locomotor performance as well as prey acquisition. Here we tested if there were also differences between morphs in prolonged swimming endurance and fast-start velocity and acceleration. Two categories of swimming performance were tested: endurance was measured as the amount of time required to exhaust a fish swimming at constant speed in a flow chamber, and fast-start performance was measured from video of fish stimulated to induce a startle response in still water. Sinistral fish had superior performance over dextral fish in both categories, and preliminary data suggests they may also have an elevated metabolic rate. These data add to evidence of ecological segregation between asymmetry flounder morphs, implicating selection as a potential mechanism maintaining the geographical cline in their distribution.