Body streamlining is related to higher growth in Bahamian mosquitofish

Abstract

Background: Theory and empirical work indicate that streamlined body shapes (deep/wide anterior body tapering to a shallow/narrow caudal peduncle) enhance steady-swimming performance (cruising). Because steady-swimming performance reduces the cost of movement, better cruisers should have a competitive advantage. Hypothesis: More streamlined individuals have higher foraging success and competitive ability in the wild. Organism: Bahamian mosquitofish (Gambusia sp.). Times and places: Eleven populations on Abaco Island, Bahamas (291 females; 150 males) sampled in 2009 and 2010. Methods: We measured growth rate (RNA:DNA ratios) as a surrogate for foraging success and competitive ability. We obtained 16 relative warps from 10 anatomical landmarks that describe body shape. We tested for an association between growth rate and morphology using multivariate analysis of covariance. Results: Individuals with more streamlined bodies had higher growth rates across all populations. Specifically, higher growth rates were associated with shorter caudal peduncles and shallower bodies in females, and deeper heads and shorter/shallower caudal peduncles in males. These results indicate that streamlining favours greater foraging success and competitive ability.