does a sexually selected trait represent a burden in locomotion?

Abstract

This study tested the hypothesis that in Montezuma swordtail Xiphophorus montezumae, bearers of longer swords would face higher costs in terms of swimming speed than males with shorter swords, as a result of differences in total body length when natural swords were present. Variation in natural sword length, however, did not appear to be correlated with the cost in terms of critical swimming speed, U-crit. On the other hand, the mean U-crit of males with the sword excised was 21% higher than that when natural sword was present. This study suggests that the sword of Montezuma swordtail represents a disadvantage in terms of swimming performance regardless of the differences in sword length.