Does Red Junglefowl Comb Size Predict Sperm Swimming Speed and Motility

Abstract

Assurance of fertility is one of many selection pressures that have been hypothesized to drive female selectivity in mate choice. Male ornament expression could signal fertility and allow females to select mates to maximize the number of eggs fertilized. If so, expression of the male ornament(s) should correlate positively with some measure of fertilising efficiency. In male red junglefowl (Gallus gallus), comb size is the only male morphological trait repeatedly shown to predict female mate choice. Comb size in two different groups of yearling male junglefowl was compared with a composite variable assessing sperm speed and motility. This variable, derived through principal component analysis, captured variation in the percent of sperm motile, swimming speed of sperm, and directional swimming speed of sperm. In one group of males, sperm movement was greater in smaller combed males. In the other group, sperm movement was uncorrelated with comb size. Thus we found no evidence that females will gain fertilit...