The relationship between sperm energetics and sperm function is poorly known, but is central to our understanding of the evolution of sperm traits. The aim of this study was to examine how sperm morphology and ATP content affect sperm swimming velocity in the zebra finch Taeniopygia guttata. We exploited the high inter-male variation in this species and created extra experimental power by increasing the number of individuals with very long or short sperm through artificial selection. We found a pronounced quadratic relationship between total sperm length and swimming velocity, with velocity increasing with length up to a point, but declining in the very longest sperm. We also found an unexpected negative association between midpiece length and ATP content: sperm with a short midpiece generally contained the highest concentration of ATP. Low intracellular ATP is therefore unlikely to explain reduced swimming velocity among the very longest sperm (which tend to have a shorter midpiece).

ReadMe file for data files associated with the manuscript “Sperm morphology, ATP concentration and swimming velocity: unexpected relationships in a passerine bird”This readme file describes the data files accompanying the above publication.Experimental males summary dataThis data file contains all the data collected from each experimental male. Data include semen characteristics (e.g. sperm measurements) and morphological data (e.g. body weight).Microplate sample repeatabilityThis is the data file containing the data from experimental males used to test the repeatability of ATP content across triplicate wells. Descriptions of variables are included in the R code file “Sperm morphology, swimming velocity and ATP content.r”.R script for analysesThis file provides the code for the analyses carried out in the manuscript.Dryad script ATP MS 29.7.16.R