Online Issues

Journal Vol 50

Validation of a Method for Measuring Sperm Quality and Quantity in Reproductive Toxicity Tests with Pair-Breeding Male Fathead Minnows (Pimephales promelas)

David N. Hala, Katrien Van Look, William V. Holt, and Susan Jobling

David N. Hala, MRes, PhD, was a postdoctoral researcher at the Institute for the Environment at Brunel University in Uxbridge, London (now a research scientist at the University of North Texas). Katrien Van Look, BSc Hons, PhD, was a postdoctoral research fellow at the Institute of Zoology of the Zoological Society of London and William V. Holt, PhD, is the Head of Reproductive Biology at the same institute. Susan Jobling, PhD, is an academic at the Brunel University Institute for the Environment.

Address correspondence and reprint requests to Dr. Susan Jobling, Institute for the Environment, Brunel University, Uxbridge, London, UK UB8 3PH or email Susan.Jobling@Brunel.ac.uk.

Abstract

The fathead minnow (Pimephales promelas) is an OECD-proposed test species routinely used in reproductive toxicity trials with suspected endocrine-disrupting compounds (EDCs). The basic fecundity, endocrinology, and histopathology of reproductively active male and female fathead minnows has been well characterized, but there are few studies of the utility of male sperm concentration and motility as endpoints for use in reproductive trials. The purpose of this study was to (1) characterize the baseline sperm concentration and motility of pair-breeding male fathead minnows over their spawning cycle and (2) determine whether a repeated and nondestructive sperm sampling protocol would influence the baseline fecundity of the fish. Pair-breeding male fathead minnows that underwent sampling for milt three times a week for 4 weeks exhibited no significant changes in milt volume, sperm concentration, or motility parameters up to 6 days after each spawning event. The repeated sperm sampling procedure did, however, cause a significant lowering of spawning frequencies, although this decline did not correlate with effects on fecundity as there were no significant changes in the mean total numbers of eggs laid, fertilization, and hatching successes. This study confirmed the presence of a stable background of sperm concentration and motility parameters of pair-breeding male fathead minnows under reference conditions. The absence of any inherent “cycling” in the magnitude of these parameters over the spawning period suggests that sperm concentration and motility could be useful measures of male reproductive toxicity at the termination of tests in which pair-breeding males are at varying days post spawn.

Key Words: baseline; fathead minnow; nondestructive sampling; pair breeding; reproductive toxicity; spawn; sperm concentration; sperm motility