Mike Bessert

MICROSATELLITE PATERNITY ANALYSIS IN THE FATHEAD MINNOW (Pimephales promelas)

Many recent studies have employed molecular markers to uncover important aspects of the mating systems of teleost fishes. Indeed, the presence and outcome of alternative reproductive tactics may go unnoticed if assayed only visually. The fathead minnow (Pimephales promelas) is a nest-building North American Cyprinid that spawns multiply and exhibits exclusive male parental care. Here, we assessed paternity using five polymorphic microsatellite loci. Sixty-five guardian males were collected with embryo-laden nests in the prairie pothole region of eastern South Dakota. DNA was extracted and a microsatellite-enriched genomic library constructed using a streptavidin-biotin protocol. Seventy-two positive clones were sequenced and 19 contained microsatellite loci. Primers were designed for seven, five of which exhibited length polymorphism. Prelimary genotypic screening of 36 individuals revealed expected frequencies of heterozygosity; thus, null alleles were not detected. Multilocus genotypes were determined for guardian males and an average of 30 embryos from each nest. A majority of nests contained clutches that were sired exclusively by the guardian male. The remaining nests included a small percentage of illegitimate embryos. In some cases, these may be the result of a nest takeover and subsequent allopaternal care; however, the low frequency of illegitimates in others is consistent with cuckolding behavior.