Equalizing sperm concentrations in a common carp (cyprinus carpio) sperm pool does not affect variance in proportions of larvae sired in competition
Résumé
Proportions of offspring from five common carp contributing to a sperm pool composed of equalized sperm concentrations (N-progeny) or equal sperm volumes (V-progeny) were each compared to a uniform distribution. Four microsatellite markers (MFW1, MFW6, MFW7, MFW28) were used to determine the paternity of the progeny. The homogeneity of offspring numbers from each male for the two types of progeny, were tested using an exact test for the likelihood-ratio chi-square. Numbers of offspring in the progeny groups were highly variable (0.4–50% in V-progeny, 2.4–41.2% in N-progeny) and highly significantly different as shown by Pearson chi-square statistics (χ2 = 189, 4 df, P < 0.0001 in V-progeny and χ2 = 139, 4 df, P < 0.0001 in N-progeny). Significant heterogeneity between treatments (P < 0.05) together with reduction of χ2 value from 189 to 139 showed that equalization of sperm concentration reduced heterogeneity in numbers of offspring. Number of sperm per male, sperm motility (71–98%), sperm velocity (97–155 μm s− 1) and control hatching rates (81–91%) all affected the observed number of offspring sired by each of the males, but the high variability in proportion of progeny among the 5 males remained unexplained.