Heterosis of adult mouse (Mus musculus) ultrasonic vocalizing

Four sets of adult mice (Mus musculus), each comprised of individuals from two inbred strains and both reciprocal F₁ crosses, were tested during male-female and female-female dyadic encounters for their emission of 70-kHz ultrasonic vocalizations. For each sex-dyad type of each set, a single progeny mean representing both reciprocal F₁ groups was calculated and compared to (1) the average value from the inbred parents and (2) the higher mean of the within-set progenitor inbred strains. In addition to demonstrating strain-and sex-influenced ultrasonic vocalizing levels, the results indicated that for each set examined, the F₁-progeny mean amount of ultrasonic vocalizing significantly exceeded the average inbred parent value. This was true for both dyad types, providing strong evidence that ultrasonic vocalizing displlays a directional dominance mode of inheritance in both female and male mice. Moreover, for female-female dyads of all four sets and for male-female dyads of three of four sets, the F₁-progeny mean amount of ultrasonic vocalizing significantly exceeded that of the highest progenitor inbred strain. Analyses of ultrasonic vocalizing latencies yielded similar hybrid-inbred differences. Collectively, these findings are interpreted as being consistent with the notion that, for both sexes of mice, ultrasonic vocalizing is a phenotypically heterotic behavioral trait.This research was supported, in part, by a Florida State University Psychobiology Fellowship awarded to J.C.M. and by NINCDS Grant NS 15560.