ARTIFICIAL SELECTION FOR INCREASED WHEEL-RUNNING BEHAVIOR IN-HOUSE MICE

Replicated within-family selection for increased voluntary wheel runni ng in outbred house mice (Mus domesticus; Hsd:ICR strain) was applied with four high-selected and four control lines (10 families/line). Mic e were housed individually with access to activity wheels for a period of 6 days, and selection was based on the mean number of revolutions run on days 5 and 6. Prior to selection, heritabilities of mean revolu tions run per day (rev/day), average running velocity (rpm), and numbe r of minutes during which any activity occurred (min/day) were estimat ed by midparent-offspring regression. Heritabilities were 0.18, 0.28, and 0.14, respectively; the estimate for min/day did not differ signif icantly from zero. Ten generations of selection for increased rev/day resulted in an average 75% increase in activity in the four selected l ines, as compared with control lines. Realized heritability averaged 0 .19 (range, 0.12-0.24 for the high-activity lines), or 0.28 when adjus ted for within-family selection. Rev/day increased mainly through chan ges in rpm rather than min/day. These lines will be studied for correl ated responses in exercise physiology capacities and will be made avai lable to other researchers on request.