No abstract

Digging behaviors of several inbred strains of laboratory mice and some of their crosses were examined in three contexts. In laboratory burrow boxes, C57BL/6Abg mice constructed more sophisticated burrow systems than did BALB/cAbg mice. Their Fi hybrids built burrow systems more complex than either parental strain. The same pattern of genetic influence was observed in an outdoor pen. In an escape task that required digging, BALB/c mice escaped more quickly than did C57BL/6 mice; their Fi hybrids showed dominance toward the BALB/c phenotype. These results indicate that behavioral polymorphisms in digging behavior, which may relate to habitat selection, have a genetic basis. The dominance and overdominance toward the better digging parental strain in each type of task suggest the possible evolutionary importance of these digging behaviors.Burrowing behaviors are common to rodent species and appear to offer advantages such as protection from predators and from the extremes of weather (Ruffer, 1965). These behaviors seem to have strong genetic components that persist under conditions of domestication (Boice, 1977) and that differ markedly in specific kinds of digging (King & Weisman, 1964;Webster, Williams, Owens, Geiger, & Dewsbury, 1981). Polymorphism of digging behaviors across species may be related to habitat selection. King and Weisman surmised that laboratory digging behaviors of different Peromyscus species reflect differences in utilization of their respective habitats. Webster et al. found considerable differences in digging among 12 muroid rodent species, a result suggesting that variability in habitat selection/utilization might also exist within species (Wecker, 1963).With inbred strains of Mus, the rodents that permit detailed genetic analysis of We thank Ellen Elias for data collection.

A genetic analysis of sedative-hypnotic response in selectively bred Long-Sleep (LS) and Short-Sleep (SS) mice showed LS mice to be more depressed by acetaldehyde, ethanol (ETOH), and t-butanol, but less sensitive to pentobarbital. Intermediate inheritance was shown by the two reciprocal F1 hybrids for the alcohols, but dominance to the LS genotype occurred for the aldehyde and the barbiturate. At several subhypnotic doses of ETOH in two experiments, LS mice showed less locomotor stimulation and greater disruption of coordination than the SS mice. The two reciprocal F1 hybrids did not differ from one another and had dose-response curves intermediate to the two parental lines. Study of the effects of t-butanol on locomotor activity revealed a pattern of line differences similar to that for ETOH. The genetic selection for LS and SS mice appears to have differentiated loci that pleiotropically influence a variety of behavioral responses to alcohols.

Mice selectively bred for marked response to hypnotic doses of ethanol (long-sleep, LS) respond to subhypnotic doses of ethanol (ETOH) with less stimulation of locomotor activity than their short-sleep (SS) counterparts. This assessment was made by comparing ETOH-induced alterations in locomotor activity to an untreated baseline within individual subjects, and to a saline-treated control group. A correlational study, using the same method in F2 generation hybrids of the LS and SS lines, produced a negative correlation (-.36) between locomotor stimulant effects of a subhypnotic dose of ETOH and length of loss of the righting reflex following a hypnotic dose. This relationship also appeared in a factor analysis of baseline locomotor activity, ETOH-stimulated activity, and depressant response variables. The genetic selection for LS and SS mice appears to have differentiated loci that influence more than one type of behavioral response to ETOH, an example of pleiotropism.