This hygienic behaviour is notably different from that of the closely related house mouse. Both evolutionary and behavioral consequences result from the polygamous nature of the house mouse. Other predators are the weka and house mouse. Liponyssoides sanguineus is a species of mite that infests the house mouse ("Mus musculus"). The common house mouse TNF and human TNF are structurally different. These include the black rat, brown rat, fallow deer, feral swine, house mouse, and nutria. Some populations are hybrids of different subspecies, including the Japanese house mouse ("M. m. molossinus"). In mus musculus (house mouse), TRPV2 functions as a protein coding gene. For example, the standard house mouse karyotype has only telocentric chromosomes. The brown rat and house mouse are both used as medical subjects. LCMV is naturally spread by the common house mouse, "Mus musculus". Domestic mice sold as pets often differ substantially in size from the common house mouse. Experiments are often conducted in the house mouse ("Mus musculus"). "Pachygenelus monus", and "Mus musculus" (the house mouse). Introduced species (e.g., the house mouse and brown rat) are not included.