Pheromonal effects on germ cells of house mouse males: possible evolutionary consequences

Abstract

It is well known that in mice some pheromones modify reproductively important features. But the genetic mechanisms underlying such changes remain insufficiently studied. Here we show that in laboratory mice (Mus musculus L.), volatile signal 2,5-dimethylpyrazine excreted by donor stressed females increases the level of structural chromosome aberrations and other meiotic disturbances in spermatocytes of recipient males after nasal contact with the volatiles via sniffing. These chemosignals (i.e. pheromones) also induce abnormalities of sperm heads in the recipient mice. We assume that visible macro-damages at the chromosome level in meiotic cells are marks of a more widely disturbing effect (not only macro-but also micro-damages) of some olfactory signals in meiotic cells. It is most probable that the effects of volatile cues are mediated by the nervous system of the recipient organism. While gross chromosomal aberrations lead mainly to death of damaged cells, some of them (micro-damages of the chromosomes) might reach spermatozoa, and we detected part of them as anomalous sperm heads. Such abnormalities can reduce the fertilizing capacity of sperm. Moreover, some of the mutations induced by density-dependent volatile chemosignals can reach the progeny and influence the quantity and genetic quality of future generations. Possible microevolutionary consequences are discussed.