INTRAUTERINE POSITION EFFECTS ON SEXUALLY DIMORPHIC ASYMMETRIES OF MONGOLIAN GERBILS - TESTOSTERONE, EYE OPENING, AND PAW PREFERENCE

A series of experiments was undertaken to both discover and explore th e causes of sexually dimorphic phenotypic asymmetries in infant and ad ult Mongolian gerbils. We found that (1) the order in which the eyes o f individual gerbil pups opened varied with their gender; right eves o f female pups opened before left eyes, while left eyes of male pups op ened before right eves, and (2) the paw that adult gerbils held in the air while maintaining a species-typical tripedal stance varied with g ender: female gerbils held their right paws in the air significantly m ore often than did male gerbils. Both order of eye opening and lateral ity of paw use while in a tripedal stance varied significantly as a fu nction of the intrauterine position which subjects had occupied as fet uses. These data implicate exposure to testosterone as a mediator of t he development of asymmetries exhibited by Mongolian gerbils.