Our understanding of the process by which individuality emerges is still rudimentary, but it is clear that the environment in which the individual develops, and its sociosexual interactions as an adult, are central to this process. This project addresses how the experiences passively acquired as an embryo interact with those of the adult, when the individual has a degree of behavioral regulation of its own environment. Behavioral and neural plasticity is at the root of these individual differences. Thus, the overall goal of the proposed research is to determine how embryonic experience and sexual experience later in life interact to affect adult male sexual behavior, and to reveal how this in turn effects the neural circuitry underlying behavior. Specifically, using the leopard gecko (Eublepharis macularius) as a model system, experiments will investigate the mechanisms involved in mediating the interaction between embryonic and adult experience. Obvious candidate mechanisms have two properties: they are influenced by the embryonic environment and they are capable of affecting sexual behavior and learning during adulthood. The mesolimbic dopamine system satisfies both these criteria and it is hypothesized that varying extent of embryonic hormone exposure organizes this system and the resulting differences mediate how the two morphs respond to experience. These studies are long-term and will involve the participation of undergraduate and graduate students for their execution. Students will be expected to present their findings at national meetings and be co-authors on papers published in peer-reviewed journals.
Sociosexual behaviors, and the mechanisms that underlie their development and activation, are especially useful in unraveling how embryonic experience modifies the adult phenotype. For example, an individual’s sexuality and aggressiveness results from heritable traits, transmitted genomically or non-genomically, as well as from environmental and social stimuli the individual experiences at different stages in its’ life history. As such it is a good model for assessing the interplay of early and late experience. The study of sociosexual behaviors spans all levels of biological organization, from the molecular through the population/social, making it relatively easy to ascribe responses to specific events. Most research to date on aggressive and sexual behavior emphasizes the differences between the sexes, yet the important element of within-sex differences has largely been ignored. As Darwin and others have noted, in virtually every sexually dimorphic trait the variation within a sex exceeds the difference between group means for males and females, and much effort is going into understanding this phenomenon. Environmental factors acting on the embryo or early in postnatal life are among the various non-genetic factors to influence the adult behavioral phenotype. Such situations and stimuli interact with sociosexual experiences in adulthood. For example, the way an animal's behavior changes in response to accumulating adult experience depends on the hormonal environment to which it was exposed in early development. We have detailed this interaction of embryonic environment and adult experience in the leopard gecko, a species that exhibits temperature-dependent sex determination. This work has revealed how the interaction between physiology, brain and behavior shapes the individual so that it responds in the appropriate manner to increase reproductive fitness.
