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The adaptive significance of female extra-pair copulation behavior was investigated in Yellow-billed Magpies, Pica nuttalli, a socially monogamous species. Research was carried out in central coastal California, U.S.A. Observations of female behavior towards extra-pair males during the breeding season suggest that females display a preference for certain extra-pair males. In addition, observations confirm that females can successfully resist male copulation attempts. However, based on a small sample, no significant difference in fledging success was found for nests at which extra-pair visits occurred and those at which they did not. Multilocus DNA fingerprinting analysis is in progress to determine the rate of extra-pair fertilizations. These data will be analyzed for correlations between female behavior towards extra-pair males and those males successfully gaining extra-pair fertilizations, and for differences in fledging success between nests with extra-pair fertilizations and those without extra-pair fertilizations.
The article is about homosexual behavior in animal. This behavior consists of various sexual activities such as the copulation of individuals having same sex, mutual masturbation, the common care over the progeny or couple formation. Homosexual behaviors have been documented in different animal groups, such as birds, reptiles, mammals, insects and spiders. The homosexuality among animals could develop under natural selection as an adaptation. For instance it can reduce of the intraspecific aggression, settle of the hierarchy in the group of non-related individual or it can be directly connected with heterosexual reproductive success. Homosexual behavior can also be a result of animal error living in unusual situation, for instance in captivity.
The study discusses molecular mechanisms of the action of estrogens (E) in the brain and their effect on sexual behavior in females. E increase the synthesis of the neuromediators: oxytocin and dopamine in the brain. E also influence K+ channel activity in neurons. Specific intracellular E receptors exist in the neurons. These receptors bind E and then activate a regulatory mechanism dependent on the protein G complex and on the cyclical AMP response element binding proteins (CREB). As a result, synaptic activity of the neurons increase and the expression of the brain-derived neurotrophic factor (BDNF) gene also take place. Moreover, E stimulate the synthesis of the sex hormone binding globulin (SHBG). SHBG plays a role as a steroids transporter and also as a signaling substance in the brain.
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