Browsing by Subject "Arginine vasotocin"
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Item Hormonal correlates of coloration and sexual change in the hermaphroditic grouper, Epinephelus adscensionis(2010-12) Kline, Richard Joseph, 1970-; Khan, Izhar A.; Holt, J. (Joan); Thomas, Peter; Godwin, John; Hofmann, Hans A.Hermaphroditism, associated with territoriality and dominance behavior, is common in the marine environment. Male sex-specific coloration patterns and behavior are particularly evident in species where males are territorial and guard harems of females such as wrasses and groupers. Protogynous hermaphrodites that change sex from female to male are good models to study sexual behavior and related changes in the brain due to their abilities to reorganize their sexual phenotype as adults. Two hormones produced in the brain and implicated in the process of sex-specific behavior and reproductive development are arginine vasotocin (AVT) and gonadotropin releasing hormone (GnRH). While a wealth of data exists regarding these hormone systems separately, little is known about linkage between these two systems. Especially there is no data tracking these two systems together in any protogynous fish. This study was conducted to test the hypothesis that coordinated interactions between AVT and GnRH facilitate the process of behavioral and gonadal sex change in the rock hind Epinephelus adscensionis. Four topics were addressed to investigate the relationship between behavior and reproduction: i) rock hind sex change, sexual characteristics and conditions causing sex change to occur in captivity were detailed as a basis for examining the AVT system and GnRH during this process, ii) the distribution of a vasotocin V1a type receptor identified in rock hind brain was examined for the first time in a fish species using a custom designed antibody then the receptor protein was co-localized with GnRH producing cells within the brain to confirm that a pathway exists for AVT action on GnRH, iii) levels of AVT, AVT receptors, and GnRH messenger RNA (mRNA) were compared between male and female rock hind phenotypes, and iv) female rock hind at early stages of sex change were compared for brain mRNA expression of AVT, AVT receptors, and GnRH to determine the order of hormonal change during the process of sexual inversion in this species. This study provides a better understanding of the relationship between sex-specific behavior and reproductive development via AVT and GnRH systems that are conserved in all vertebrates.Item Molecular mechanisms of phenotypic plasticity in Astatotilapia burtoni(2011-12) Huffman, Lin Su; Hofmann, Hans A.; Crews, David; Gore, Andrea; Ryan, Michael; Zakon, HaroldThe ability of an animal to respond and adapt to stimuli is necessary for its survival and involves plasticity and coordination of multiple levels of biological organization, including behavior, tissue organization, hormones, and gene expression. Each of these levels of response is complex, and none of them responds to stimuli in isolation. Thus, to understand how each system responds, it is necessary to consider its role in the context of the entire organism. Here, I have used the African cichlid fish Astatotilapia burtoni and its extraordinary phenotypic plasticity to investigate how animals respond to a change in social status from subordinate to dominant and attempted to integrate these multiple levels of biological response, as well as the roles of several candidate neuromodulators,. First, I have described how male A. burtoni become more aggressive and reproductive during their transition to dominance as well as increasing circulating levels of testosterone and estradiol and the histological organization of their testes. I then mapped the distribution of expression of two behaviorally relevant neuropeptides, arginine vasotocin and isotocin, and their respective receptors, throughout the A. burtoni brain, and found that they were highly expressed in several brain areas important for social behavior and decision-making. I then investigated the role of arginine vasotocin in social status and behavior via pharmacological manipulation and qPCR, showing the importance of arginine vasotocin in controlling the transition to dominance. Lastly, I investigated the role of aromatase, testosterone, and estradiol in male A. burtoni, both in stable dominant males and in males as they transition to dominance, using pharmacological manipulation and quantitative radioactive in situ hybridization, illustrating that estradiol synthesis during dominance is dependent on aromatase activity and necessary for aggressive behavior.