DISSERTATION RESEARCH: Androgen regulation of territorial male-typical behavior and neuropeptide gene expression during socially-induced sex and role change in a coral reef fish

对当前环境或社会状况的反应和适应能力，在很大程度上取决于做出行为、生理和神经变化的灵活性。人们非常感兴趣的一个领域是大脑在应对新挑战时的可塑性。这种能力的一个最好的例子是在能够从雌性转变为雄性或从雄性转变为雌性的鱼类身上看到的，无论是行为还是表型。当种群的变化、雄性或雌性的丧失增加了通过变化而繁殖的能力时，就会发生这种情况。在具有社会控制的性别变化和/或角色变化的物种中，大脑感知到社会环境的变化，这表明它有利于这些变化，因此是“允许的”。在一种加勒比海珊瑚鱼中观察到了这一点，这是一种具有类似LEK的交配系统的加勒比海珊瑚鱼，在这种交配系统中，领土末端阶段(T-TP)的雄性保卫产卵区域，以获得雌性并与多个雌性繁殖。将一只T-TP雄鱼从产卵区域移出会创造一个允许的环境，导致最大的雌性或最大的非领地雄性角色改变，无论是初始阶段(IP)雄性还是非领地-终末阶段(NT-TP)雄性。这项研究将考察雄激素在应对不断变化的社会影响时所起的作用，以促进行为和表型变化。这些类型的研究很重要，因为它们有能力证明社交互动的限制，以及大脑在限制消失或环境发生重大变化时改变的能力。在将蓝头鲸T-TP雄性从其领地移走后，在几分钟到几小时内，最大的雌性、IP雄性或NT-TP雄性的大脑发生变化，引发T-TP雄性的典型行为，如向雌性求爱和针对其他雄性的争斗行为。大脑的变化也会激活下丘脑-垂体-性腺(HPG)轴，导致女性卵巢或IP男性睾丸转变为TP男性睾丸。雄性激素的产生，特别是11kT，在性腺转变过程中，女性和从属男性在性别和角色变化期间都会增加。虽然之前的研究表明，11kt的增加对于行为变化并不是必要的，但其他观察表明，这种雄激素可能起着重要作用。神经肽血管催产素(哺乳动物中的加压素的同系物)似乎与早期的行为变化有关。然而，11kT的存在是否会导致更早的行为改变，并增加T-TP男性典型行为的表现？NT-TP男性的基线水平高于IP男性和女性，并且似乎更快地过渡到T-TP男性的角色。11kt是否有助于更快地进行角色转换？研究人员假设，11kT促进了T-TP期男性在允许的社会条件下的典型行为和基因表达谱。使用捕获/标记和释放/重捕获方法、通过性腺切除和11kt植入进行的激素操作、标记个体的行为观察、11kt血清检测和qRT-PCR基因表达分析相结合的方法，本研究将检验：1)在允许的条件下，经历性别和角色改变的女性、IP男性和NT-TP男性在T-TP男性典型行为的时间、频率和持续时间方面是否存在显著差异；2)性腺的存在影响T-TP男性典型行为和血管催产素系统和另外两个神经肽系统，Kisspeptin和促性腺激素释放激素，在性别和角色转变期间的基因表达3)11kT促进T-TP雄性典型行为和这些神经肽系统在性别和角色变化过程中的基因表达。这项研究将有助于确定11kt是否为竞争成为地区表型的个体提供了优势。

The ability to respond and adapt to current environmental or social condition, depends to a large extent of the flexibility to make behavioral, physiological and neurological changes. An area of great interest is the plasticity of the brain to change in response to new challenges. One of the greatest examples of this ability is seen in fish that are capable of switching from female-to-male or male-to-female either behavioral or phenotypically. This occurs when changes in the population, loss of males or females increase the ability to reproduce by changing. In species with socially-controlled sex change and/or role change, the brain perceives alterations in the social environment that indicate it is favorable for these changes and therefore "permissive". This is observed in the bluehead wrasse (Thalassoma bifasciatum), a Caribbean coral reef fish with a lek-like mating system in which territorial-terminal phase (T-TP) males defend spawning territories for access to females and breed with multiple females. Removal of a T-TP male from a spawning territory creates a permissive environment that induces sex change in the largest female or male role change in the largest non-territorial male, either an initial phase (IP) male or non-territorial-terminal phase (NT-TP) male. This research will examine the role androgen hormones in response to changing social influences to promote behavioral and phenotypic changes. These types of studies are important as they have the ability to demonstrate the constraint of social interactions and the brains ability to change to when constraints are left or there are major changes in the environment. Within minutes-to-hours of removing a bluehead wrasse T-TP male from its territory, changes in the brain of the largest female, IP male, or NT-TP male induce T-TP male-typical behaviors, such as courtship of females and agonistic behavior directed at other males. Changes in the brain also activate the hypothalamo-pituitary-gonadal (HPG) axis, causing transformation of female ovaries or IP male testes into TP male testes. Androgen production, particularly of 11KT, rises during gonadal transformation in both females and subordinate males during sex and role change. While previous studies show 11KT increases are not necessary for behavioral changes, other observations nevertheless suggest this androgen may play an important role. The neuropeptide vasotocin (homologue of vasopressin in mammals) appears responsible for early behavioral changes. However, could the presence of 11KT induce earlier onset of behavioral changes and increase the display of T-TP male-typical behaviors? NT-TP males have higher baseline levels of 11KT than IP males and females and appear to transition into the role of T-TP male faster. Is 11KT responsible for faster role change? The researchers hypothesize that 11KT promotes behaviors and gene expression profiles typical of T-TP phase males under permissive social conditions. Using a combination of capture/tag-and-release/recapture approaches, hormonal manipulations via gonadectomy and 11KT implantation, behavioral observations of tagged individuals, 11KT serum assays, and gene expression analysis via qRT-PCR, this study will test whether 1) significant differences exist in the timing, frequency, and duration of T-TP male-typical behaviors among females, IP males, and NT-TP males undergoing sex and role change under permissive conditions, 2) gonadal presence affects T-TP male-typical behaviors and gene expression of the vasotocin system and two other neuropeptide systems, kisspeptin and gonadotropin-releasing hormone, during sex and role change, and 3) 11KT promotes T-TP male-typical behaviors and gene expression of these neuropeptide systems during sex and role change. This study will help determine whether 11KT confers an advantage for individuals competing to become the territorial phenotype