Neuroscience Program, University of Illinois, Urbana-Champaign, IL, USA.
Beckman Institute for Advanced Science and Technology, University of Illinois, Urbana-Champaign, IL, USA.
Horm Behav. 2022 Sep;145:105239. doi: 10.1016/j.yhbeh.2022.105239. Epub 2022 Aug 1.
Many fish species exhibit natural sex change as part of their life, providing unique opportunities to study sexually-differentiated social behaviors and their plasticity. Past research has shown that behavioral sex change in the female-to-male (protogynous) direction occurs rapidly and well before gonadal sex change. However, little is known about the timecourse of behavioral sex change in male-to-female (protandrous) sex-changing species, limiting our ability to compare patterns of behavioral sex change across species and identify conserved or divergent underlying mechanisms. Using the protandrous sex changing anemonefish Amphiprion ocellaris, we assessed behavior (aggression and parental care) and hormones (estradiol and 11-ketotestosterone) in fish over six months of sex change, and compared those fish against their non-changing partners as well as control males and females. Contrary to expectations, we found that sex-changing fish displayed behavior that was persistently male-like, and that their behavior did not become progressively female-like as sex change progressed. Hormones shifted to an intermediate profile between males and females and remained stable until gonads changed. These results support a new perspective that the timecourse for protandrous sex change in anemonefish is completely distinct from other well-established models, such that behavioral sex change does not occur until after gonadal sex change is complete, and that sex-changing fish have a stable and unique behavioral and hormonal phenotype that is distinct from a male-typical or female-typical phenotype. The results also identify aspects of sex change that may fundamentally differ between protandrous and protogynous modes, motivating further research into these remarkable examples of phenotypic plasticity.
许多鱼类在其生命周期中表现出自然的性别转变，这为研究性分化的社会行为及其可塑性提供了独特的机会。过去的研究表明，雌性到雄性（雌雄同体）方向的行为性别转变发生得很快，而且远在性腺性别转变之前。然而，对于雄性到雌性（雌雄同体）性别转变物种的行为性别转变的时间进程知之甚少，这限制了我们比较物种间行为性别转变的模式并确定保守或不同的潜在机制的能力。我们使用雌雄同体的海葵鱼 Amphiprion ocellaris，评估了在六个月的性别转变过程中鱼的行为（攻击性和亲代照顾）和激素（雌二醇和 11-酮睾酮），并将这些鱼与它们不变的伴侣以及对照雄性和雌性进行了比较。与预期相反，我们发现变性鱼表现出持续的雄性行为，并且随着性别转变的进行，它们的行为并没有逐渐变得雌性化。激素转变为介于雄性和雌性之间的中间模式，并保持稳定，直到性腺发生变化。这些结果支持了一种新的观点，即海葵鱼的雄性到雌性的性别转变时间进程与其他成熟的模型完全不同，以至于行为性别转变直到性腺性别转变完成后才发生，而且变性鱼具有稳定而独特的行为和激素表型，与典型的雄性或雌性表型不同。这些结果还确定了性别转变在雌雄同体和雌雄同体模式之间可能存在根本差异的方面，这激发了对这些显著的表型可塑性的进一步研究。
