Institute of Science and Environment, University of Saint Joseph, Macao.
Horm Behav. 2021 Jun;132:104991. doi: 10.1016/j.yhbeh.2021.104991. Epub 2021 May 10.
The role of hormones as modulators of aggressive behavior in fish remains poorly understood. Androgens and corticosteroids, in particular, have been associated with aggressive behavior in fish but it is still not clear if animals adjust the secretion of these hormones to regulate behavior during ongoing fights, in response to fight outcomes in order to adjust aggressive behavior in subsequent fights, or both. With its stereotyped displays and high aggression levels, the Siamese fighting fish Betta splendens is an excellent model to investigate this question. Here, we compared the behavioral and endocrine response of male B. splendens to fights where there is no winner or loser by presenting them with a size-matched live interacting conspecific behind a transparent partition or with a mirror image. The aggressive response started with threat displays that were overall similar in frequency and duration towards both types of stimuli. Fights transitioned to overt attacks and interacting with a live conspecific elicited a higher frequency of attempted bites and head hits, as compared with the mirror image. There was a pronounced increase in plasma androgens (11-ketotestosterone and testosterone) and corticosteroids (cortisol) levels in response to the aggression challenge, independent of stimulus type. Post-fight intra-group levels of these hormones did not correlate with measures of physical activity or aggressive behavior. A linear discriminant analysis including all behavioral and endocrine data was a poor classifier of fish from the conspecific and mirror trials, showing that overall the behavioral and endocrine response to mirror images and conspecifics was similar. The results show that fight resolution is not necessary to induce an evident increase in peripheral levels of androgens and corticosteroids in B. splendens. However, the function of these hormones during present and future aggressive contests remains to be clarified.
激素作为鱼类攻击性行为调节剂的作用仍知之甚少。雄激素和皮质甾醇，特别是与鱼类的攻击性行为有关，但仍不清楚动物是否会调整这些激素的分泌，以在持续的战斗中调节行为，对战斗结果作出反应，以便在随后的战斗中调整攻击性行为，或者两者兼而有之。暹罗斗鱼（Betta splendens）因其刻板的表现和高度的攻击性，是研究这个问题的绝佳模型。在这里，我们通过向雄性暹罗斗鱼展示一个大小匹配的活体互动同种个体在透明隔板后面，或镜像，来比较它们在没有胜负的战斗中的行为和内分泌反应。攻击反应以威胁表现开始，无论是面对活体同种个体还是镜像，其威胁表现的频率和持续时间总体上相似。战斗过渡到明显的攻击，与活体同种个体互动会引起更高频率的试图咬和头部撞击，与镜像相比。无论刺激类型如何，血浆雄激素（11-酮睾酮和睾酮）和皮质甾醇（皮质醇）水平都会因攻击挑战而明显升高。战斗后，这些激素的组内水平与身体活动或攻击性行为的测量值没有相关性。包括所有行为和内分泌数据的线性判别分析并不能很好地区分来自同种和镜像试验的鱼类，表明总体而言，对镜像和同种个体的行为和内分泌反应相似。研究结果表明，战斗的解决并不需要引起暹罗斗鱼外周雄激素和皮质甾醇水平的明显增加。然而，这些激素在当前和未来的攻击性行为中的作用仍有待阐明。
