Joyce Brendan J, Brown Grant E
Department of Biology, Concordia University, Montreal, Quebec, Canada.
Curr Zool. 2022 Nov 2;69(6):738-746. doi: 10.1093/cz/zoac086. eCollection 2023 Dec.
Neuroplasticity enables teleosts to promote or downregulate the growth of their brains regionally. To compensate for the effects of predation pressure, teleosts may alter their brain morphology and behavioral responses to mitigate its impact on individual fitness. High-predation environments often promote specific patterns of brain growth and produce bolder and more proactive populations. Owing to the expense of maintaining neural tissue, relative size indicates the regions most relied upon. In northern redbelly dace , as little as 2 weeks of elevated predation pressure, resulted in increased investment in their olfactory bulbs and optic tecta, while the imposition of captivity produced smaller, less symmetric hypothalami. Taken together, these results suggest that an individual could potentially become better able to detect a threat, and simultaneously less inclined to react to it, making the impact of either change in isolation is difficult to discern. Here, we compared interindividual variation in gross brain morphology, risk-taking tactics in a novel arena (shy-bold personality), and responding to olfactory cues (proactive/reactive stress-coping style). We hypothesized that olfactory investment would positively correlate with response intensity to predator cue concentration and respond across a wider range of cue concentrations, while hypothalamus size would correlate with shyness and reactivity. Exposure to heightened risk produced more bold/proactive individuals, with larger olfactory bulbs and smaller hypothalami. However, the direction of the correlation between hypothalamus size and behavior varied by treatment, and olfactory investment only corresponded with response intensity amongst proactive individuals. Our findings illustrate the potential pitfalls of relating gross brain morphology to complex behavior and suggest that stress-coping style is a relevant consideration in future studies.
神经可塑性使硬骨鱼能够在区域上促进或下调其大脑的生长。为了补偿捕食压力的影响，硬骨鱼可能会改变其大脑形态和行为反应，以减轻其对个体适应性的影响。高捕食环境通常会促进特定的大脑生长模式，并产生更大胆、更主动的种群。由于维持神经组织的成本，相对大小表明了最依赖的区域。在北方红腹雅罗鱼中，仅2周的高捕食压力就导致其嗅球和视顶盖的投资增加，而圈养则导致下丘脑变小且对称性降低。综合来看，这些结果表明，个体可能会变得更善于检测威胁，同时对威胁的反应倾向降低，因此很难辨别单独一种变化的影响。在这里，我们比较了大脑总体形态的个体间差异、在新环境中的冒险策略（害羞-大胆性格）以及对嗅觉线索的反应（主动/被动应激应对方式）。我们假设嗅觉投资与对捕食者线索浓度的反应强度呈正相关，并且在更广泛的线索浓度范围内有反应，而下丘脑大小与害羞和反应性相关。暴露于更高风险会产生更大胆/更主动的个体，其嗅球更大而下丘脑更小。然而，下丘脑大小与行为之间的相关方向因处理方式而异，并且嗅觉投资仅与主动个体中的反应强度相对应。我们的研究结果说明了将大脑总体形态与复杂行为联系起来的潜在陷阱，并表明应激应对方式是未来研究中一个相关的考虑因素。
