Institute of Aquaculture, Nha Trang University, Nha Trang, Viet Nam; Department of Biological Sciences, University of Bergen, Bergen, Norway. Electronic address: https://orcid.org/0000-0003-0520-7134.
Department of Biological Sciences, University of Bergen, Bergen, Norway.
Gen Comp Endocrinol. 2021 Apr 1;304:113719. doi: 10.1016/j.ygcen.2021.113719. Epub 2021 Jan 19.
The clown anemonefish (Amphiprion ocellaris) is a common model species in studies assessing the impact of climate changes on tropical coral fish physiology, metabolism, growth, and stress. However, the basic endocrine principles for the control of food intake and energy homeostasis, under normal and elevated sea temperatures, in this species remain unknown. In this work, we studied food intake and growth in clown anemonefish reared at different temperatures and with different food availability. We also analyzed expression of genes in the melanocortin system, which is believed to be involved in the control of appetite and feeding behavior. These were two paralogues of pomc: pomca and pomcb; two paralogs of agrp: agrp1 and agrp2; and one mc4r-like. Groups of juvenile clown anemonefish were exposed to four experimental treatments combining (orthogonal design) two rearing temperatures: 28 °C (T28; normal) and 32 °C (T32; high) and two feeding regimes: one (1 M; 08:00) or three (3 M; 08:00, 12:00, 15:00) meals per day, fed to satiety by hand. The results showed that high temperature (T32) did not affect the average growth rate but induced a stronger asymmetrical individual body weight of the fish within the population (tank). Lower feeding frequency (1 M) resulted in lower growth rates at both rearing temperatures. Fish reared at high temperature had higher total daily food intake, which correlated with a lower expression of pomca, supporting an anorexigenic role of this gene. High temperature combined with restricted feeding induced higher agrp1 levels and resulted in a higher food intake in the morning meal compared to the control. This supports an orexigenic role for agrp1. mRNA levels of agrp2 responded differently from agrp1, supporting different roles for the paralogues. Levels of mc4r-like inversely correlated with fish body weight, indicating a possible size/stage dependence of gene expression. In conclusion, our results indicate that the melanocortin system is involved in adjusting appetite and food intake of clown anemonefish in response to elevated temperature and low food availability.
小丑鱼（Amphiprion ocellaris）是研究气候变化对热带珊瑚鱼生理、代谢、生长和应激影响的常用模式生物。然而，在这种物种中，控制食物摄入和能量平衡的基本内分泌原理，在正常和升高的海温下仍然未知。在这项工作中，我们研究了在不同温度和不同食物可利用性下饲养的小丑鱼的食物摄入和生长情况。我们还分析了黑色素皮质素系统中基因的表达，该系统被认为参与了食欲和摄食行为的控制。这些是 pomc 的两个旁系同源物：pomca 和 pomcb；agrp 的两个旁系同源物：agrp1 和 agrp2；和一个 mc4r 样。一群幼年小丑鱼暴露于四个实验处理中，这些处理组合了（正交设计）两个饲养温度：28°C（T28；正常）和 32°C（T32；高温）和两种喂养制度：每天一次（1M；08:00）或三次（3M；08:00、12:00、15:00）用餐，通过手动喂食至饱食。结果表明，高温（T32）不会影响平均生长率，但会在群体（缸）内诱导更强的鱼个体体重不对称性。较低的喂养频率（1M）会导致两种饲养温度下的生长率降低。在高温下饲养的鱼的总日食物摄入量更高，这与该基因的表达降低有关，支持该基因具有厌食作用。高温与限制喂养相结合会诱导更高的 agrp1 水平，并导致与对照相比，早餐时的食物摄入量更高。这支持 agrp1 具有促进食欲的作用。agrp2 的 mRNA 水平与 agrp1 不同，支持其旁系同源物具有不同的作用。mc4r 样的水平与鱼体重呈反比，表明基因表达可能与鱼的大小/阶段有关。总之，我们的结果表明，黑色素皮质素系统参与调节小丑鱼对高温和低食物可利用性的食欲和食物摄入。
