Tompkins Keith, Boswell Will, Du Kang, Lai Zhao, Lu Yuan, Morris Molly R
Department of Biological Sciences, Ohio University, Athens, OH, 45701, USA.
Institute for Molecular Life Sciences, Texas State University, San Marcos, TX, 78666, USA.
Fish Physiol Biochem. 2025 Jul 31;51(4):130. doi: 10.1007/s10695-025-01539-2.
Nuchal humps are morphological traits that occur among vertebrate species and have multiple functions. The emergence of nuchal humps in Xiphophorus multilineatus males maintained in the laboratory, a species that does not develop humps in the wild, provided a unique opportunity to explore the development and function of this trait. The current study investigated the tissue composition of the hump and analyzed the influence of rearing temperature and diet restriction on hump development. Through histological examination and gene expression profiling, our findings show that the hump is composed primarily of adipose tissue, which suggests a role in energy storage via fat deposition. Nuchal humps grew to a larger size in the cold environment (20 °C) than in the warm (25 °C), and the differential gene expression pattern between temperature treatments suggests increased fat deposition in the cold versus the warm environment. For example, the G0S2 gene, which inhibits lipid catabolism, is upregulated in the cold environment, and the WARS-1 gene, which leads to increased fat stores when under-expressed, is upregulated in the warm environment. The hypothesis that temperature influences hump development by stimulating shifts in fat metabolism is further supported by the finding that males from the warm environment used fat stores in the nuchal hump at a faster rate when placed on a restricted diet than males from the cold. The influence of temperature, diet, and potentially activity levels on fat deposition suggests X. multilineatus as an evolutionary animal model for gaining insights into the mechanisms involved in human obesity.
颈背隆肉是脊椎动物物种中出现的形态特征，具有多种功能。在实验室饲养的多线剑尾鱼雄性个体中出现了颈背隆肉，而该物种在野外不会发育出隆肉，这为探索这一特征的发育和功能提供了独特的机会。当前的研究调查了隆肉的组织组成，并分析了饲养温度和饮食限制对隆肉发育的影响。通过组织学检查和基因表达谱分析，我们的研究结果表明，隆肉主要由脂肪组织组成，这表明其通过脂肪沉积在能量储存中发挥作用。颈背隆肉在寒冷环境（20°C）中比在温暖环境（25°C）中长得更大，温度处理之间的差异基因表达模式表明，与温暖环境相比，寒冷环境中脂肪沉积增加。例如，抑制脂质分解代谢的G0S2基因在寒冷环境中上调，而表达不足时会导致脂肪储存增加的WARS-1基因在温暖环境中上调。当处于限制饮食时，来自温暖环境的雄性个体比来自寒冷环境的雄性个体更快地利用颈背隆肉中的脂肪储存，这一发现进一步支持了温度通过刺激脂肪代谢变化来影响隆肉发育的假说。温度、饮食以及潜在的活动水平对脂肪沉积的影响表明，多线剑尾鱼是一种进化动物模型，有助于深入了解人类肥胖所涉及的机制。
