墨西哥丽脂鲤洞穴型（Astyanax mexicanus）的口腔味觉偏好与食物处理行为

文献信息

中文摘要

自1936年被发现以来，墨西哥丽脂鲤（Astyanax mexicanus）的洞穴型已成为补偿性适应研究的一个有前景的模型。视觉的丧失驱动了洞穴型感觉系统的适应性进化。对味觉系统的研究主要集中在味蕾的形态和分布上，但该系统的功能方面仍不清楚。在本研究中，首次鉴定了A. mexicanus洞穴型的口腔味觉偏好。通过行为学测定发现，21种蛋白质源性L-氨基酸中超过一半、18种有机酸中超过三分之一，以及四种基本味觉物质中几乎全部，要么被 indifferent（无反应），要么被排斥。这些发现与基于洞穴型机会主义摄食模式的预期不一致。此外，最适口物质——马来酸——的阈值浓度处于表层鱼类物种中常见的范围内。总之，没有证据表明洞穴型发生了口腔味觉感知的补偿性改善。洞穴型通常只需一次抓取就足以吞咽或不可逆地拒绝所提供的颗粒。相对较长的保留时间，尤其是对适口颗粒，是食物处理行为的另一个特征。在吞咽之前，洞穴型保留颗粒的时间长达八到九倍，无论其味觉质量如何。

英文摘要

Since its discovery in 1936, the cave morph of the Mexican tetra, Astyanax mexicanus, has become a promising model for studies of compensatory adaptation. The loss of vision has driven the adaptive evolution of sensory systems in the cave morph. Studies of the gustatory system have mainly focused on the morphology and distribution of taste buds, but the functional aspects of this system remain unknown. In the present study, oral taste preferences of the cave morph of A. mexicanus were identified for the first time. Using a behavioural assay, it was found that more than half of the 21 proteinogenic L-amino acids and more than one-third of the 18 organic acids, as well as nearly all of the four basic taste substances, were either indifferent or repulsive. These findings are not consistent with expectations based on the opportunistic feeding mode of the cave morph. In addition, the threshold concentration of the most palatable substance, maleic acid, is within the range commonly found in epigean fish species. In summary, there is no evidence to suggest that compensatory improvement in oral taste perception has occurred in the cave morph. A single grasp is often sufficient for the cave morph to swallow or irreversibly reject an offered pellet. The relatively long retention time, especially for palatable pellets, is another characteristic of food-handling behaviour. Before swallowing, the cave morph retains pellets for up to eight to nine times longer, regardless of their taste quality.