不同捕食者暴露对鲫幼鱼行为、运动和形态特征的影响

自然界中鱼类的捕食者种类繁多，为验证猎物鱼针对不同捕食者是否会做出相异的反捕食策略选择，选取鲫（Carassius auratus）幼鱼为猎物鱼，乌鳢（Channa argus）和胡子鲶（Clarias fuscus）为捕食者，将鲫幼鱼分别暴露于空白（对照）、乌鳢、胡子鲶和双捕食者（同时存在乌鳢和胡子鲶）环境中持续2个月，随后考查不同组鲫幼鱼的生长、行为特征、形态和运动能力等指标之间的差异。结果表明：经过2个月的捕食胁迫处理，鲫幼鱼的自发运动、隐蔽场所利用率和勇敢性等行为指标在4个组之间均未表现出显著性差异。相比对照组，乌鳢、胡子鲶和双捕食者暴露组鲫幼鱼的快速启动反应时滞显著缩短（P<0.05）；但所有处理组中仅乌鳢暴露组鲫幼鱼的快速启动120ms移动距离（S_120ms）和体高（BD）显著高于对照组（P<0.05）。另外鲫幼鱼的临界游泳速度（U_crit）和活跃代谢率（M_O2active）在各组之间也未表现出显著差异。乌鳢暴露组鲫幼鱼快速启动能力的提升可能与形态上体高的提高有关；另外相比临界游泳能力，快速启动能力可能在鱼类逃避捕食者过程中更为关键；鲫幼鱼表现出对乌鳢的反应最为明显，可能与乌鳢口裂较大，给鲫幼鱼带来的威胁更大有关。整体而言，应对捕食胁迫时，鲫幼鱼仅表现出形态和快速启动能力的反捕食响应，其行为特征的保守性可能是对生长作出的妥协，这对于鱼类适应生境中长期存在的捕食胁迫十分关键。

Effects of different predators exposure on behavior, locomotion, and morphological traits in juvenile crucian carp

Different kinds of predators of fish species present in nature. In order to investigate whether the prey fish would show specialized anti-predator responses to different predators, in this study, the juvenile crucian carp (Carassius auratus) was selected as prey, and both snake head fish (Channa argus) and catfish (Clarias fuscus) were selected as predators, the crucian carps were exposed to blank (control), snake head fish, catfish and double predators respectively for two months. Then the differences in growth, behavioral traits, morphology, and locomotion performance among different groups were determined. No significant difference in spontaneous activity, utilization of shelter and boldness in crucian carp was found among different groups. The crucian carp from snake head fish, catfish and double predators exposed groups all showed significantly shorter fast-start response latency compared to that of the control group (P<0.05). However, only the fast-start distance moved in 120 ms (S_120ms) and body depth (BD) of snake head fish exposed group was significantly higher than that of the control group (P<0.05). Additionally, no significant difference was found in critical swimming speed (U_crit) and active metabolic rate (M_O2active) among different groups. The improvement of fast-start performance in the crucian carp from snake head fish exposed group may be related to the increase in body depth. Additionally, the fast-start performance may be more important for escaping from predators compared to critical swimming performance. The juvenile crucian carp response to snake head fish more obvious may be because that the snake head fish have larger oral fissure, and bring more serious threat to crucian carp. On the whole, juvenile crucian carp only showed the changed morphology and fast-start performance as the response to predation stress, its behavioral traits maintained no change, which might as a compromise to growth. It is very important for fish species to adapt to the long-term predation pressure existed in habitats.