温度对中华倒刺鲃不同生理生态性能的影响:驯化有益假说的验证

驯化有益假说(Beneficial acclimation hypothesis)认为生物表型的适应性变化会增强其在诱导这些变化产生的环境中的生理机能或适合度。然而,由于动物不同生理生态性能对环境驯化的响应可能不一致,那么,测试表型性状的选择对驯化有益假说的验证就尤为关键。为此,整合表征动物生存适合度的不同生理生态性能并探究其对环境驯化的响应模式就十分必要。以我国长江中上游广泛分布的中华倒刺鲃(Spinibarbus sinensis)为对象,考察了驯化温度(18℃、28℃)和测试温度(18℃、28℃)及其交互作用对该物种有氧运动能力和无氧运动能力的影响,为驯化有益假说等相关假说的验证提供参考。研究发现,中华倒刺鲃不同生理生态性能对温度驯化的响应存在差异:(1)驯化温度对表征中华倒刺鲃无氧运动能力的快速启动游泳无显著影响(除最大加速度外)(P>0.05),研究数据倾向于支持无益假说(No-advantage hypothesis);(2)驯化温度对表征中华倒刺鲃有氧运动能力的临界游泳速度(Critical swimming speed,Ucrit)和最大代谢率(Maximum metabolic rate, MMR)影响显著(P<0.05),18℃驯化-18℃测试下的Ucrit和MMR均优于28℃驯化-18℃测试下的Ucrit和MMR,结果部分支持驯化有益假说和冷有益假说(Cooler is better hypothesis);(3)驯化温度、测试温度、游泳速度对中华倒刺鲃的运动代谢率(Active metabolic rate,MO2)和单位距离能量消耗(The energetic cost of transport, COT)影响显著(P<0.05)。值得关注的是,当游泳速度小于30 cm/s时,驯化温度对MO2和COT无影响,结果支持无益假说;而当游泳速度大于30 cm/s时,在特定的流速下经过28℃驯化的中华倒刺鲃无论在28℃还是18℃的测试环境下MO2和COT均较低,结果倾向于支持热有益假说(Warmer is better hypothesis)。研究结果提示:驯化有益假说并不具有普遍性,热驯化相关假说的验证不仅受表型性状选择的影响,而且还与测试的环境选择压力有关。

Effects of temperature on different eco-physiological properties in Spinibarbus sinensis: testing the beneficial acclimation hypothesis

Traditionally, it has been assumed that all acclimation changes to the phenotype enhanced the performance of an individual organism in the environment in which those changes were induced(beneficial acclimation hypothesis, BAH). However, since the responses of different eco-physiological properties of animals to acclimation may be inconsistent, the phenotypes selected for testing are particularly critical for the verification of BAH. Thus, it is necessary to integrate different eco-physiological properties that characterize the fitness of the organism and to explore their response mode to acclimation. To verify the hypotheses(e.g. BAH) related to thermal acclimation, Spinibarbus sinensis, which is widely distributed in the middle and upper reaches of the Yangtze river in China, was taken as the object to investigate the effects of acclimation temperature(18℃ and 28℃) and test temperature(18℃ and 28℃), as well as their interactions on the aerobic and anaerobic swimming performance of this species. We confirmed that the responses of different eco-physiological properties in S. sinensis to temperature acclimation were not consistent.(1) In addition to maximum linear acceleration(Amax), acclimation temperature had no significant influence on maximum linear velocity(Vmax), latency time(TLatency) and escape distance during the first 120 ms after the stimulus(S120 ms) that characterize fast-start performance of S. sinensis(P>0.05). The data tend to support "no-advantage hypothesis".(2) Acclimation temperature had a significant effect on critical swimming speed(Ucrit) and maximum metabolic rate(MMR) that characterize aerobic swimming performance of S. sinensis(P<0.05). The Ucrit and MMR of the individuals acclimated to 18℃ and tested at 18℃ outperformed than those acclimated to 28℃ and tested at 18℃. The data tend to support the BAH as well as "cooler is better hypothesis" at least in part.(3) Both acclimation temperature, test temperature and water velocity had significant effects on active metabolic rate(MO2) and the energetic cost of transport(COT) in S. sinensis(P<0.05). Interestingly, acclimation temperature had no effect on MO2 and COT when the swimming speed was less than 30 cm/s, and in that case "no-advantage hypothesis" was supported. Whereas the MO2 and COT of the individuals acclimated to 28℃ were lower than those acclimated to 18℃ no matter the test temperature was 28℃ or 18℃ at a specific flow rate(greater than 30 cm/s), and in that case "warmer is better hypothesis" was supported. Overall, the data from our studies rejected the generality of the BAH. The results indicated that the verification of the BAH was not only influenced by the choice of phenotypic traits, but also strongly affected by the selection pressure of the test environment.