Sun Chun-Yan, Fu Shi-Jian, Zeng Ling-Qing
Laboratory of Evolutionary Physiology and Behaviour, College of Life Sciences, Chongqing Normal University, Key Laboratory of Animal Biology of Chongqing, Room 127, Yifu Building, Chongqing, 401331, People's Republic of China.
J Comp Physiol B. 2023 Jan;193(1):95-108. doi: 10.1007/s00360-022-01467-0. Epub 2022 Nov 10.
Growth and energy metabolism are highly flexible in fish species in response to food availability, and these two traits depend to some extent on the social rearing environment (e.g., isolated vs. group rearing). Currently, how social rearing environments influence flexibility in metabolic rate of fish and their ecological consequences (e.g., somatic growth) remain largely unknown. Here, we investigated how social isolation (i.e., group-reared vs. isolation-reared) and food availability (i.e., high vs. low) affect metabolic rates, growth and their correlations in a group-living fish, grass carp (Ctenopharyngodon idella), which were subjected to a 4-week growth experiment. The metabolic rates (e.g., standard metabolic rate, SMR; maximum metabolic rate, MMR; aerobic scope, AS = MMR-SMR) and morphology (e.g., body mass and length) of the fish in four treatments were measured at the beginning and end of the growth experiment, and then the growth parameters (e.g., food intake, FI; feeding efficiency, FE; and specific growth rate, SGR) were also obtained. We found that social isolation did impair growth of fish with individuals showing a lower SGR compared to those group-reared fish irrespective of food availability. However, the growth advantage of group-reared fish under two food availabilities did not result from their FIs or FEs. Metabolic rates (i.e., SMR) seemed to decrease in response to social isolation, but increased greater when fish were reared at high food ration. These shifts in metabolic rates were positively linked with individual differences in somatic growth; individuals who increased metabolic rates more grew faster, while those who increased their metabolic rates less or even reduced had a lower growth, but these links were independent on both social isolation and food ration. These results suggested that social isolation can inhibit the growth of individual fish, but not the AS. Flexibility in metabolic rates could confer a growth advantage under changing food availability, but the links between variation in energy metabolism and growth were not altered by social deprivation. Our study demonstrates the importance of metabolic plasticity accounting for inter-individual difference in growth performance under the challenges of changing food resource.
鱼类的生长和能量代谢会根据食物供应情况进行高度灵活的调整，并且这两个特征在一定程度上取决于社会饲养环境（例如，单独饲养与群体饲养）。目前，社会饲养环境如何影响鱼类代谢率的灵活性及其生态后果（例如，体细胞生长）在很大程度上仍不清楚。在此，我们研究了社会隔离（即群体饲养与单独饲养）和食物供应（即高与低）如何影响一种群居鱼类——草鱼（Ctenopharyngodon idella）的代谢率、生长及其相关性，这些草鱼接受了为期4周的生长实验。在生长实验开始和结束时测量了四种处理方式下鱼类的代谢率（例如，标准代谢率，SMR；最大代谢率，MMR；有氧范围，AS = MMR - SMR）和形态（例如，体重和体长），然后还获得了生长参数（例如，食物摄入量，FI；摄食效率，FE；以及特定生长率，SGR）。我们发现，无论食物供应情况如何，社会隔离确实会损害鱼类的生长，与群体饲养的鱼类相比，单独饲养的个体表现出较低的特定生长率。然而，在两种食物供应情况下，群体饲养鱼类的生长优势并非源于它们的食物摄入量或摄食效率。代谢率（即标准代谢率）似乎会因社会隔离而降低，但当鱼类以高食物配给饲养时，代谢率增加得更多。这些代谢率的变化与体细胞生长的个体差异呈正相关；代谢率增加更多的个体生长得更快，而那些代谢率增加较少甚至降低的个体生长较慢，但这些联系与社会隔离和食物配给均无关。这些结果表明，社会隔离会抑制个体鱼类的生长，但不会影响有氧范围。在食物供应变化的情况下，代谢率的灵活性可以赋予生长优势，但能量代谢变化与生长之间的联系不会因社会剥夺而改变。我们的研究证明了代谢可塑性在应对食物资源变化挑战时对个体生长性能差异的重要性。
