Interspecific differences and ecological correlations of energy metabolism traits in freshwater fishes

Abstract

Metabolic energy fuels all biological processes, and thus, energy metabolism is vitally important for organisms. It has been suggested that interspecific variation in physiological functions is associated with the energetic metabolism of organisms, which varies considerably due to selection, adaptation and evolution. Thus, the present study aimed to clarify the relationship between the interspecific diversification of maintenance energy expenditure and two forms of anaerobic capacity (in terms of exercise and hypoxia tolerance) in freshwater fishes. Moreover, in the context of environmental adaptation, we hypothesized that selection for increased locomotor performance in species with a fast‐flow lifestyle favours a high aerobic and anaerobic capacity and, consequently, a high maintenance metabolism, whereas selection for strong hypoxia tolerance in species with a slow‐flow lifestyle favours a reduced maintenance metabolism and a reduced aerobic capacity. We examined these topics among 30 species of freshwater fish with different lifestyles based on the flow regimes of their habitats (fast, intermediate and slow flow). The resting metabolic rate of each species was measured, and then, the fish were subjected to two treatments: (a) exercise to exhaustion, after which we measured the maximum metabolic rate, excess post‐exercise oxygen consumption and metabolic recovery rate; and (b) hypoxia to the point of loss of equilibrium (LOE), after which we measured the metabolic response to recovery from hypoxia, including the peak metabolic rate (PMRh) and the excess post‐hypoxia oxygen consumption (EPOCh). We found that the resting metabolic rate was positively correlated with both the aerobic and anaerobic capacity of the fishes and that species from fast‐flow habitats have higher aerobic and anaerobic capacity with concomitantly increased resting metabolism. However, neither EPOCh nor LOE was correlated with resting metabolic rate. In summary, we suggest that selection for increased aerobic and anaerobic capacity to facilitate the demands of exercise has occurred in fast‐flow species, that selection for hypoxia tolerance may have favoured a reduction in this capacity in intermediate and slow‐flow species, and that specialized adaptations (such as flexibility in gill morphology and altered metabolic pathways) play important roles in hypoxia tolerance in some species. A free Plain Language Summary can be found within the Supporting Information of this article.

Size-related effects and the influence of metabolic traits and morphology on swimming performance in fish

“…2019 ) and, therefore, the energy budget of species plays a key role in many interactions with the physiology and ecology of organisms ( Killen et al. 2010 ; Pang et al. 2019 ).…”

“…More recently, this hypothesis has been tested in ectotherms and suggests that selection for a high aerobic capacity to maintain intense and sustained activity is functionally supported by an increase in metabolic costs of maintenance, thereby increasing SMR ( Killen et al. 2016 ; Pang et al. 2019 ).…”

Effects of short-term fasting on spontaneous activity and excess post-exercise oxygen consumption in four juvenile fish species with different foraging strategies

“…The relationship between the post-exercise O 2 (Y, mg O 2 kg −1 h −1 ) and the time after exercise (X, min) is described by the following equation: where a is the pre-exercise O 2 , b is the O 2 increment, and c is the recovery rate. A high c value indicates a fast rate of recovery from exhaustive exercise ( Pang et al, 2019 ).…”

“…where a is the pre-exercise M ð †ÞO 2 , b is the M ð †ÞO 2 increment, and c is the recovery rate. A high c value indicates a fast rate of recovery from exhaustive exercise (Pang et al, 2019). This study complied with the current law of the country in which it was performed and was approved by the Animal Care and Use Committee of the Key Laboratory of Animal Biology of Chongqing ( permit number Zhao-20,151,010-01).…”

One size does not fit all: inter- and intraspecific variation in the swimming performance of contrasting freshwater fish

“…River fish communities consist of species with different body shapes, physiological traits and swimming modes that define their realized niches ( Willis et al ., 2005 ; Poff and Allan, 1995 ; Montaña et al , 2014 ; Pang et al ., 2020 ). Additionally, individuals of the same species can show substantial trait variation at the population level due to adaptation to local environmental conditions (e.g.…”