Limited aerobic scope(AS)during digestion might be the main constraint on the performance of bodily functions in water-breathing animals.Thus,investigating the postprandial changes in various physiological functions and determining the existence of a shared common pattern because of possible dependence on residual AS during digestion in freshwaterfish species are very important in conservation physiology.All species from slow-flow habitats showed impaired swimming speed while digesting,whereas all species from fast-flow habitats showed strong swimming performance,which was unchanged while digesting.Only two species from slow-flow habitats showed impaired heat tolerance during digestion,suggesting that whether oxygen limitation is involved in the heat tolerance process is species-specific.Three species from slow-or intermediate-flow habitats showed impaired hypoxia tolerance during digestion because feeding metabolism cannot cease completely under hypoxia.Overall,there was no common pattern in postprandial changes in different physiological functions because:(1)the digestion process was suppressed under oxygen-limiting conditions,(2)the residual AS decreased during digestion,and(3)performance was related to residual AS,while digestion was context-dependent and species-specific.However,digestion generally showed a stronger effect on bodily functions in species from slow-flow habitats,whereas it showed no impairment infishes from fast-flow habitats.Nevertheless,the postprandial change in physiological functions varies with habitat,possibly due to divergent selective pressure on such functions.More importantly,the present study suggests that a precise prediction of how freshwaterfish populations will respond to global climate change needs to incorporate data from postprandialfishes.
Yongfei ZHANGYulian LUOKeren HUANGQianying LIUCheng FUXu PANGShijian FU
