Plasticity, repeatability, and phenotypic correlations of aerobic metabolic traits in a small estuarine fish

Abstract

14 15 SUMMARY STATEMENT 16Aerobic metabolism of an ecologically dominant estuarine fish is influenced by acclimation to 17 environmental changes without altering trait repeatability. Furthermore, specific metabolic traits 18 are phenotypically correlated. 19 20 ABSTRACT 21Standard metabolic rate (SMR), maximum metabolic rate (MMR), absolute aerobic scope 22 (AAS), and critical oxygen tension (Pcrit) were determined for the Gulf killifish, Fundulus 23 grandis, an ecologically dominant estuarine fish, acclimated to lowered salinity, elevated 24 temperature, and lowered oxygen concentration. Acclimation to low salinity resulted in a small, 25 but significant, elevation of Pcrit; acclimation to elevated temperature increased SMR, MMR, 26 AAS, and Pcrit; acclimation to low oxygen led to a small increase in SMR, but substantial 27 decreases in MMR, AAS, and Pcrit. Variation in these metabolic traits among individuals was 28 consistent and repeatable when measured during multiple control exposures over seven months. 29Trait repeatability was unaffected by acclimation condition suggesting that repeatability of these 30 traits is not context dependent. There were significant phenotypic correlations between specific 31 metabolic traits: SMR was positively correlated with MMR and Pcrit; MMR was positively 32 correlated with AAS; and AAS was negatively correlated with Pcrit. In general, within-individual 33 variation contributed more than among-individual variation to these phenotypic correlations. The 34 effects of acclimation on these traits demonstrate that aerobic metabolism is plastic and 35 influenced by the conditions experienced by these fish in the dynamic habitats in which they 36 occur; however, the repeatability of these traits and the correlations among them suggest that 37 these traits change in ways that maintains the rank order of performance among individuals 38 across a range of environmental variation. 39 40 Keywords: acclimation, aerobic metabolism, hypoxia, individual variation, phenotypic 41 correlations, repeatability 42 List of symbols and abbreviations 43 a.s.: air saturation 44 AAS: Absolute aerobic scope 45 BC: Bayou Cumbest 46 BH: Bayou Heron 47 DO: dissolved oxygen 48 GBNERR: Grand Bay National Estuarine Research Reserve 49 Mb: body mass 50 MMR: Maximum metabolic rate 51 MO2: rate of oxygen consumption 52 Pcrit: critical oxygen tension 53 RMR: routine metabolic rate 54 Radj: adjusted repeatability 55 rp: phenotypic correlation 56 re: within-individual correlation 57 rind: among-individual correlation 58 SMR: standard metabolic rate 59 60Elucidating the causes and consequences of variation in energy metabolism is a central goal of 62 animal physiology and ecology (Schmidt-Nielsen, 1997;Brown et al., 2004). In particular, there 63 is considerable interest in the effects of changes in the abiotic environment on the intensity of 64 energy metabolism, an interest that has been heightened by the rate and extent of contemporary 65 alterations in climate and other environmental variables brought about by...

Interindividual plasticity in metabolic and thermal tolerance traits from populations subjected to recent anthropogenic heating

“…In comparison to WAM and CaM, CT max had little interindividual variation (less than 3% and less than 1% for 12°C and 28°C, respectively). This interindividual variation for metabolic rates exceeds values previously reported for other teleost fish [50,51]. For example, in brown trout variation among individuals in SMR and maximum metabolic rate ranged from 12 to 14% [50].…”

“…For example, in brown trout variation among individuals in SMR and maximum metabolic rate ranged from 12 to 14% [50]. If this variation is heritable as suggested by other studies [51][52][53] and the individual variation in metabolic rates is associated with differential survival and other life-history traits [35,[54][55][56][57]; the greater variation among individuals may be important for evolutionary adaptation.…”

“…In two species of damsel flies, variation in thermal response affects both reproduction success and survival [22]. Similarly, metabolic rates have high heritability [51][52][53], and the individual variation in metabolic rates is associated with differential survival and other life-history traits [35,[54][55][56][57]. Finally, across taxa, there is a strong phylogenic signal for WAM and biogeographic distribution and habitat use [55,101].…”

mRNA expression explains metabolic and thermal physiology

“…There is significant literature investigating metabolic rate variation ( e.g. (31, 76, 77)); however, the relationship between metabolic rate and mRNA expression remains poorly understood. This may be due to the complex nature of whole animal metabolism, which is a sum of tissue specific metabolic demands and a balance between growth, maintenance, and energy storage.…”

“…To identify molecular mechanisms underlying physiological phenotypes, we quantified heart and brain mRNA expression among 86 F. heteroclitus individuals for which we had 6 measured physiological traits: whole animal metabolic rate (WAM), critical thermal maximum (CT max ), and four substrate specific cardiac metabolic rates (CaM substrates: glucose [Glu], fatty acids [FA], lactate+ketones+ethanol [LKA], and endogenous ) (26). These traits are heritable and related to fitness, and CaM traits have been previously explained by mRNA expression variation (6, 27–31). In these fish, trait-specific acclimation responses to 12°C and 28°C differed.…”