DOI: 10.5061/dryad.0gb5mkm0w
title: Interindividual plasticity in metabolic and thermal tolerance traits from populations subjected to recent anthropogenic heating

description: To better understand temperature’s role in the interaction between local
 evolutionary adaptation and physiological plasticity, we investigated
 acclimation effects on metabolic performance and thermal tolerance among
 natural Fundulus heteroclitus populations from different
 thermal environments. F.
 heteroclitus populations experience large daily and
 seasonal temperature variations, as well as local mean temperature
 differences across their large geographic cline. In this study, we focus
 on three populations: one locally heated (32°C) by thermal effluence (TE)
 from the Oyster Creek Nuclear Generating Station, NJ and two nearby
 reference populations that do not experience local heating (28°C). After
 acclimation to 12°C or 28°C, we quantified whole animal metabolic rate
 (WAM), critical thermal maximum (CTMax) and substrate specific cardiac
 metabolic rate (CaM, substrates: glucose, fatty acids, lactate plus
 ketones plus ethanol, and endogenous [i.e., no added substrates]) in ~160
 individuals from these three populations. Populations showed few
 significant differences due to large interindividual variation within each
 population and variation in acclimation response within any single trait.
 In general, for WAM and CTMax the interindividual variation in acclimation
 response (log2 ratio 28°C/12°C) was a function of performance at
 12°C with greater acclimation response for individuals that had lower 12°C
 performance. In contrast, for CaM the rates when acclimated and
 assayed at 12°C or 28°C were nearly identical. The small differences in
 CaM between 12°C and 28°C temperature were partially explained by cardiac
 remodeling where individuals acclimated to 12°C had larger hearts than
 individuals acclimated to 28°C, resulting in a higher CaM rate per unit
 heart mass at 28°C than 12°C. Correlation among physiological traits were
 dependent on acclimation temperature. For example, WAM was negatively
 correlated with CTMax at 12°C but positively correlated at 28°C.
 Additionally, glucose substrate supported higher cardiac metabolism than
 fatty acid, and fatty acid supported higher cardiac metabolism than LKA or
 endogenous. However, these responses were highly variable with some
 individuals using much more FA than glucose. These data suggest a complex
 relationship between specific, temperature-dependent physiological
 traits. 
description: Whole animal metabolism, substrate specific cardiac metabolic
 rate and critical thermal maximum were measured in individuals from three
 wild caught Fundulus heteroclitus populations. All traits were measured
 after individuals were common gardened at 20°C and 15ppt salinity for 6
 weeks then overwintered at 10°C and 15ppt salinity for 4 weeks.
 Individuals were then acclimated to 12°C or 28°C and 15ppt salinity for 4
 weeks and whole animal metabolism was measured followed by critical
 thermal maximum one week later. Individuals were then acclimated to the
 opposite temperature (12°C to 28°C or 28°C to 12°C) for 4 weeks before
 repeating trait measures in the following order: whole animal metabolism,
 critical thermal maximum, substrate specific cardiac metabolic rate. All
 traits were measured at the acclimation temperature. Whole animal
 metabolic rate was measured using intermittent flow respirometry. Critical
 thermal maximum was measured by placing fish in a 10 gallon aquarium with
 fully oxygenated 15ppt seawater at the acclimation temperature. Water was
 slowly heated (0.3°C per minute) using a submersible heating coil.
 Critical thermal maximum was defined as the temperature at which the
 individual exhibited no coordinated movement for 5 consequtive
 seconds. Cardiac metabolic rate was measured with four substrates:
 glucose, fatty acids, lactate with ketones and ethanol, and endogenous
 (i.e., no added substrate). To measure cardiac metabolic rate, heart
 ventricles were dissected, splayed in ringer's media with hepes, and
 placed in 1mL chambers with the desired substrate to measure oxygen
 consumption over time. Processed data (multiple replicate measures of
 oxygen consumption over time averaged for a single individual) for whole
 animal metabolic rate and substrate specific cardiac metabolic rate are
 provided here. Raw critical thermal maximum data in °C are also provided.
 Metadata includes population, acclimation temperature, acclimation order
 (12°C first or 28°C first acclimation), habitat temperature, body mass (at
 time of whole animal and cardiac metabolic rate), heart mass, date of data
 collection, and sex for all individuals. Mass corrected metabolic rates
 (log10 regression with body mass for whole animal and regression with body
 mass for cardiac metabolic rate) are also included in the data
 set.
description: Please reference the "Notes" tab of the data file for
 descriptions of abbreviations used, units for trait measures, and
 important information about metadata columns and missing data.