Thermal physiology of the common eelpout (Zoarces viviparus)

Abstract

We investigated the temperature dependence of some physiological parameters of common eelpout (Zoarces viviparus) from different locations (North Sea, Baltic Sea and Norwegian Sea) on acclimation temperature (3°C and 12°C) and acute temperature variation. The lethal limit of 12°C-acclimated eelpout was determined as the critical thermal maximum [loss of equilibrium (LE) and onset of muscular spasms (OS)] and it was found to be 26.6°C for LE and 28.8°C for OS for all populations. However, these parameters do not have any relevant ecological interpretation. We therefore investigated the effect of gradually increased water temperature on standard metabolic rate (measured as resting oxygen consumption Mo 2 ) and critical oxygen concentration ([O 2 ] c ) of eelpouts. Acclimation to low temperature (3°C) resulted in partial compensation of Mo 2 , paralleled by a decrease of activation energy for Mo 2 (from 82 kJ mol -1 at 12°C to about 50 kJ mol -1 at 3°C) in North Sea and Baltic Sea eelpouts. At the same time, Norwegian eelpout showed no acclimation of oxygen demand to warm temperature (12°C) at all. The scope for eelpout aerobic metabolism shrank considerably with increased acclimation temperature, as [O 2 ] c approached water oxygen concentrations. At 22.5±1°C the [O 2 ] c reached air saturation, which is equivalent to the upper critical temperature (Tc II ) and at this temperature the aerobic scope for the metabolism completely disappeared. In line with previous insight, the comparative analysis of the temperature dependence of Mo 2 of Z. viviparus from different populations suggests that a pejus (sub-critical) temperature for this species is about 13-15°C. In conclusion, the capacity to adjust aerobic metabolism relates to thermal tolerance and the bio-geographical distribution of the species. Global warming would thus be likely to cause a shift in the distribution of this species to the North.Keywords Critical oxygen concentration AE Critical temperature AE Aerobic scope AE Pejus temperature AE Geographical distribution Abbreviations CTMax critical thermal maximum AE Fiv factor of inside volume AE G T total oxygen conductance AE LE loss of equilibrium AE LT 50 time period of exposure when mortality reaches 50% AE M O2 rate of oxygen consumption AE M O2 o rate of oxygen consumption at 0°C AE [O 2 ] c critical oxygen concentration AE OS onset of muscular spasms AE Tc critical temperature AE Tc ll upper critical temperature AE Tp pejus temperature

Cod and climate in a latitudinal cline: physiological analyses of climate effects in marine fishes

“…Specifically, heat limitation in eelpout (temperate Zoarces viviparus, Antarctic Pachycara brachycephalum) and Atlantic cod Gadus morhua begins with a limitation in oxygen supply capacity (Zakhartsev et al 2003, Lannig et al 2004Figs. 2 & 3), which leads to anaerobic metabolism, as indicated by the depletion of high energy phosphates and the onset of mitochondrial succinate formation and accumulation (e.g.…”

Oxygen limited thermal tolerance in fish?

“…Metabolites in spectrum (A) originated from embryonic fish, whereas almost no signal (except for residual water) arose in spectrum (B) where no embryo was present (after Bock et al, 2002a). peratures. Progressive warming resulted in increased arterial and venous blood flow until it remained unchanged despite a continued rise in oxygen demand Zakhartsev et al, 2003). Above a critical temperature invasive work reported succinate accumulation in liver .…”

“…In consequence, Zakhartsev et al (2003) studied the temperature dependence of the critical oxygen tension (P c ) in eelpout, Z. viviparus. The P c was determined as the oxygen tension below which the rate of oxygen consumption fell below the regulated value when the animal was exposed to progressive hypoxia.…”

“…Critical temperatures as discussed here border the temperature range that permits performance on top of baseline energy expenditure and are likely reached before the onset of spasms (Zakhartsev et al, 2003) which are traditionally used to define critical thermal maxima (Lutterschmidt and Hutchison, 1997a,b). Within the thermal tolerance window aerobic performance increases with temperature to a maximum and then decreases at higher temperatures yielding a species-specific asymmetric bell shaped curve, which shifts depending on thermal adaptation (Angilletta et al, 2002).…”

Untitled

“…The capacity of thermal compensation has been considered to be related with fitness and biogeographic range of ectothermal species under climate change (Chevin, Lande, & Mace, 2010;Somero, 2010;Schulte, Healy, & Fangue, 2011;Sandblom et al 2014). Even though, metabolic compensation may not be a general mechanism across species (Clarke & Johnston, 1999;Zakhartsev, De Wachter, Sartoris, Pörtner, & Blust, 2003;Clarke, 2006).…”