# The thermodynamic opportunities hypothesis: Metabolic temperature insensitivity across flatfish species

## TL;DR

Flatfish metabolic rates do not change with temperature, suggesting evolution and ecology, not thermodynamics, explain this trait.

## Contribution

Proposes an evolutionary and ecological explanation for temperature-insensitive metabolism in flatfish.

## Key findings

- Metabolic rates in flatfish remain constant across different temperatures.
- Camouflage reduces predation pressure, eliminating the need for higher metabolic rates in warm waters.

## Abstract

This study challenges widely held metabolic theory, which suggests that whole-animal metabolic rates increase with temperature because of its universal effects on the kinetics of the underlying biochemical reactions. Here, we show that metabolic rates across flatfish species are largely invariant from poles to the equator, which points to an explanation for interspecific thermal sensitivity based on ecology and evolution rather than thermodynamic constraints. The explanation proposed here is that warm water provides a thermodynamic opportunity, not a mandate, for metabolic rate escalation when required for predator-prey interactions. Flatfish do not require metabolic escalation because of their reliance on camouflage that mitigates the greater predation intensity in tropical waters. These findings have strong implications for models attempting to diagnose the response of organisms to climate change and for macroecological patterns more generally.

Flatfish metabolism is temperature-insensitive, suggesting an evolutionary explanation rather than a thermodynamic constraint.