Non-universal Interspecific Allometric Scaling of Metabolism

TL;DR

This paper develops a theoretical model for interspecific metabolic scaling, incorporating biological transport processes and extra dimensions, to explain variations in metabolic rates across species.

Contribution

It introduces a multi-dimensional framework including transport mechanisms to derive allometric exponents for metabolism, extending previous theories.

Findings

BMR exponent predicted as 0.71, close to empirical 0.69

Maximum MMR exponent predicted as 0.86, close to empirical 0.87

3/4-law identified as an upper limit for BMR

Abstract

We extend a previously theory for the interspecific allometric scaling developed in a $d+1$-dimensional space of metabolic states. The time, which is characteristic of all biological processes, is included as an extra dimension to $d$ biological lengths. The different metabolic rates, such as basal (BMR) and maximum (MMR), are described by supposing that the biological lengths and time are related by different transport processes of energy and mass. We consider that the metabolic rates of animals are controlled by three main transport processes: convection, diffusion and anomalous diffusion. Different transport mechanisms are related to different metabolic states, with its own values for allometric exponents. In $d=3$, we obtain that the exponent $b$ of BMR is $b=0.71$, and that the aerobic sustained MMR upper value of the exponent is $b=0.86$ (best empirical values for mammals: $b=0.69(2)$ and $b=0.87(3)$). The 3/4-law appears as an upper limit of BMR. The MMR scaling in different conditions, other exponents related to BMR and MMR, and the metabolism of unicellular organisms are also discussed.