Linking the metabolic rate of individuals to species ecology and life history in key Arctic copepods

This study compares the active and resting metabolic rates of species and life stages of copepods during the Arctic winter. Measurements were taken on individuals, and rates were described as functions of body mass. Differences in metabolic rate between species and life stages with the same mass were taken as evidence of distinct lifestyles. Copepod species that opportunistically feed during winter had higher active metabolic rates than species in a dormant state, but their resting metabolic rates were similar. Furthermore, metabolic rate increased more rapidly with mass for males compared to females and juvenile copepods with the result that the largest males had much greater rates. Whether the copepod was active or at rest had the greatest effect on metabolic rate, followed by body mass, species, and life stage having the least effect. Individual measurements on copepods can facilitate comparisons of metabolic rate across mass and further enable the measurement of rates when the individuals are active or at rest. The plasticity in metabolic rate found in the present study enables winter active species to have as low metabolic rates as dormant species and then suddenly mobilize and increase metabolism, likely as an adaptation to the scarce and random food availability during winter.