Experimental evidence for selection against fish larvae with high metabolic rates in a food limited environment

We provide experimental evidence for a direct link between embryonic metabolism and longevity in the larval stage of a marine fish when food resources are limited. Since growth rates of otoliths are closely related to metabolic rates, the area inside the hatch check (i.e., deposition of otolith matrix during embryonic development) is representative of inherent differences in metabolic rates. When exposed to food limitation, larvae with larger hatch check areas died earlier than larvae with smaller hatch check areas. This relationship did not occur in larvae that fed at saturated levels. A simple explanation for these observations is that larvae, which consumed metabolic fuel at higher rates died earlier unless energy derived from food was not limiting. Since high growth rates are linked to high metabolic rates, this mechanism could efficiently counteract selection for faster average growth but only when resources are limiting.