Nutrient deficiencies and the restriction of compensatory mechanisms in copepods

1.The flexible regulation of feeding behaviour and nutrient metabolism is a prerequisite for consumers to grow and survive under variable food conditions. Thus, it is essential to understand the ecological trade-offs that restrict regulatory mechanisms in consumers to evaluate the consequences of nutrient limitations for trophic interactions.

2.Here, we assessed behavioural and physiological adjustments to nutrient deficiencies in copepods and examined whether energy limitation, food digestibility or co-limitation with a second nutrient restricted compensatory mechanisms.

3.A combination of 13C-labelling and compound-specific stable isotope measurements revealed that copepods compensated nitrogen deficiencies by raising retention efficiencies of amino acids. The costs of higher retention efficiencies were reflected in the doubling of structural fatty acids, probably required for morphological adaptations of the gut. A depletion of highly unsaturated fatty acids in storage lipids a...