Interactive effects of temperature and nutritional condition on the energy budgets of the sea urchins Arbacia punctulata and Lytechinus variegatus (Echinodermata: Echinoidea)

Arbacia punctulata and Lytechinus variegatus are widely distributed echinoid species in shallow water in the western Atlantic Ocean, Caribbean Sea and Gulf of Mexico that seem to have different life history strategies. We evaluated the effect of two types of stress (high temperature and starvation) on gonad production and scope for growth. We hypothesized that A. punctulata has a stress tolerant life strategy and would be more tolerant to stress and L. variegatus has a competitive-ruderal strategy and would be less tolerant to stress. Gonad production by A. punctulata was not as greatly affected by temperature as L. variegatus, suggesting the hypothesis was correct. Arbacia punctulata had a significantly higher excretion rate indicating greater energy allocation to maintenance than production. Lytechinus variegatus had a significantly greater consumption rate but did not absorb significantly more energy. Arbacia punctulata compensated for its lower food consumption by a higher absorption efficiency. Measured energy expenditure and calculated scope for growth did not differ. However, the percentage change in energy absorbed and energy expenditure was greater for L. variegatus than for A. punctulata with a change in temperature. Feeding had a greater effect on production than temperature suggesting that the biotic stress of low food availability is more important than an abiotic stress such as temperature on energy budgets.