LAUSR

Abstract Energy budget and resource distribution were evaluated for the sea urchin Paracentrotus lividus from the Eastern Mediterranean, reared in relatively low (20–22 °C) and high (24–26 °C) temperature regimes. Energy expenditure was quantified for the processes of respiration, excretion, growth and reproduction, as well as the amount and energetic content of the food consumed and its absorption rates. Unfed sea urchins were used to calculate basal energy requirements. A significant trade-off was found between the physiological parameters in response to the different water temperature regimes. In particular, a give-and-take between consumption and absorption rates was observed. Low consumption and high absorption took place in the cold-water treatment, while lower absorption rates in the warmer treatment were compensated for by higher consumption. Energy surplus was distributed through different channels. Investment in growth was significantly more prominent in colder water, whereas in the warm-water treatment investment in reproduction was higher. Total energy expenditure on activity significantly increased with higher water temperature, with a difference of ~40% between the coldest and warmest temperatures; however, expenditure above basal requirements was similar at both temperature levels. Our results show that P. lividus reared in the colder range of temperatures had a more efficient energy expenditure ratio, resulting in a higher (by ~10%) scope for growth than in warmer water. This study confirms the importance of water temperatures as the driver of natural ontogenetic processes in this species. Our data has great relevance for the farming of P. lividus.