GIBBS, V.K.*; WATTS, S.A.; Univ. of Alabama at Birmingham: The Effect of Temperature on Nutrient Absorption in the Regular Sea Urchin Lytechinus variegatus

Although seldom reported, temperature may be a key environmental factor influencing nutrient utilization in ectothermal organisms. The following study investigated nutrient absorption in response to three various exposure temperatures. Adult Lytechinus variegatus (ca 40mm diameter) were collected (n=88) in October 2001 from Saint Joseph Bay, Florida, and returned to UAB. The sea urchins were divided into nine 80-L aquaria (n=8 sea urchins per aquarium) maintained in enclosed incubators (n=3 aquaria per incubator) at a specific constant temperature of 16, 22, or 28&degC and 32 ppt salinity artificial seawater. Within each aquarium, individuals were maintained in 1-L containers with recirculation and were fed a prepared diet ad libitum daily for 8 weeks. Ingestion and egestion were recorded daily. At the end of week 8, final measurements of each individual were recorded. Total dry matter absorption efficiencies and absorption efficiencies of protein, carbohydrate, and lipid were calculated. The amount of each nutrient absorbed per individual was determined. Dry matter absorption efficiencies were highest for sea urchins held at 28&degC. Protein was more efficiently absorbed than lipid or carbohydrate. At week 8, individuals held at 16&degC had significantly higher protein absorption efficiencies than those held at 22 or 28&degC. Carbohydrate absorption efficiencies were highest at 28&degC and lowest at 16&degC. The amount of carbohydrate absorbed did not vary significantly among temperatures at week 8. Lipid absorption efficiency was highest for individuals held at 16&degC at week 8. These data suggest nutrient requirements/utilization changes with temperature.