FEEDING AND OXYGEN UPTAKE OF THE TROPICAL SEA URCHIN EUCIDARIS TRIBULOIDES (LAMARCK)

1. In the laboratory Eucidaris tribuloides showed a food preference for rock infested with the boring sponge Cliona lampa over turtle grass (Thalassia testudinum), several algae, and fish strips. 2. In the laboratory, urchins consumed wet rock infested with Cliona lampa at rates ranging from less than one to over three gm. per day depending on the size of the urchin. 3. Oxygen consumption of urchins was measured in the laboratory with a modified Scholander volumetric respirometer. 4. Oxygen uptake decreased significantly during the first day of starvation, but then remained relatively stable during several successive days of starvation. 5. There was not a significant correlation between gonad index or sex of the urchin and relative oxygen uptake. 6. Relative oxygen consumption decreased with increasing size of the urchin. Values for "b" indicated an oxygen uptake which was almost proportional to surface area at 20° and 30 ° C. 7. Oxygen uptake fluctuated during the first hour when urchins were placed in water several degrees colder than their ambient water. At the end of this hour, however, the rate of oxygen uptake had become relatively stable. Well-fed urchins manifested greater changes in their stabilized rates of oxygen uptake (Q₁₀) at different temperatures than did starved urchins. 8. Urchins manifested partial seasonal acclimation of oxygen uptake as indicated by the fact that winter oxygen consumption curves were well above summer curves at the corresponding temperatures. The acclimation was probably not complete since mean summer oxygen uptake was higher at the summer ambient than the mean winter oxygen uptake at the winter ambient.