THE EFFECT OF SIZE, TEMPERATURE, OXYGEN LEVEL AND NUTRITIONAL CONDITION ON OXYGEN UPTAKE IN THE SAND DOLLAR, MELLITA QUINQUIESPERFORATA (LESKE)

¹ Department of Biology, University of South Florida, Tampa, Florida 33620

1. Rates of respiration in a closed vessel conformed to oxygen concentrations in surrounding water until a low level (1 ml O₂/liter) of oxygen was attained.

2. Respiratory rates of small animals were proportionally higher on both a dry weight and nitrogen weight basis than rates of large animals (slope for ml O₂ respired/hr per animal was 0.5485 for dry weight and 0.5670 for nitrogen) in a closed vessel.

3. Respiratory rates of field acclimatized animals were slightly higher at summer temperatures (30-33° C) than at winter water temperatures (15-20° C) with evidence for partial acclimatization presented.

4. Respiratory rates of starved animals were lower than rates of non-starved animals with starvation depressing the rates of smaller animals more than rates of larger animals.

5. Respiratory rates in an open system were approximately twice as high as rates in a closed system due to greater activity of animals in the open system.

6. Comparison of day versus night respiration showed no obvious trends.

7. Respiratory rates of M. quinquiesperforata are slightly higher than rates of a similar weight, tropical, regular urchin as reported in the literature.