A COMPARATIVE STUDY OF P³² UPTAKE BY WHOLE ANIMALS AND ISOLATED BODY REGIONS OF THE SEA CUCUMBER HOLOTHURIA ATRA

¹ Department of Zoology, Arizona State University, Tempe, Arizona 85281

1. When non-sterile H. atra is exposed to a sea-water medium containing P³², a decrease occurs in activity in the medium over time and is greatest during the first 12 hours of incubation. The isotope uptake is reflected by an increase in phosphorus activity in the tissue components.

2. Sterile holothurians show considerably less integumental P³² uptake than do non-sterile specimens, indicating active bacterial accumulation of the isotope, and to a lesser degree, uptake by H. atra.

3. The removal and concentration of P³² into the integument seems to be constant over the entire length of the animal, as well as being a function of the mass of the organ; the larger the integument, the smaller the uptake and concentration of the isotope per gram of tissue.

4. The greatest site of P³² uptake from solution appears to be by way of the general integumentary surface and through the anal-respiratory tree complex, while the oral region of the animal removes very little P³² from solution.

5. A high accumulation of P³² occurs in the respiratory trees under both sterile and non-sterile conditions, indicating a possible metabolic utilization of phosphorus by these organs. The major pathway of phosphorus entry to the coelomic cavity in H. atra is by passage across the respiratory trees.