Respiration in the burrowing brittlestar, Hemipholis elongata Say (Echinodermata, Ophiuroidea):: a study of the effects of environmental variables on oxygen uptake

The burrowing brittlestar Hemipholis elongata (Say) maintains a Constant M-O2 of 3.79 +/- 1.47 mu mol O-2 g(-1) h(-1) (for 0.2-0.3 g animals, mean +/- S.D., n = 7), measured in the burrow, over a broad range of PO,. Below the critical PO, of 37 mmHg, (M) over dot(O2) becomes dependent on the oxygen tension. (M) over dot(O2) is a function of the size of H. elongata; the scaling exponent is 0.83 and is similar to those reported for other echinoderms. The (M) over dot(O2) of H. elongata is unaffected by removal from the burrow, by hypercapnia, by exposure to hydrogen sulfide, or by temperature change in the range from 20 to 32 degreesC. The relative insensitivity of H. elongata to these factors may be an adaptation to life in the highly variable estuarine and tidal creek environments where the animals are frequently found. (C) 2000 Elsevier Science me. All rights reserved.