Influence of body mass and environmental oxygen tension on the oxygen consumption rates of an enteropneust, Glossobalanus crozieri

Abstract

The present study deals with a species of enteropneust, Glossobalanus crozieri, focusing on two aspects of its respiration: a) oxygen consumption and body mass, and b) the influence of environmental oxygen tension on the respiratory rate. Preliminarily, the body water content was shown to be 85% of the whole body weight. The regression coefficient of the oxygen consumption on the wet body mass (0.578) seems to agree with the view that in enteropneusts respiration is mainly cutaneous. The respiratory rate was significantly reduced at O 2 tensions from 76 mmHg downwards, suggesting conformity rather than regulation. Key wordsTongue or acorn worms are hemichordates of the class Enteropneusta, in which a short anterior structure is identified as notochorda. They are marine animals inhabiting mostly shallow waters and digging galleries in the sandy or muddy substrate. Different aspects of their biology have been studied (1,2), as well as their body chemical constituents (3-5), but their physiology has received much less attention, because of "their sluggish responses and tendency to break into pieces on handling" (2). Two of the existing papers refer to respiration. The ecology and respiration of Ptychodera flava from India were studied at both high and low tides (6). The respiratory rate (weight-specific oxygen consumption) determined at 25. The results also indicated a respiratory rhythm associated with the tidal cycle. In an accurate study of 31 invertebrates from 10 phyla, the oxygen consumption of Sacchoglossus kowalevski in the presence of declining oxygen (expressed as the term B 2 , when the data were analyzed to fit the quadratic equation) showed regulation rather than conformity (7). We now describe a species found in Brazil, Glossobalanus crozieri van der Horst 1924, focusing on the influence of body