Investigations With a Saprozoic Nematode, Mesodiplogaster Lheritieri, On a Possible Respiratory Function of Air Swallowing

Experiments were done in which the oxygen and carbon dioxide tensions could be changed in a medium containing nematodes in order to examine the hypothesis that air swallowing in saprozoic nematodes might have a respiratory function. In these experiments, alternating high and low oxygen and low and high carbon dioxide tensions were produced in a liquid medium containing nematodes by perfusing the medium with pure oxygen gas on the one hand and with pure nitrogen gas or a gas mixture (80 % N2 + 15 % CO2 + 5 % O2) on the other. When applying oxygen and nitrogen alternately, a slight but significant increase in air swallowing occurred with nitrogen treatments compared with oxygen (table I). If the gas mixture was used instead of nitrogen thereby producing a low oxygen tension combined with an elevated CO2-tension, the increase in the frequency of air swallowing was much more pronounced (Table II). In control experiments in which nitrogen or the gas mixture were used continually, no regular changes in frequencies of air swallowing were observed (Table III). The results presented are interpreted as supporting the hypothesis that air swallowing has a respiratory role in Mesodiplogaster lheritieri.