The Control of Respiratory Movements in Crustacea by Oxygen and Carbon Dioxide

THE effects of an accumulation of carbon dioxide and of a lack of oxygen on the respiratory movements of mammals have been intensively studied (Winterstein, 1923; Gesell, 1925). In the invertebrates, however, although it is known for a number of species that one or both of these two factors are operative, our knowledge of the whole question is fragmentary. Both an accumulation of carbon dioxide in the environment and a deficiency in oxygen accelerate the ventilation movements of the stick insect Dixippus (Buddenbrock and Rohr, 1922; Stahn, 1928) and those of the "Maikafer" (Demoll, 1928). In the cockroach Periplaneta and other insects the stigmata, which are normally almost closed when the animal is at rest, open in response to small quantities of carbon dioxide; but only a great reduction in oxygen produces this effect on the cockroach's stigmata (Hazelhoff, 1927). Both carbon dioxide excess and oxygen lack accelerate the limb movements of the phyllopod crustacean Branckipus, which serve for respiration as well as for swimming and feeding (Babak, 1921). In the pulmonate molluscs Arton, Limax and Helix, an increase in carbon dioxide results in an enlargement of the respiratory aperture, while oxygen lack causes contractions of the lung wall (Dahr, 1924; Ysseling, 1930). In Octopus both a rise in carbon dioxide and a fall in oxygen tension increase the respiratory volume up to ten times its normal value, usually with little alteration in the frequency of the respiratory movements (Winterstein, 1925). A rise in the tension of carbon dioxide in the sea water accelerates the respiratory rhythm of the abdominal appendages in the stomatopod crustacean SquUla, but a