The control of respiratory movements in Crustacea by oxygen and carbon dioxide

THE investigations made by Fox and Johnson (1934) into the respiratory control of certain Crustacea showed that there was considerable variation in the response to carbon dioxide and oxygen. Thus the rate of limb movements of Balanus and Chirocephalus was not affected by the gas content of the water, whereas the respira-tory rhythm of Astacus and Asellus was quickened by oxygen lack, and that of Gammarus by both oxygen lack and carbon dioxide excess. Even within one genus some degree of variation was found, for whereas the effect of changes of the gas content of the medium on the rate of pleopod beat in G. pulex was permanent, in G. locusta it was transitory. It was hoped that by extending these investigations to more species of Crustacea, some phylogenetic or ecological significance might be discovered in this variation of response to the respiratory gases. I. SQUILLA MANTIS L. The respiratory organs of Sqwlla are described fully by Giesbrecht (1910). In the adult the exopodites of the pleopods bear large tufts of branchial filaments which are not developed in the young forms. The movements of the pleopods dra