The regulation of respiration in the flea, xenopsylla cheopis , Roths. (Pulicidea)

Abstract

There are no ventilating movements in the flea; respiration is regulated only by the opening and closing of the spiracles. The closing mechanisms are described. In the flea at rest, the 3d thoracic (or, perhaps, 1st abdominal) and 8th abdominal spiracles show a rhythmical opening and closing; the other spiracles remain closed save during muscular exertion and at the height of digestion, when they too may show rhythmical movements or remain permanently open. The spiracles are caused to open chiefly by O2 want (CO2 contributing to a small extent) ; but the duration of the open period is determined mainly by the time taken for CO2 to diffuse away. The resp. centers of the abdominal spiracles are probably located in the corresponding ganglia; but some response to abnormal gas mixtures remains even after removal of the central nervous system. At low O2 pressures metabolites accumulate, raise the osmotic pressure of the blood, and increase the respiratory surface by extracting water from the ends of the tracheoles.