Insect acid-base physiology

Acid-base status influences many aspects of insect biology, including insec t distributions in aquatic systems, insect-plant and insect-pathogen intera ctions, membrane transport phenomena, and the mode of action of pesticides. Acid-base status in the hemolymph and gut lumen of insects is generally we ll regulated but varies somewhat within individuals owing to effects of tem perature, activity, discontinuous ventilation, and diet. The pH of the midg ut lumen varies with the phylogeny and feeding ecology. Insect fluids have buffer values similar to those of vertebrates. The respiratory system parti cipates in acid-base homeostasis primarily by regulating the internal carbo n dioxide (partial) pressure via changes in spiracular opening and convecti ve ventilation. The epithelia of the renal system and gut participate in he molymph acid-base regulation by varying acid-base transport in response to organismal acid-base status. Evidence to date suggests that the dominant me chanisms for control of renal acid-base excretion involve hormonal regulati on of H+-V-ATPase activity.