title: Effects of diet on titratable acid-base excretion in grasshoppers.
abstract: Despite the potential for diet to affect organismal acid-base status, especially in herbivores, little is known about the effects of diet on acid-base loading and excretion. We tested the effects of diet on acid-base loading and excretion in grasshoppers by (a) comparing the fecal acid-base content of 15 grasshopper species collected from the field and (b) comparing fecal acid-base excretion rates of Schistocerca americana grasshoppers fed vegetable diets that differed in their ashed and raw acid-base contents. The field experiments indicated that grass-feeding species excrete fairly neutral fecal pellets, while forb/mixed-feeding species vary widely in their fecal acid-base contents. In the laboratory experiment, acid-base excretion rates were positively correlated with dietary ashed base intake rates but were not correlated with the acid-base content of raw, unashed diet or feeding rate. These experiments suggest that some diets could strongly challenge the acid-base homeostasis of herbivores; in some grasshoppers, dietary acid-base loads could produce certainly lethal 1-unit changes in average body pH within 6 h if they were not excreted.
authors.affiliation: Department of Biology, Arizona State University, Tempe, Arizona 85287-1501, USA. fraz5@asu.edu.
authors.forename: M R
authors.initials: MR
authors.lastname: Frazier
authors.forename: J F
authors.initials: JF
authors.lastname: Harrison
authors.forename: S T
authors.initials: ST
authors.lastname: Behmer
mesh_terms: D000136:Acid-Base Equilibrium; D000222:Adaptation, Physiological; D000818:Animals; D004032:Diet; D005243:Feces / Q000737:chemistry; D006110:Grasshoppers / Q000502:physiology*; D006706:Homeostasis; D010944:Plants / Q000737:chemistry