Effects of CO 2 and anoxia on feeding, growth, metabolism, water balance, and blood composition in larval female house crickets, Acheta domesticus

Abstract

A single 5 min exposure of larval house crickets to CO 2 or N 2 caused a 12 hr feeding inhibition and a 24 hr drinking inhibition. Daily 1–5 min gas exposure throughout the last instar caused a minimal 1 3 reduction in total food consumption and 1 3 reduction in weight gain. The crickets were most sensitive to feeding-growth retardation in the first half of the instar, when almost all feeding normally occurs. Gas treatment also lowered the efficiency of food conversion to body weight. The mortality threshold, measured by survival to the final ecdysis, for daily exposures was about 5 min, but for a single exposure the threshold was about 30 min. The metabolic rate was very slightly depressed by 5 min of anoxia, but was depressed for over 2 days following 15 min of anoxia. Single 1–5 min gas treatments of 3 and 5 day old larvae led to an average 20 mg diuretic water loss over the following 2–3 hr. Blood pH was lowered by CO 2 (carbonic acid) and by N 2 (lactic acid). A brief 1–5 min of anoxia caused a blood lipid increase within 3 hr with recovery to normal in 24 hr; blood NPS decreased within 3 hr and returned to normal in 24 hr; blood sugars increased within 3 hr, then decreased below controls before returing to normal in 24 hr. Blood lactate concentration indicated the extent of anoxia caused by CO 2 and N 2 exposure. Nitrogen caused asphyxiation with almost immediate anoxia. Carbon dioxide caused an immediate anesthesia which stopped breathing. Thus CO 2 delayed the onset of anoxia but did not prevent it. Anesthesia resulted from the direct diffusion of CO 2 from tracheae into neurones, and did not via the blood. Neither lowered blood pH or high lactate concentration directly caused immobilization, feeding-growth retardation, or any alteration in blood organic composition. We suggest that as little as 1–5 min of anoxia caused a long term disruption of certain neuroendocrine functions, which resulted in 3 hr of diuresis, 12 hr of feeding inhibition, and 12–24 hr of deviations in blood sugars, NPS, and lipids.