The influence of temperature and oxygen on the photomechanical system of the mealmoth eye

Abstract

1. Optical and electrophysiological measurements on the eyes of living moths,Ephestia kuehniella, show that aggregation of secondary pigment cell granules occurs only in the temperature range 5 to 37°C. At temperatures outside this range the granules are always dispersed, even when the moths are in the dark. The state of aggregation is maximal at about 20°C, as measured by reflectance. The temperature-dependent decrease in reflectance induced by test illuminations (identical in wavelength, intensity and flash duration), as an indication of the translocation of the granules towards the dispersed state, is strongest at about 25°C. 2. Electroretinograms (ERGs) were recorded in the range from −5 to 42°C. The temperature dependence of ERGs gives an asymmetrical curve with a maximum between 10 and 15°C. The difference in the position of this maximum compared to those of reflectance values is discussed, together with results from a white-eyed mutant. 3. Oxygen consumption of moth heads is independent of light or dark adaptation in both wildtype and mutant moths. TheQ10 values of oxygen consumption are between 2 and 3. Inhibition of the aggregation of screening pigment granules by colchicine does not change O2 consumption. When mixtures of oxygen and nitrogen (O2/N2) are applied to mealmoths, aggregation of granules does not occur with less than 3% O2. At O2 levels between 10% and 100%, granule migration is constant. At O2 levels between 3 and 10%, change in reflectance after a given light stimulus increases with decreasing O2 concentration.