Non-invasive recording of electroretinogram from both compound eyes in the cockroach <i>Periplaneta americana L.<i> in response to light stimuli

Abstract

The paper presents an original method of non-invasive registration of electroretinogram from both compound eyes of an insect. The method demonstrated high reliability and repeatability of the results. Using this method, it was shown that the magnitude of the light responses obtained from mutant cockroaches devoid of screening pigment, pearl, was about 4 times greater than those of wild-type insects. The time to peak of the response decreased with increasing light intensity, both for short-wavelength and long-wavelength stimuli. The pearl cockroaches exhibited a faster time to peak response than wild-type cockroaches; the results of covariance analysis indicate that these differences cannot be fully explained by an increase in the number of photons reaching the photoreceptor membranes and suggest additional differences in the compound eye physiology of mutant and wild-type insects. The positive voltage wave after the end of light stimulation depends on light intensity and reflects hyperpolarization of receptor cells. The photovoltaic effect, which distorts the amplitude and the shape of the response can be eliminated by using a gold wire as a recording electrode.