Electrophysiological measurements of spectral sensitivity of central visual cells in eye of blowfly

Abstract

IN 1913 von Frisch was able to show that bees can discriminate between different colours. He thus refuted the then prevailing opinion that only certain vertebrates have colour vision. Since then insect colour vision has become a significant subject of research, the more so in view of the fact that using insect visual cells the transformation of light into neural excitation can be readily examined. In recent years numerous electrophysiological, microspectrometric and behavioural experiments have been carried out to determine the spectral sensitivity of visual cells not only of the bee but also of the fly. In the case of the blowfly Calliphora erythrocephala, each compound eye is made up of approximately 3,000 ommatidia. Under the lens of each ommatidium there are eight visual cells, and these can be divided into two groups according to their shape. Six of them (numbered R_1–6) have short axons which end in the first optic ganglion (lamina ganglionaris). The remaining two visual cells (R₇₊₈, also called ‘central visual cells’ because of the position they occupy in the ommatidium) are characterised by their long axons, which stretch from the retina through the lamina ganglionaris down to the second optic ganglion (medulla).