Photoreceptor Structures. the Retinal Cells of the Cockroach Eye

The retinal structures of the compound eyes of insects are being investigated as par t of a comparative study of the s tructure and biochemistry of visual organs (1 5). T he compound eye of the insect is composed of numerous ommatidia , each of which consists of f rom four to eight re t inula cells. Each re t inula cell contains a differentiated structure, the rhabdomere , a photoreceptor . The rhabdomeres are analogous in function to the retinal rods of the ver tebra te eyes. One of the more primit ive of the unspecialized insects is the cockroach. I t has been suggested from electrophysiological studies tha t the cock) roach eyes contain two types of visual photoreceptor systems (6, 7). I t was, therefore, of interest to us to determine the fine structure of their rhabdomeres and to isolate their photosensitive pigments in order to make a comparison with the photoreceptors of other insects and inver tebrate compound eyes. Two common, large species of cockroaches, Periplaneta americana and Blaberus giganteus, made available to us from the Gulf Research Laboratory , were used in this study. 1