The eye of Incisitermes minor: structure, functionality, and development

The adults of I. minor have compound eyes that are similar to those of cockroaches, comprised of up to 300 ommatidia. Under each lens, there are four cone cells surrounded by pigment cells and the retinula cells form a closed rhabdom. While newly hatched individuals have no visible eye structures, the first molt produces some brown pigmented cells and the cuticle shows 8 to 12 “proto-lenses,” or small protrusions in the eye region that do not fill the available area. The number of proto-lenses as well as the number of pigmented cells increases with each successive molt. Since pigment in the eye is typically an indicator of functionality, and workers live constantly in darkness, we decided to test the functionality with electrophysiological experiments. The electroretinograms recorded from termite eyes look similar to those from many other insects, where within one second of stimulation, the ERG has an initial phasic peak followed by a tonic response maintained until the end of stimulation. Responses to light flashes of different durations, various intensities, and to different colors (red, blue, and green) also resemble that of other insects. Therefore, the eyes of the workers are fully functional without being fully morphologically developed.