The physiology of the cricket's compound eye with particular reference to the anatomically specialized dorsal rim area

Abstract

1. The spectral, angular and polarization sensitivities of photoreceptors in the cricket's compound eye are measured by intracellular electrophysiology. The physiological characteristics of receptors in the anatomically specialized dorsal rim area (DRA) are compared with those of receptors in the adjacent dorsal area (DA) of the eye. 2. The study of (1) the direction of the optical axis of each cell tested (with respect to natural head position; Fig. 2), (2) the retinal position of intracellularly stained cells and (3) the shapes of the visual fields (see below) suggests that the DRA contains blue-receptors only(λmax=435 nm), where-as the DA is composed of green-(λmax=510 nm) and UV-receptors (λmax ca. 340 nm) (Fig. 1). 3. The visual fields of DA units exhibit the usual, narrow shapes with an average acceptance angle (Δρp) of 6°. In contrast, the visual fields of DRA receptors are much wider due to absence of screening pigment and corneal facets in this eye region: Δρ varies between 10° and 35°, but in many cells the angular sensitivity function is too broad to allow determination of Δρ (Figs. 3, 4). 4. Polarization sensitivity (PS) in blue-cells (DRA) is much higher (\(\overline {{\text{PS}}} = 8.3\)) than in green-cells (\(\overline {{\text{PS}}} = 2.6\)), although there is no retinular twist in both eye regions. PS values of two UV-cells examined were 2.9 and 4.2 (Fig. 5). 5. The possible role of the cricket's DRA for polarization vision is discussed by comparing the physiological characteristics of the cricket's DRA with those of the honey bee's DRA and in the light of recent behavioral experiments.