The visual system of the European corn borer (Ostrinia nubilalis) was analysed with microscopy and electrophysiological methods (electroretinograms and single-cell recordings). Ostrinia nubilalis has a pair of mainly ultraviolet-sensitive ocelli and a pair of compound eyes, maximally sensitive to green light. The ommatidia contain a tiered, fused rhabdom, consisting of the rhabdomeres of 9-12 photoreceptor cells with sensitivity peak wavelengths at 356, 413, 480 and 530 nm. The photoreceptors in a large dorsal rim area have straight rhabdomeres and high polarisation sensitivity (PS1,2=3.4, 14). Elsewhere, in the main retina, the majority of photoreceptors have non-aligned microvilli and negligible PS, but each ommatidium contains one or two blue-sensitive distal photoreceptors with straight microvilli parallel to the dorsoventral axis, yielding extremely high PS (PS1,2,3=56, 63, 316). Rhabdoms containing distal cells with potentially high PS have evolved at least twice: in moths (Crambidae, Noctuidae, Saturniidae), as well as in dung beetles (Scarabaeidae). The distal photoreceptors with high PS, sensitive to vertically polarised light, represent a monopolatic system, which is unsuitable for the proper analysis of electric field vector (e-vector) orientation. However, the distal photoreceptors might be used in conjunction with polarisation-insensitive photoreceptors to detect objects that reflect polarised light with stereotyped orientation.
Keywords: Compound eye; Intracellular recording; Moth retina; Photoreceptors; Polarisation sensitivity; Spectral sensitivity.
© 2017. Published by The Company of Biologists Ltd.