Development of the compound eyes of dragonflies (odonata). I. Larval compound eyes

Abstract

AbstractInterommatidial angles and numbers of ommatidia that viewed each segment of the visual field were mapped for a variety of dragonfly larvae from four families, selected for different behaviors and phylogenetic divergence, by measuring the directions of view of ommatidia contributing to the pseudopupil.The size of the visual field and the amount of interommatidial angle specialization are greater than reported from histological sections, primarily because the optical axes are not perpendicular to the cornea.Each species has interommatidial angle specializations that match its behavior. Larvae which are visual predators (family Aeshnidae) have interommatidial angles which vary from 4.9° in some parts of the eye to as little as 0.13° in the developing ommatidia at the anterior border. A foveal area can be defined with interommatidial angles of 0.2° which is the theoretical limit for ommatidia of their diameter, and is narrower than the interommatidial angles reported for adult insects. Foveal interommatidial angles measured along a vertical plane are considerably smaller than along a horizontal plane, resulting in an extremely elongate pseudopupil.Larvae which are less dependent on vision for prey capture have correspondingly less structural specialization in the eye, but the same pattern of regional variation is still recognizable.In contrast to the great range of interommatidial angles, ommatidial diameters are relatively uniform; the inverse relationship expected for highest visual acuity is not found.