Ultrastructure and Morphology of Compound Eyes of the Scorpionfly Panorpa dubia (Insecta: Mecoptera: Panorpidae).

Qing-Xiao Chen,Bao-Zhen Hua,Eric James Warrant

doi:10.1371/journal.pone.0156970

Qing-Xiao Chen, Bao-Zhen Hua + Show 1 more

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https://doi.org/10.1371/journal.pone.0156970

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Abstract

Mecoptera are unique in holometabolous insects in that their larvae have compound eyes. In the present study the cellular organisation and morphology of the compound eyes of adult individuals of the scorpionfly Panorpa dubia in Mecoptera were investigated by light, scanning electron, and transmission electron microscopy. The results showed that the compound eyes of adult P. dubia are of the apposition type, each eye comprising more than 1200 ommatidia. The ommatidium consists of a cornea, a crystalline cone made up of four cone cells, eight photoreceptors, two primary pigment cells, and 18 secondary pigment cells. The adult ommatidium has a fused rhabdom with eight photoreceptors. Seven photoreceptors extend from the proximal end of the crystalline cone to the basal matrix, whereas the eighth photoreceptor is shorter, extending from the middle level of the photoreceptor cluster to the basal matrix. The fused rhabdom is composed of the rhabdomeres of different photoreceptors at different levels. The adult ommatidia have the same cellular components as the larval ommatidia, but the tiering scheme is different.

Highlights

Compound eyes are the prominent visual organs for the majority of insects [1]
Adults of P. dubia possess a pair of elliptical compound eyes and three oval dorsal ocelli on the heads (Fig 1A)
A data collection of single specimen measurements from the presented micrographies is listed in Table 1, where the ultrastructural measurements were made from the central regions of male compound eyes of P. dubia

Summary

Introduction

Compound eyes are the prominent visual organs for the majority of insects [1]. Unlike the single-chamber eyes of vertebrates, the compound eyes of insects are generally composed of many independent optical units called ommatidia [2] and can perform significant functions of flight control, navigation, prey capture, predator avoidance, and mate recognition [3,4,5,6]. The two basic optical designs of the insect compound eyes are the apposition type and the superposition type [4,12]. There is a pigmentless clear zone between the cornea and rhabdomeres [13], so that all photoreceptors share corneal dioptrical units, increasing the light sensitivity of the eye [14].

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