External morphology and ultrastructure of the compound eyes of Ricania speculum (Hemiptera: Fulgoroidea: Ricaniidae)

Abstract

The external morphology and ultrastructure of the compound eyes of the adult Ricania speculum (Walker, 1851) are studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The adult compound eyes of R. speculum are of the apposition type. Each ommatidium contains a laminated corneal lens, a crystalline cone, eight retinula cells, two primary pigment cells, six secondary pigment cells and a basal lamina. Eight retinula cells (R1–R8) provide microvilli to form a central rod-like rhabdom, but only six distal retinula cells (R1–R6) appear at the distal end of the rhabdom where the retinula cells R7 and R8 are inserted between R1 and R6. Fulgoromorphan species studied so far have eight retinula cells that provide microvilli to form a rod-like rhabdom, and the presence of seven distal retinula cells and eight retinula cells in the proximal end probably represents the ground-plan of Fulgoromorpha. More comparative studies are needed to document the extent of variation in ultrastructure of the compound eyes of Fulgoromorpha and to identify characters of potential use for phylogenetic analysis of Auchenorrhyncha and further elucidate the evolution of visual systems in this group.