Directly below the lens aperture, the photosensitive microvilli of neighboring retinular cells interdigitate, creating a rhabdom
that in cross section appears like the spokes of a wheel (Fig.
Though a regular arrangement of rhabdomeric microvilli was not found, we postulate that this area represents a simple closed rhabdom
An open rhabdom
structure in the ommatidia of Heteroptera is considered a synapomorphy for Heteroptera, in contrast to the fused rhabdoms
in Auchenorrhyncha and Coleorrhyncha (Fischer et al.
Of course, there are many additional questions that remain unanswered in spiders, ranging from the evolutionary basis of variation in field of view to the developmental control of rhabdom
size and shape.
The distal half of the sensory cavity is filled with a matrix of microvilli from the sensory cell, resembling a rhabdom
argus eyes contain two spectral classes, with visual pigment in the cells of the main rhabdom
(R1-7) absorbing maximally at 510 nm and pigment in the eighth retinular cells (R8) at 370 nm (Cummins et al.
The crystalline cone, which is the product of two cells, lies directly below the cornea and is attached to the tip of the rhabdom
of the retinula cells.
plebs, which has about 260 ommatidia with the five retinular cells per rhabdom
typical of other amphipods (Hallberg et al.
These limits exist because each photoreceptor unit of a compound eye, termed a rhabdom
, is paired with an individual optical system.
For most superposition compound eyes, the tapetum should, ideally, be formed of reflecting pigment enclosing the proximal third of each rhabdom
max] = 495 nm, when rhabdom
length and photopigment specific absorbance were considered.
The damage manifests itself as irreversible rhabdom
breakdown and changes to other structures in the eye (Gaten et al.