Eye ultrastructure investigation of Scaphidium japonum Reitter (Coleoptera: Staphylinidae: Scaphidiidae).
The compound eye of the fungus beetle Scaphidium japonum Reitter was investigated using both light and electron microscopy techniques. The external appearance of the eye is found to be oval in shape and compromising 1400-1500 ommatidia. Each ommatida has dioptric apparatus and a layer of retinula cells. Dioptric apparatus include the cornea, corneal processes, and a crystalline cone. The retinula cells form the photoreceptor organ which is known as the rhabdom. The rhabdom is long, and wide at the distal region, which then becomes narrow at the most proximal region. Banded arrangement is observed in the rhabdom. The microvilli are parallel to each other in a rhabdomere. Seven retinular cells reach upto the cone level to form the fused rhabdom. The eighth retinular cell joins to the rhabdom at the proximal region of the ommatidia. Only one retinula cell nucleus appears at the most proximal regions of the ommatidia while the rest appear at the distal one third of the ommatidia. The eye ultrastructure of the Scaphidiidae depicts the adaptation towards a fungus habitat.