The compound eye of the dung beetle, Onthophagus posticus (Coleoptera: Scarabaeidae)

Abstract

The structural organization of the eye of the dung beetle Onthophagus posticus was investigated by light and electron microscopy and compared with that of other scarabaeid beetles in an effort to relate eye anatomy and life style. The eye of O. posticus displays features like well-developed crystalline cones, presence of a clearzone, and fused rhabdoms of 7 rhabdomeres, which are in line with the phylogenetic and taxonomic position of this species. However, a slight departure from a strictly nocturnal mode of life is indicated by the high degree of orthogonally-arranged rhabdom microvilli of approximately 50 nm in diameter and the absence of a tracheal tapetum. It is concluded that the basis for e-vector detection is present in O. posticus, and, therefore, astro-orientation to maintain a straight path is possible. The division of the eye into a narrow dorsal sliver and a major ventral part is noted, but its functional reason remains enigmatic.

Keywords>:

• Insect compound eye
• sensory ecology
• electron microscopy
• scarab beetles (dung beetles