Phylogenetic and Functional Implications of the Rhabdom Patterns in the Eyes of Chrysomeloidea (Coleoptera)

Ultrastructural data from 108 species of Chrysomeloidea show that all rhabdom-patterns can be assigned to one of two basic patterns. The insula-pattern: two central rhabdomeres (Rh 7/8) are spatially isolated from the six peripheral ones (Rh 1–6). The ponticulus-pattern: Rh 7/8 fuse at two sites with the ring of Rh 1–6. The distance between the two systems may prevent optical or electrical coupling in the insula-p. The structure of the ponticulus-p may allow electrical coupling as well as contrast-intensifying lateral filtering. Potential relative polarization and absolute sensitivities differ interspecifically between homologous cells and intraspecifically between Rh7/8 and Rh 1–6, and between Rh 7 and Rh 8. The Bruchidae show only the insula-p, the Chrysomelidae and Cerambycidae both. The distribution of the two patterns is subfamily-specific within the Chrysomelidae, but not in the Cerambycidae. Identical patterns must have developed convergently within the Chrysomeloidea. Both basic patterns are subdivided in different subfamilies or tribes.