General morphology of the brain of the blind cave beetle, Neaphaenops tellkampfii Erichson (Coleoptera : Carabidae)

Abstract

Neaphaenops tellkampfii (Coleoptera : Carabidae) was collected from Cartmill Cave located in Hart County, Kentucky, U.S.A. This is a cave insect with complete absence of external evidence of eyes or ocelli. The brain of N. tellkampfii has been studied at the light microscope level using Rowell's (1963) silver staining method. Particular attention has been paid to the protocerebrum. One of the notable features of the brain is the dominance of the corpora pedunculata. The corpora pedunculata consists of a calyx, with 3 groups of fibers originating from the Kenyon cells. The stalk is arranged into 2 distinct layers with alpha and beta lobes. The central complex is located anterio-medially beneath the pons cerebralis. It consists of central and ellipsoid bodies and a single ventral tubercle. The ellipsoid body is connected to the beta lobes by a unique chiasmatic fiber tract. The pons cerebralis appears to be formed by 3 distinct groups of globuli cells sending fibers into the pons. The accessory lobes are situated posterio-laterally. The antennal lobes are located posterio-ventrally. Two tubercles were observed lateral to the protocerebrum which may be vestigial optic tubercles. There is no evidence of typical optic lobes or associated fiber tracts. Fiber connections were observed between the calyx and pons cerebralis, the calyx and central body, and also between the calyx and antennal lobe. Two fiber tracts not previously described were observed extending obliquely from the accessory lobe to the beta lobe and protocerebrum.