ORGANIZATION OF THE LAMINA GANGLIONARIS OF THE OPTIC LOBE OF THE BUTTERFLY PARARGE AEGERIA (LINNE) (LEPIDOPTERA, SATYRIDAE)

The present work reports on a neuroanatomical study of the butterfly P ararge aegeria (Lepidoptera: Satyridae) focusing on the lamina ganglio naris underlying two different regions of the retina of the compound e ye: the dorsal rim area and the large dorsal region. No differences be tween both lamina regions, concerning the structure of the cartridges and the morphology of the identified neurons, could be detected. After passing the basement membrane, the visual cell axons are organized in retinotopic bundles (pseudocartridges), in which the axons of the 9 v isual cells (V1 and 5, D2, 4, 6, 8, H3 and 7, B9) are arranged in the same way as in the retina. In the pseudocartridge there are no synapti c contacts. Before entering the lamina cartridge, the bundles rotate 9 0 degrees. The cartridges are joined by the fibres of 4 monopolar cell s (L1, L2, L3 and L4), which could be identified and located inside th e lamina Cartridges in serial EM-sections. Golgi impregnations reveale d the morphology of these fibres. Thus, the regional specialization of the retina (dorsal rim area and large dorsal region) does not Seem to be reflected at the level of the first visual neuropil. Additionally, the cartridges of both lamina regions were investigated qualitatively for synaptic contacts among fibres. In addition to monadic chemical s ynapses and multiple contact synapses with presynaptic ribbons, cell c ontacts are also facilitated by invaginations and bridges. These cellu lar interactions and their functional implications are discussed. (C) 1997 Elsevier Science Ltd.