COMMON GENERAL MORPHOLOGICAL PATTERN OF PEPTIDERGIC NEURONS IN THE ARACHNID BRAIN - CRUSTACEAN CARDIOACTIVE PEPTIDE-IMMUNOREACTIVE NEURONS IN THE PROTOCEREBRUM OF 7 ARACHNID SPECIES

A polyclonal antiserum raised against crustacean cardioactive peptide labels 14 clusters of immuno-reactive neurons in the protocerebrum of the spiders Tegenaria atrica and Nephila clavipes, and the harvestman (opilionid) Rilaena triangularis. In all species, these clusters posse ss the same number of neurons, and share similar structural and topolo gical characteristics. Two sets of bilateral symmetrical neurons assoc iated with the optic lobes and the arachnid ''central body'' were anal ysed in detail, comparing the harvestman R. triangularis and the spide rs Brachypelma albopilosa (Theraphosidae), Cupiennius salei (Lycosidae ), Tegenaria artrica (Agelenidae), Meta segmentata (Metidae) and Nephi la clavipes (Araneidae). Sixteen neurons have been identified that dis play markedly similar axonal pathways and arborization patterns in all species. These neurons are considered homologues in the opilionid and the araneid brains. We presume that these putative phylogenetically p ersisting neurons represent part of the general morphological pattern of the arachnid brain.