The distribution of monoamine oxidase and biogenic monoamines in the central nervous system of spiders (Arachnida: Araneida)

The distribution and activity patterns of monoamine oxidase and monoaminergic (formaldehyde-induced) fluorescence in the CNS of web-building and hunting spiders [web builders: Agelenidae (funnel-web spiders), Tegenaria derhami (Scopoli); Araneidae (orb-web spiders), Araneus sclopetarius (Clerck), A. marmoreus (Clerck) and Zygiella x-notata (Clerck); hunters: Lycosidae (wolf-spiders), Pardosa lugubris (Walkenaer), P. amentata (Clerck) and Trochosa spinipalpis (Cambridge); Salticidae (jumping spiders), Epiblemum scenicum (Clerck), (= Salticus scenicus Linne), Sitticus floricola (C.L. Koch) and Marpissa muscosa (Clerck) (= M. rumpfi (Scopoli)] were studied using histochemical methods. Enzyme activity occurred in the neuronal perikarya and in varying intensity in the structures of the neuropile mass, but only when dopamine, adrenaline [epinephrine] and noradrenaline [norepinephrine] were used as substrates. The optic centers of the spider brain normally exhibited relatively strong enzyme reactions when compared with the staining intensity of the rest of the nervous system. The neuronal cell bodies contained numerous granules of yellow-green fluorescence. Monoaminergic fluorescence of the neuropile was generally a weak green. The optic masses of the hunting spiders, the anterior bridge, several commissures of the ventral cord and the neural lamellae showed a slightly higher fluorescence intensity and single fluorescing granules. The presence of catecholamines in the spider nervous system is indicated.