ACTIONS OF SPIDER VENOMS ON INSECT NERVE AND MUSCLE (ARANEUS DIADEMATUS, STEATODA BIPUNCTATA, TEGENARIA GIGANTEA, LYCOSA CAROLINENSIS)

Available from UMI in association with The British Library. Requires signed TDF.; Effects of venoms from four spider species (representing families with differing predation strategies) were studied on insect nervous systems. Araneus diadematus, Steatoda bipunctata use orb and random 3D webs respectively, to restrain prey prior to silk wrapping and venom injection. Tegenaria gigantea uses sheet webs solely to locate prey, which following capture are subdued by venom. Captive Lycosa carolinensis (uses no web) captures prey by grasping them with chelicerae (equivocal venom usage).; Venom was extracted by "milking" or homogenization of venom apparatus. All venoms affected Musca domestica "righting ability": relative ED{dollar}sb{lcub}50{rcub}{dollar}'s S. bipunctata {dollar}gg{dollar} A. diadematus {dollar}>{dollar} T. gigantea {dollar}>{dollar} L. carolinensis.; Injection of larval Calliphora erythrocephala with each venom induced rapid paralysis. A. diadematus, T. gigantea venoms reduced body wall muscle tone (flaccid paralysis); S. bipunctata, L. carolinensis venoms increased tone (tetanic paralysis).; Each venom increased spontaneous neural activity in Periplaneta americana ventral nerve cord. Heat stable A. diadematus, T. gigantea venom fractions produced, in Schistocerca gregaria retractor unguis (Ru.) muscle, reversible, use-dependent twitch amplitude reduction. In extensor tibiae muscle whole venom caused reductions in amplitude and frequency of evoked excitatory post synaptic potentials (EPSP) and miniature EPSPs respectively and block of ionophoretic glutamate potentials. Thus these venoms contain components which induce use-dependent postsynaptic neuromuscular block which probably synergise with elevated efferent neural activity to facilitate nerve-muscle block.; In contrast, heat labile S. bipunctata venom fraction caused use-independent Ru. muscle contractions. Heat stable L. carolinensis venom fractions either reduced twitch amplitude ({dollar}<{dollar}10kda.) or produced use-independent muscle contractions (10-30kda.). Whole venoms, whilst not affecting ionophoretic glutamate potentials, elicited depolarisation-dependent reductions in EPSP amplitude and increases in miniature EPSP amplitude and frequency. S. bipunctata venom caused nerve terminal disruption and subsequent degeneration of Ru. muscle. These results suggest that the venoms enhance neurotransmitter release.; Links between predation and venom action were not seen. Results are discussed in relation to actions of venoms and toxins from other species of spider.