Comparisons of the neurotoxic activity of the venom of several species of funnel web spiders (Atrax).

A bioassay has been developed to allow comparison of the neurotoxic activity of the venom of individuals of the four most common species of funnel web spiders (Atrax species). In the absence of purified Atrax neurotoxin, the stimulatory action of the venom on skeletal muscle from the cane toad, Bufo marinus, was compared with that of known concentrations of acetylcholine. Several experiments to validate the assay were performed, then venom samples from both male and female spiders were assayed. It was found that individual female spiders of all Atrax species normally secreted several times as much venom as male spiders, but its neurotoxicity was extremely variable and generally much lower. Both sexes tended to secrete more potent venom in summer than in other seasons. Both also showed some decrease in venom volumes and potencies if repeatedly milked at short intervals. All four Atrax species were found to have approximately equal levels of neurotoxic activity.