Toxins
There are many different toxins in the venom of Atrax and Hadronyche spiders. Collectively, these spider toxins are given the name atracotoxins (ACTX), as all these spiders belong to the subfamily Atracinae. The first toxins isolated were the δ-ACTX toxins present in the venom of both A. robustus (δ-ACTX-Ar1, formerly known as robustoxin or atracotoxin) and H. versuta (δ-ACTX-Hv1a, formerly known as versutotoxin). Both these toxins produce the same funnel-web envenoming syndrome in monkeys as that seen in humans, suggesting that they are responsible for the physiological effects seen with crude venom.
These toxins are thought to operate by opening sodium channels. They are presynaptic neurotoxins that (via sodium channels) induce spontaneous, repetitive firing of action potentials in autonomic and motor neurons and inhibit neurally mediated transmitted release resulting in a surge of endogenous acetylcholine, noradrenaline and adrenaline.
Although extremely toxic to primates, the venom appears to be fairly harmless to many other animals. It has been suggested that these animals may be resistant to the venom's effects due to the presence of IgG, and possibly cross-linked IgG and IgM inactivating factors in their blood plasma that bind to the toxins responsible and neutralise them.
The female venom was thought to be only about a sixth as potent to humans as that of the male The bite of a female or juvenile may still be serious; however, considerable variability occurs in venom toxicity between species, together with assumable degrees of inefficiency in the method of venom delivery.
Read more about this topic: Australian Funnel-web Spider, Medical Significance