The Sydney funnel-web spider (Atrax robustus) is a species of venomous mygalomorph spider native to eastern Australia, usually found within a 100 km (62 mi) radius of Sydney. It is a member of a group of spiders known as Australian funnel-web spiders. Its bite is capable of causing serious illness or death in humans if left untreated.
The Sydney funnel-web has a body length ranging from 1 to 5 cm (0.4 to 2 in). Both sexes are glossy and darkly coloured, ranging from blue-black, to black, to shades of brown or dark-plum coloured.
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TerrestrialTerrestrial animals are animals that live predominantly or entirely on land (e.g., cats, ants, snails), as compared with aquatic animals, which liv...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withThe Sydney funnel-web is medium to large in size, with body length ranging from 1 to 5 cm (0.4 to 2 in). Both sexes are glossy and darkly coloured, ranging from blue-black, to black, to brown or dark-plum coloured. The carapace covering the cephalothorax is almost hairless and appears smooth and glossy. Another characteristic are finger-like spinnerets at the end of their abdomen.The shorter-lived male is smaller than the female, but longer-legged. The average leg length for the spider in general is six to seven centimetres.
Distribution is centred on Sydney, extending north to the Central Coast and south to the Illawarra region, and west to the Blue Mountains in New South Wales.
The spider can be found in moist microhabitats, including under logs and foliage.
Sydney funnel-web spiders are mostly terrestrial spiders, favouring habitats with moist sand and clays.
They typically build silk-lined tubular burrow retreats with collapsed "tunnels" or open "funnel" entrances from which irregular trip-lines radiate over the ground. In some exceptions, which lack trip-lines but may have trapdoors, the silk entrance tube may be split into two openings, in a Y or T form. The spiders burrow in sheltered habitats where they can find a moist and humid climate; for instance under rocks, logs or borer holes in rough-barked trees. The long-lived female funnel-web spend most of the time in their silk-lined tubular burrow retreats. When potential prey, which includes insects, lizards or frogs, walks across the trip-lines, they rush out, subduing their prey by injecting their venom.
Males, recognised by the modified terminal segment of the palp, tend to wander during the warmer months of the year, looking for receptive females to mate with. This makes encounters with male specimens more likely as they sometimes wander into backyards or houses, or fall into swimming pools. The spiders can survive such immersion for up to twenty-four hours, trapping air bubbles on hairs around their abdomen. Sydney funnel-web spiders are mainly active at night, as typical day-time conditions would dehydrate them. During the day, they seek cover in cool, moist hideaways. After heavy rain, spider activity is increased as their burrows may be flooded.When threatened or provoked, funnel-web spiders will display aggressive behaviour, rearing up on their hind legs and displaying their fangs. When biting, the funnel-web spider maintains a tight grip on its victim, often biting repeatedly.
The lethal dose of venom in humans is not known. The lethal dose of venom from male Sydney funnel-web spiders for the crab-eating macaque (Macaca fascicularis) is 0.2 milligrams per kilogram (3.2×10−6 oz/lb). Higher figures were found for other experimental animals, such as 1.5 milligrams per kilogram (2.4×10−5 oz/lb) for two-day-old mice. The average venom yield for a male is 176 milligrams (2.72 gr). In doses like 5 mg / kg intravenously, Delta atracotoxin kills monkeys in 3–4 hours, the symptoms seen in monkeys were dyspnea, blood pressure fluctuations, culminating in severe hypotension, lacrimation, salivation, skeletal muscle fasciculation and death. Guinness World Records has ranked the Sydney funnel-web spider as the world's most venomous spider, defining the term "most venomous" as "having the venom most toxic to humans", although it had also previously given this title to the Brazilian wandering spider.
Sydney funnel-web spider venom contains a compound known as Delta-Atracotoxin, an ion channel inhibitor, which makes the venom highly toxic for humans and other primates. However, it does not affect the nervous system of other mammals. These spiders typically deliver a full envenomation when they bite, often striking repeatedly, due to their defensiveness and large cheliceral fangs. There has been no reported case of severe envenoming by female Sydney funnel-web spiders, which is consistent with the finding that the venom of female specimens is less potent than the venom of their male counterparts.In the case of severe envenomation, the time to onset of symptoms is less than one hour, with a study about Sydney funnel-web spider bites finding a median time of 28 minutes. This same study revealed that children are at particular risk of severe Sydney funnel-web spider envenoming, with 42% of all cases of severe envenoming being children.
There is at least one recorded case of a small child dying within 15 minutes of a bite from a funnel-web.
