Sydney funnel-web spider
Encyclopedia
The Sydney funnel-web spider, Atrax robustus, is an Australian funnel-web spider usually found within a 100 km (62.1 mi) radius of Sydney, New South Wales, Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

Description

Sydney funnel-webs are medium to large in size, with body length ranging from 2 to 7 cm (0.78740157480315 to 2.8 in). They 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. The shorter-lived males are smaller than females but longer legged.

It is one of three species of the genus Atrax in the family Hexathelidae
Hexathelidae
The spider family Hexathelidae, the only family in the super-family Hexatheloidea, is one of two families of spiders known as funnel-webs...

. The common name of the species is shared by other members of the genus Hadronyche
Hadronyche
Hadronyche is a genus of venomous spiders found in Australasia. Some species are termed Australian funnel-web spider, being highly venomous members of the Hexathelidae family...

, but it and the northern tree funnel-web are the only Australian funnel-web spiders known to have inflicted fatal bites to humans.

Behaviour

The spider can be very aggressive when provoked. The long-lived female funnel-webs spend most of the time in their silk-lined tubular burrow retreats. Males, recognized by the modified terminal segment of the palp
Pedipalp
Pedipalps , are the second pair of appendages of the prosoma in the subphylum Chelicerata. They are traditionally thought to be homologous with mandibles in Crustacea and insects, although more recent studies Pedipalps (commonly shortened to palps or palpi), are the second pair of appendages of the...

, tend to wander during the warmer months of the year looking for receptive females to mate
Sexual intercourse
Sexual intercourse, also known as copulation or coitus, commonly refers to the act in which a male's penis enters a female's vagina for the purposes of sexual pleasure or reproduction. The entities may be of opposite sexes, or they may be hermaphroditic, as is the case with snails...

 with. They are attracted to water and hence are often found in swimming pools, into which they often fall while wandering. The spiders can survive such immersion for up to twenty-four hours and can deliver bites when removed from the water.

They 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 burrow may be in the hollow of a tree trunk or limb, many metres above ground level.

Distribution

Distribution is primarily south of the Hunter River to the Illawarra region, and west to the Blue Mountains in New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...

. However, unconfirmed reports contradicting Gray (1987) claim that the Sydney funnel-web spider has been found as far away as Canberra
Canberra
Canberra is the capital city of Australia. With a population of over 345,000, it is Australia's largest inland city and the eighth-largest city overall. The city is located at the northern end of the Australian Capital Territory , south-west of Sydney, and north-east of Melbourne...

, from Sydney
Sydney
Sydney is the most populous city in Australia and the state capital of New South Wales. Sydney is located on Australia's south-east coast of the Tasman Sea. As of June 2010, the greater metropolitan area had an approximate population of 4.6 million people...

, and even Gloucestershire
Gloucestershire
Gloucestershire is a county in South West England. The county comprises part of the Cotswold Hills, part of the flat fertile valley of the River Severn, and the entire Forest of Dean....

 in England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...

.

Venom

Funnel-web spider venom contains a compound known as atracotoxin, a highly toxic ion channel inhibitor
Channel blocker
A channel blocker or ion channel blocker is a type of drug which binds inside the pore of a specific type of ion channel and blocks the flow of ions through it, resulting in an alteration of the electrochemical gradient of the cell membrane of neurons and therefore a change in...

. These spiders typically deliver a full envenomation when they bite, often striking repeatedly, due to their aggression and large chitin
Chitin
Chitin n is a long-chain polymer of a N-acetylglucosamine, a derivative of glucose, and is found in many places throughout the natural world...

ous cheliceral fangs. For this reason, people are strongly advised not to approach them. There is at least one recorded case of a small child dying within 15 minutes of a bite from a Sydney funnel-web spider; that event occurred before the development of an antivenom. For very small children the amount of venom dispersed throughout the body is many times the concentration in an adult. Since the antivenom was developed in 1980, there have been no recorded fatalities from Sydney funnel-web spider bites.
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