Atracinae, commonly known as Australian funnel-web spiders, is a subfamily of spiders in the
funnel-web spider family Hexathelidae. Atracinae consists of three genera: Atrax, Hadronyche,
and Illawarra. The subfamily includes species with medically significant venom, six species
of which have severely envenomed human victims. The bite of Atrax robustus is potentially
deadly, but there have been no fatalities since the introduction of modern first aid
techniques and antivenom. The subfamily contains 35 species. All members of the subfamily are
native to Australia.
Description These spiders are medium-to-large in size,
with body lengths ranging from 1 cm to 5 cm. They are darkly coloured, ranging from black
to blue-black to plum to brown, with a glossy, hairless carapace covering the front part
of the body. Like the related diplurid spiders, some hexathelids have relatively long spinnerets;
this is especially true of A. robustus. Males have a large mating spur projecting from the
middle of their second pair of legs. Like other Mygalomorphae —an infraorder
of spiders that includes the tropical tarantulas —these spiders have fangs which point straight
down the body and do not point towards each other. They have ample venom glands that lie
entirely within their chelicerae. Their fangs are large and powerful, capable of penetrating
fingernails and soft shoes. Funnel-webs make their burrows in moist, cool,
sheltered habitats—under rocks, in and under rotting logs, some in rough-barked trees.
They are commonly found in suburban rockeries and shrubberies, rarely in lawns or other
open terrain. A funnel-web's burrow characteristically has irregular silk trip-lines radiating from
the entrance. Unlike some related trapdoor spiders, funnel-webs do not build lids to
their burrows. The primary range of the Australian funnel-web
spiders is the eastern coast of Australia, with specimens found in New South Wales, South
Australia, Victoria, and Queensland. The only Australian states or territories without funnel-webs
are Western Australia and the Northern Territory. Medical significance
Six species have severely envenomed human victims, including the C funnel web, northern
tree funnel web, southern tree funnel web, Blue Mountains funnel web, Darling Downs funnel
web and the Port Macquarie funnel web. Australian funnel-webs are one of the most dangerous
groups of spiders in the world and are regarded by some to be the most deadly, both in terms
of clinical cases and venom toxicity. Examination of bite records has implicated
wandering males in most if not all fatal funnel-web bites to humans. Adult males, recognised by
the modified terminal segment of the palp, will defend themselves vigorously if they
feel threatened and tend to wander during the warmer months of the year looking for
receptive females for mating. 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
several hours and can deliver a bite when removed from the water. They also show up
in garages and yards in suburban Sydney. Contrary to a commonly held belief, no funnel-web spider
is able to jump, although they can run quickly. While some very venomous spiders may give
dry bites, these spiders do so much less frequently. An inefficient mode of delivery and interrupted
contact are also possible causes of low volume delivery. It has been claimed that approximately
10% to 25% of bites will produce significant toxicity but the likelihood cannot be predicted
and all should be treated as potentially life-threatening. Funnel-webs are not normally aggressive but
will defend themselves vigorously if frightened or threatened. During an attack the funnel-web
spider generally maintains a tight grip on its victim and bites repeatedly, making it
an especially traumatic experience for humans who are bitten and increasing the risk of
severe envenomation. There have been 27 recorded deaths in Australia
in the last 100 years from spider bites. Bites from Sydney funnel-web spiders have caused
thirteen deaths. In all cases where the sex of the biting spider could be determined,
it was found to be the male of the species. Most victims were young, ill or infirm. One
member of the genus Hadronyche, the northern tree funnel-web has also been claimed to cause
fatal envenomation but, to date, this lacks the support of a specific medical report.
Assays of venom from several Hadronyche species have shown it to be similar to Atrax venom.
Toxins There are many different toxins in the venom
of Atrax and Hadronyche spiders. Collectively, these spider toxins are given the name atracotoxins,
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 and H. versuta. 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 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.
Symptoms Envenomation symptoms observed following bites
by these spiders are very similar. The bite is initially very painful, due to the size
of the fangs penetrating the skin. Puncture marks and local bleeding are also usually
visible. If substantial envenomation occurs, symptoms will generally occur within minutes
and progress rapidly. Early symptoms of systemic envenomation include
goose bumps, sweating, tingling around the mouth and tongue, twitching, salivation, watery
eyes, elevated heart rate and elevated blood pressure. As systemic envenomation progresses
symptoms include nausea, vomiting, shortness of breath, agitation, confusion, writhing,
grimacing, muscle spasms, pulmonary oedema, metabolic acidosis and extreme hypertension.
The final stages of severe envenomation include dilation of the pupils, uncontrolled generalised
muscle twitching, unconsciousness, elevated intracranial pressure and death. When death
occurs it is generally as a result of progressive hypotension or possibly elevated intracranial
pressure consequent on cerebral oedema. The onset of severe envenomation can be rapid.
In one prospective study, the median time to onset of envenomation was 28 minutes, with
only two cases having onset after 2 hours. Death may occur within a period ranging from
15 minutes to three days. Treatment
Due to the severity of symptoms, and the speed with which they progress, in areas where these
spiders are known to live all bites from large black spiders should be treated as though
they were caused by a funnel-web spider. First aid treatment for a suspected funnel-web spider
bite consists of immediately applying a pressure immobilisation bandage; a technique which
consists of wrapping the bitten limb with a crepe bandage, as well as applying a splint
to limit movement of the limb. This technique was originally developed for snakebites but
has also been shown to be effective at slowing venom movement and preventing systemic envenomation
in case of funnel-web spider bite; there is evidence to suggest that periods of prolonged
localisation may slowly inactivate the venom. Emergency medical treatment should be sought
as soon as possible. It is important that the pressure immobilisation bandage not be
removed prematurely; it should remain in place until intravenous access has been established,
adequate medical monitoring is in place and a supply of antivenom is available. A patient
who is not displaying any symptoms of systemic envenomation may deteriorate rapidly when
the bandage is removed. Further supportive care may be necessary,
but the mainstay of treatment is antivenom. Antivenom is raised against male Atrax robustus
venom but appears to be effective for all species of funnel web spiders. Funnel-web
antivenom has also been shown to reverse the in vitro effects of Eastern Mouse spider venom.
Prior to the introduction of antivenom, envenomation resulted in significant morbidity and mortality.
The purified rabbit IgG antivenom was developed in 1981 through a team effort led by Dr Struan
Sutherland, head of immunology at the Australian Commonwealth Serum Laboratories in Melbourne.
Fortunately, the antivenom is fast-acting and highly and globally effective. Antivenom
therapy has shortened the course of envenomation: prior to antivenom availability, the average
length of hospital treatment for severe bites was about 14 days. Today, antivenom-treated
patients are commonly discharged from hospital within 1 to 3 days. There have been no known
deaths since it became available. Species
The subfamily includes the following genera and species. Including their common names
and distribution. Atrax O. P.-Cambridge, 1877
Atrax robustus O. P.-Cambridge, 1877 — Sydney, Blue Mountains, Illawarra, Hunter New South
Wales Atrax yorkmainorum Gray, M.R., 2010 — Australian
Capital Territory and Riverina Atrax sutherlandi Gray, M.R., 2010 — Far
south coast of New South Wales and east Gippsland, Victoria
Hadronyche L. Koch, 1873
Hadronyche alpina Gray, M.R., 2010 — Kosciuszko National Park, New South Wales to Brindabella
Range, Australian Capital Territory Hadronyche adelaidensis — South Australia
Hadronyche annachristiae Gray, M.R., 2010 — Kerewong and Lorne State Forests, New
South Wales Hadronyche anzses Raven, 2000 — Queensland
Hadronyche cerberea L. Koch, 1873 — New South Wales
Hadronyche emmalizae Gray, M.R., 2010 — New South Wales
Hadronyche eyrei — South Australia Hadronyche flindersi — South Australia
Hadronyche formidabilis — Queensland, New South Wales
Hadronyche infensa — Queensland, New South Wales
Hadronyche insularis — Solomon Islands Hadronyche jensenae Gray, M.R., 2010 — Gippsland,
Victoria Hadronyche kaputarensis Gray, M.R., 2010 — Endemic
to Mount Kaputar Hadronyche levittgreggae Gray, M.R., 2010
— Hawkesbury River region, New South Wales Hadronyche lynabrae Gray, M.R., 2010 — New
South Wales Hadronyche macquariensis Gray, M.R., 2010
— New South Wales Hadronyche marracoonda Gray, M.R., 2010 — New
South Wales Hadronyche mascordi Gray, M.R., 2010 — New
South Wales Hadronyche meridiana Hogg, 1902 — Victoria
Hadronyche modesta — Victoria Hadronyche monaro Gray, M.R., 2010 — New
South Wales Hadronyche monteithi Gray, M.R., 2010 — Border
Ranges, Killarney, Queensland Hadronyche nimoola Gray, M.R., 2010 — New
South Wales Hadronyche orana Gray, M.R., 2010 — New
South Wales Hadronyche pulvinator — Tasmania
Hadronyche raveni Gray, M.R., 2010 — Conondale Range, Queensland
Hadronyche tambo Gray, M.R., 2010 — Gippsland, Victoria
Hadronyche valida — Queensland, New South Wales
Hadronyche venenata — Tasmania Hadronyche versuta — New South Wales
Hadronyche walkeri Gray, M.R., 2010 — New South Wales
Illawarra Gray, M.R., 2010
Illawarra wisharti Gray, M.R., 2010 — Illawarra region, New South Wales
Footnotes
External links Arachnology Home Pages: Araneae
Arachnology Home Pages: Atrax Platnick, N.I. 2003. World Spider Catalog
Funnel-web spider info Information, distribution and pictures of
A. robustus Australian Mygalomorphae or primitive spiders