Name: 澳洲漏斗網蜘蛛 (Australian funnel-web spider)
Uploaded: 2021-01-14T05:58:49.000Z
Duration: 13 min 58 s
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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

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

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