The venom of the deadliest spider in the world varies according to its mood

Scientists have found that the venom of funnel-web spiders can be different depending on their heart rate and defensive behavior.

Australian funnel-web spiders are considered the most venomous in the world. They possess extremely poisonous venom, resulting in the death of a human in just fifteen minutes. According to researchers, the substance it injects its victims could evolve according to certain conditions. Their observations have been available since May 22 in an article in the journal Plos One, spotted by Science Alert.

Heart rate and defensive behavior

A team from the Australian Institute of Tropical Health and Medicine at James Cook University in Australia studied the venom of four species of funnel-web spider : the true funnel-web spider (Hadronyche valida),  Darling Downs funnel-web spider, (Hadronyche infensa ), Southern tree-dwelling funnel-web spider (Hadronyche cerberea) and The Sydney funnel-web spider (Atrax robustus). The insects were subjected to several tests where their reaction and their heart rate were evaluated. They were, for example, pushed with tweezers or inflated with air, lists a press release from the university. At the end of the experiments, their venom was collected and then analyzed.

The researchers noticed that the composition of the venom of the true funnel-web spider was different depending on their heart rate and their state of defense. "With the true funnel-web spider, expression of certain venom components was associated with heart rate" and defensive behavior, said lead author Dr. Linda Hernández Duran. The other species did not demonstrate this, suggesting that particular associations may be species-specific.”

Reduce metabolic costs

The study suggests that these spiders may adopt strategies to reduce metabolic costs. "Animals with high metabolic rates are believed to be aggressive, active, and more aggressive in obtaining resources to maintain their metabolism," the authors write in the paper. In spiders, venom plays an important role in predation and predator deterrence (...) However, the use of venom and the display of aggressive behaviors can incur metabolic costs.”

The authors believe that spiders may increase their metabolic rate when using venom and to reduce their movement when faced with a threat. They could also reduce metabolic costs by adjusting the number of bites or by modulating the quantity of venom. "For example, [they] can estimate the amount of venom available in their venom glands, which could help them select prey, and they can also modulate venom expenditure under different threat levels."

For scientists, this data could be taken into account in the design of anti-venom, but also for the discovery of new drugs. "Funnels contain the most complex venoms in the natural world, and they are valued for the natural therapeutics and bioinsecticides that are potentially hidden within their venom molecules. Knowing more about how they are produced is a step towards releasing of this potential."

Types of venemous spiders

There are several types of venomous spiders, some of which are more dangerous than others. Here are some examples :

Black Widow Spider : This spider is one of the most venomous spiders in the world and is found on every continent except Antarctica. It is identified by its shiny black body and distinct red hourglass-shape on the underside of the abdomen.

Brown Recluse Spider : Also known as the violin spider, this spider is most commonly found in the Midwestern and southern states of the United States. It is brown in color with a characteristic dark violin-shaped marking on its head and has six equal-sized eyes.

Widow Spiders : The widow spiders (genus Latrodectus), such as the black widow, redback spider, and katipō, carry a neurotoxic venom which can cause a set of symptoms known as Latrodectism. They are large, shiny house spiders with relatively spindly legs and deep, globular abdomens. Mature females have dark and shiny abdomens with one or several red spots, either above and/or below.

Sac Spiders : These spiders have venom that can cause skin-killing wounds. They are usually found in South Africa.

False Widow Spiders : This genus, Steatoda, has yet to be proven to possess a venom of medical significance. They are often confused with the brown recluse spider.

Hobo Spider : This spider can be recognized by its light to medium brown coloring and the multiple chevron patterns on its abdomen pointing toward their head. They are often confused with the brown recluse spider, but the brown recluse is much more dangerous to humans.

Chilean Recluse Spider : This spider is among the recluse spiders and is found in Chile. Its venom can cause necrosis.

Katipo Spider : This spider is found in New Zealand and is a type of widow spider. Its venom can cause muscle pain, spasms, and breathing difficulties.

Brown Widow Spider : This spider is found throughout the world and is identified by the pattern of red coloration on the underside of its abdomen. It is usually found in workplaces containing undisturbed areas such as woodpiles, under eaves, fences, and other areas where debris has accumulated.

In Florida, only two main types of venomous spiders occur: widow spiders and recluse spiders. Three species of widow spiders are native to Florida, and a single species of recluse spider is found in the state.