The potent cocktail of toxins in the venom of one of the world’s deadliest spiders seems to vary depending on the context.
A new analysis of how funnel-web spiders produce their venom shows that factors such as the spider’s heart rate and defensiveness may play a role in the proportions of chemicals delivered to the tips of the spiders. fangs of an angry arachnid.
Why do we want to know? Because funnel-web spider venoms are complex mixtures with a range of potential applications, such as natural pesticides and pharmaceuticals – not to mention the antivenom used to treat deadly spider bites. Understanding why funnel-webs produce these mixtures may help with better milking and utilization of venom and help us understand venom function.
“Funnel-webs have the most complex venom in the natural world, and they are valued for the therapeutic and natural bioinsecticides that may be hidden in their venom molecules,” explains biologist Linda Hernández Duran of James Cook University in Australia.
“Knowing more about how they are made is a step toward unlocking this potential.”
We’ve done a lot of research on funnel-web venom, which is fatal only to its prey insects and, due to some strange quirk of evolution, primates.
Australian funnel-web spiders are famous for being the deadliest (to humans, anyway) in the world, although you may be comforted to know that, though 30 to 40 people are bitten every year, only the male Sydney funnel-web has killed humans, and there have been no funnel-web deaths since antivennom became available in 1981.
However, while much work has been done to understand the molecular complexity of the venom, these studies do not take into account the behavior, physical state, and environment of the spiders. So Hernández Duran and his colleagues began to investigate.
They collected specimens of four species of Australian funnel-web spiders – Border Ranges (Hadronyche valida), Darling Downs (Hadronyche infensa), southern tree habitat (Hadronyche cerberea), and Sydney (Atrax robustus) funnel-webs. These spiders were subjected to some annoying tests.
Tests assessed crowding, defending, climbing, and general active behavior in three different contexts. The first is predation, which scientists simulate by blowing air or prodding the spiders with tweezers. The second is hanging out with another spider of the same species. And the third is the exploration of a new territory.
During these tests, the researchers “mapped [the spiders’] behavior and measured their heart rate using a laser monitor to establish a proxy value for their metabolic rate. We then collected their venom and analyzed it using a mass spectrometer,” said Hernández Duran.
For the three species, there seems to be no relationship between their behavior and heart rate and the composition of their venom. However, the scientists noticed a difference for a spider: a higher heart rate and defensiveness in the Border Ranges funnel-web seems to be related to a different composition of the venom.
The fact that the three other species did not show the same relationship between venom composition and physical factors indicates that these associations may be species specific. We just don’t know what the associations might be for other species.
The research also made another connection. We know that venom production and the aggressive displays made by cranky funnel-webs have metabolic costs. The team’s work suggests that funnel-web spiders may make behavioral changes to compensate, increasing their metabolic rate to produce venom and reducing their movement when under threat.
Other strategies may include adjusting the number of bites, modulating the amount of venom, and making aggressive displays without delivering a venomous bite.
The results, the researchers say, could be helpful for the production of antivenom and the study of bioactive components found in funnel-web venoms.
“We show for the first time how specific components of venom are related to specific behavioral and physiological variables and show that these relationships are context dependent,” said Hernández Duran.
“We gained some important insights for further exploring and understanding the ecological role of the toxin.”
The research was published in PLOS ONE.
