Chuck Bednar for redOrbit.com – Your Universe Online
An in-depth analysis of the black widow spider’s genetics, protein expression and venom content has revealed exactly how and why these deadly arachnids have become so extremely toxic.
As part of the research, Dr. Jessica Garb of the University of Massachusetts, Lowell and a team of colleagues from the US and the UK have discovered that the most potent neurotoxins present in the venom of the black widow are known as latrotoxins.
Those latrotoxins, which were named after the group of widow spiders known as Latrodectus, include “a devastatingly debilitating chemical” known as alpha-latrotoxin, the researchers said in a statement Tuesday. This substance can hijack the body’s own internal communication system by affecting the electrical and chemical signaling capabilities of its victim’s nervous system.
“If you got bitten by a black widow, alpha-latrotoxin would travel to the pre-synaptic regions of your neurons: this is the juncture right between the synapse of one neuron and your muscle cells or another neuron, and it inserts itself into the membrane,” said Garb, who presented her team’s research at the annual conference of the Society of Integrative and Comparative Biology.
“This causes all of the neuron’s vesicles to dump out their neurotransmitters. And that’s really what’s painful,” she added. In other words, this chemical causes a victim’s nerve cells to release off of their chemical signals at once, causing an immense amount of pain in the process.
Alpha-latrotoxin has long been the topic of study by spider biologists and neuroscientists, as it can help them learn more about how neurons function. Until recently, the latrotoxins were believed to be a small group of proteins. However, Garb’s research had revealed that they are actually a far larger group than expected, and are even found in the common house spider.
While house spiders are related to the black widows, their venom is typically believed not to be toxic to people. The difference in the potency of their respective poisons, the researchers said, is likely a case of the production of the toxins, but not the genetic ability to do so.
“It’s not just about the numbers of these latrotoxins, but their relative expression,” said Garb. Even though common house spiders possess the genes for multiple latrotoxins, they appear to produce them at far lower levels in their venom in comparison to black widows. However, the researchers explained that genetics still play a key role in the evolution of venom.
“The house spider genome is a great resource for us, because we can now get the full landscape of what’s in the genome of one of these spiders,” Garb explained. “There has been a lot of lineage-specific evolution of this latrotoxin family, and the set of latrotoxins in house spider venom appears to be quite distinct from those in black widow venoms.”
By studying more than one species of spider, the study authors were able to compare latrotoxin genes among species that, while closely-related, vary in venom functionality and toxicity. They found that the latrotoxin genes among spiders, while clearly related, are highly divergent.
Essentially, they found that instead of having latrotoxin genes that have evolved slowly over an extended period of time, the black widows have genes that have been duplicating and changing over a relatively short period of time. This has contributed to the potency of their venom.
The sudden appearance of multiple latrotoxins probably allowed the spiders to pursue a variety of different types of prey, including small mammals and reptiles that it otherwise would not have been able to eat, the study authors said. It is even possible that the webs of black widows changed along with their venoms, becoming strong enough to trap these larger types of prey.
By milking venom from the black widow spiders, Garb and her associates also found that it is actually made up of several different types of toxins. In addition to neurotoxins, the venom also contained chemicals that helped those toxins reach their targets within the victim’s body.
—–
Follow redOrbit on Twitter, Facebook, Instagram and Pinterest.
Comments