Lizards are pretty familiar reptiles but they still do a lot of weird stuff.
They can climb vertical glass walls, change color,
even breathe underwater using tiny bubbles of air trapped on their heads,
like little reptilian scuba divers.
One species spends most of its life as an egg,
another spreads its ribs out to glide through the air,
and a third can run on two legs across water.
Some of them are really big, or incredibly photogenic, or just very strange-looking.
And some of them aren’t.
Picture the most standard-looking gray or brown lizard that a kid could catch in their backyard.
If that kid is in North or Central America, chances are good
that they have caught some species of fence lizard.
And if they’re in the western U. S., it might be a western fence lizard,
also known as a blue-belly, for its blue belly.
While these guys might not be the most glamorous lizards around, for the blue-belly,
it’s what’s on the inside that really makes it a bizarre beast.
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Back in the mid-1980s, researchers in northern California started investigating the relationship
between blue-bellies, western black-legged ticks, and Lyme disease.
Lyme disease can be caused by a couple of different species of bacteria in the genus Borrelia.
It’s transmitted to people through the bites of infected ticks
and the ticks pick up the infection from animal hosts they feed on early in their life cycle.
The researchers knew that blue-bellies were a primary host of the immature form of these ticks
and that the ticks were the main transmitters of Lyme disease in the region.
And blue-bellies are just everywhere out there.
They’re one of the most abundant lizards in the area.
They live in all kinds of different habitats, from sea level to over 2700 meters,
and ticks love to snack on them.
But people getting Lyme disease in the western U. S. is pretty uncommon.
And this seems weird.
California’s got the bacterium that causes Lyme, the ticks that carry it,
and plenty of hosts for all the ticks.
So where are the human cases?
Fast forward to the 1990s, when a professor working on tick-borne diseases at UC Berkeley noticed something odd.
The ticks that he removed from blue-bellies never seemed to be infected with Lyme.
Now, this struck him as strange because
he’d been one of the guys who’d originally found the Lyme-causing bacterium in ticks
in California in the first place.
And some later research had shown that immature ticks were even more likely to be infected
than the adult ticks he’d been looking at.
He figured that either something was getting rid of the Lyme-causing bacteria
inside the immature ticks when they turned into adults
or that something about feeding on the lizards was curing the ticks.
Now he’d shown before that it was almost impossible to experimentally infect blue-bellies with Lyme.
This meant that, while they are a major host for immature ticks,
they aren’t a host for the disease-causing bacteria.
So now, he set up some experiments to test his two hypotheses about why the bacteria were disappearing.
And what he found was that feeding on the lizards was what was getting rid of the bacteria!
Something in the lizard’s blood was actually curing the ticks of Lyme.
No fast forward again to 2000, when a new team of researchers, including that professor,
figured out what made the lizard’s blood deadly to the Lyme-causing bacteria.
It turns out, there’s a group of proteins that make up one part of the blue-belly’s
immune system that both keep the lizard from getting infected
AND when a tick sucks its blood, gets into the tick’s gut and kills the Lyme bacteria in there!
And we thought this might be part of why California doesn’t have all that many cases of Lyme disease,
all thanks to the bizarre ability hidden in the blood of the western fence lizard.
BUT, it might actually be a little bit more complicated than that,
because all living systems always are.
And this is especially true in the field of disease ecology, which studies how hosts,
pathogens, the environment, and evolution
interact with each other to influence diseases in populations.
In a study published in 2011, researchers experimentally removed the blue-bellies from one area,
to see if that would increase the Lyme disease risk to people.
They thought that having fewer lizards around would mean larval ticks would switch to feeding on other hosts
that were capable of being infected with Lyme, leading to more Lyme-infected ticks.
But it did not.
It looks like the majority of larval ticks in the area didn’t switch hosts,
they just completely failed at finding a host at all.
Not finding a host meant that the ticks couldn’t feed and complete their life cycle.
Another possibility is that some of the ticks did switch hosts.
But instead of switching to a mammal host that can carry the Lyme-causing bacteria,
they switched to a different lizard host, instead.
Like the blue-belly, the southern alligator lizard also has an immune system
that can take on Lyme and cure larval ticks.
They’re really good at camouflage though,
so the researchers weren’t able to catch them and count their ticks to find out.
Either way, it looks like fewer blue-bellies around resulted in fewer ticks overall,
which lowered the disease risk to people, at least in this one, short-term study.
So blue-bellies seem like they might be a bit of a double-edged sword.
While their blood does cure Lyme-infected ticks,
their presence means there can just be more ticks around, period.
But the question is, and I hope you’re asking it too,
is there a way to steal this super power from them to keep us from getting infected with Lyme?
Unfortunately, probably not,
because it’s not just a single thing in the western fence lizard’s immune system that keeps them healthy,
it’s a whole series of cascading reactions taking place within that system.
Ultimately, the immune system of the blue-belly is just one tiny complicated system
within a series of increasingly large and complicated systems,
like the ecosystem it lives in and the complex disease ecology of Lyme.
Which is kinda beautiful!
And being able to see how the blue-belly fits in as a small piece of this bigger picture
is part of what makes it, and all living things, bizarre beasts in their own way.
Bizarre Beasts is celebrating the second year of the pin club
and the one-year anniversary of having our own channel
by keeping the subscription window open from NOW until the end of July 11th!
Check out this lizard pin!
Sign up today and you’ll get this beautiful blue-belly pin in the middle of the month
and the pins after that around the time each new video goes up.
So either you’ll see an episode in the subscription box and then a pin in your mailbox,
or a pin in your mailbox and you’ll be like, “I gotta go watch Bizarre Beasts!”
Also we have new stickers!
And for those of you in the pin club, YES, there will be another blooper video!
As always, we’ll be sharing extra facts about this awesome lizard all month on Twitter @BizarreBeasts,
and on Instagram and Facebook @BizarreBeastsShow!
And profits from the pin club go to support our community’s efforts
to decrease maternal mortality in Sierra Leone.
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