Joan Cartan-Hansen, Host: Crayfish...Crawfish... Crawdad... Mudbug...

These are all names for a remarkable crustacean... one that shows how well an animal can adapt.

[MUSIC] Cartan-Hansen: University of Idaho professor of biology Alan Kolok finds crayfish endlessly fascinating.

Alan Kolok: I think the thing that really interested me about these animals is both their consistency over time in that this fundamental body form is millions of years old and it has, hasn't really changed all that much.

Cartan-Hansen: Crayfish look a lot like their cousins: lobster, shrimp and crab.

They have an exoskeleton, a hard shell that protects their body.

And they are perfectly adapted for their muddy, water environment.

Kolok: He has really long antennae, but look at his eyes.

His eyes are really small.

Why is that?

Well, where this animal lives, sight isn't as important as touch.

So, this animal knows its environment by, through its antennae and what it can touch as much, if not even more so than what it can see.

That's one thing.

The second thing, look at these big claws.

Look at these giant claws this animal has.

You might think that an animal like this would use those claws to defend himself against predators, things like large fish or otters or mink, but that's not really the case.

What they really use these, these claws for is to fight each other.

Cartan-Hansen: It's a way to attract a mate in the same way big horned sheep fight over their mates.

(clashing sounds) Crayfish are part aquatic, in that is they swim, but they can also walk around.

And they have a special adaptation to help them move quickly.

Kolok: Look at the size of this tail.

The animal has a large thick tail with big swimming fins, these paddles at the end.

So, this animal's a powerful swimmer.

It's not a great walker, but he's a really powerful swimmer.

Now the interesting thing about this animal and how he swims.

Look at the way that his tail bends.

His tail is going to move in this direction like that.

So, this animal is going to be propelled through the water backwards.

Cartan-Hansen: Walking and swimming backwards means a crawfish can keep its eyes on whatever is trying to eat it.

And a lot of things want them for lunch.

Crayfish are on the bottom of the food chain, an important food source for many animals.

And because of their unique place in the ecosystem, crayfish are very important to scientists like Kolok.

Kolok: I'm interested in some chemicals, some water pollutants that actually find their way into that sediment into that bottom water.

Well, this animal lives in that sediment, therefore if you were to look at this animal and to take out its tail for example.

And run it out on the appropriate type of analytical machine, what you will actually find, you will be able to see the signature or those water pollutants in the animal.

Cartan-Hansen: Scientists at the Idaho water resources research institute at the University of Idaho use crayfish to inspect the health of the miles of rivers and lakes in north Idaho.

These blue sparkly waters hide a history of mining that left behind all sorts of chemicals and heavy metals.

Now pollutants are also released into the air when we burn things.

And they eventually fall back into the water.

Pollutants also come from agricultural activity and from urban development.

And one of Kolok's biggest concern is the pollutant, mercury.

Kolok: The mercury is not going to stay in the water.

It's actually going to move either into an animal, either into the tissues of an animal, such as a crayfish, or it's going to move into the sediment.

Cartan-Hansen: So, it's kind of a chain reaction.

Crayfish live and eat things in the sediment.

Fish come along and eat lots of crayfish.

And all that mercury in the crawfish then gets concentrated into the fish, which humans consume when they eat the fish.

Kolok: And that can start to be a problem because mercury is damaging to nerve tissue, to your brain, to your central nervous system.

Well, if we can take the tail out of this animal and look for chemicals, and if there are chemicals that are toxic or poisonous in this animals' tail, it tells us something about that environment.

It tells us something about what the water and what the sediment, um, looks like from the perspective of water pollution.

Cartan-Hansen: Kolok says citizen scientists around the region help him in his work.

They find crayfish in various water bodies and send them to his lab for analysis.

Even young people can learn how to help.

Kolok and his family started learning about animals when they were young, sailing along the eastern seaboard.

And he has a piece of advice for kids who might want to be a biologist someday.

Kolok: Ask the questions of why does this animal look like this?

What's the point?

Why, why is it the color that it is?

Why does it have as many legs that it does?

Remain curious and don't be embarrassed by that or, uh, or, um, or standoffish about it?

Animals and nature is, is fundamentally cool and fundamentally interesting.

And keep your inquisitiveness and ask those questions because trust me, I can tell you this from personal experience, it will pay off for you in the long run relative to a profession.

Cartan-Hansen: If you want to learn more about animal adaptations, check out the science trek website.

You'll find it at science trek dot org.

[MUSIC] ANNOUNCER: Presentation of Science Trek on Idaho Public Television is made possible through the generous support of the Laura Moore Cunningham Foundation, committed to fulfilling the Moore and Bettis family legacy of building the great state of Idaho.

By the Idaho National Laboratory, mentoring talent and finding solutions for energy and security challenges, by The Friends of Idaho Public Television and by the Corporation for Public Broadcasting.