Probing Platypus Evolution

(comical synthesized music)

NARRATOR: They're extremely awkward on land...

And not exactly graceful in the water.

But there's something endearing about these egg-laying mammals.

Platypuses can only be found in the rivers, streams, and lakes

along the East Coast of Australia.

But they range as far North as Northern Queensland, all the way down

to the Southern island of Tasmania.

That's quite a range for these little creatures.

But there are gaps between populations.

Large tracts of land between the rivers and lakes

make it difficult for the platypuses to migrate from one area to another.

Researchers believe it's possible

that isolated pockets of animals could have evolved differently,

could even be separate subspecies.

The interesting things about platypus are that, as you come up the coast from Tasmania,

they get smaller.

As well as that, their body size is actually less in some of the Northern ones,

so the maximum weight for one in this area

is somewhere in the region of a kilogram, about two and a half pounds.

Whereas they're around about three times that weight in Tasmania.

NARRATOR: Stephen Kolomyjec from James Cook University

is using genetic material to determine gene flow from one population to another.

He examines the size and health

of populations as well.

What fascinates him the most are the differences between the Northern and Southern platypuses.

The platypuses up here in North Queensland are about a third of the size of the ones down South,

which is a pretty big size difference.

It may be because of climate, but it may be because of actual differences

in the species itself.

BLAIR: Populations here are isolated from the populations in the South,

so we're interested in looking at the effects of the gaps in the range,

and especially this far North, and one of the tools that we're using to do that

is population genetics.

NARRATOR: Stephen and his colleague David Blair are working in some of the oldest

rainforest in the world.

KOLOMYJEC: This is Dirran Creek.

It's a tributary of the North Johnstone River Catchment.

It's one of the many Upland freshwater streams in North Queensland,

and it's abundant in platypuses.

NARRATOR: Collecting genetic samples from a platypus can be rather challenging.

Special nets are carefully placed in the streams.

They're not weighted down, so platypuses can swim up to the surface

once they become entangled, to prevent drowning.

With the nets in place, the team awaits until nightfall, when platypuses

are more active.

Then it's time to collect their subjects.

Here's something most people might not be aware of: A platypus should always be held by its tail.

Especially if it's a male.

They're one of the few venomous mammals, with a spur on the hind foot

capable of injecting some rather potent

and painful venom.

So gripping the fatty tail is best for the platypus and the handler.

Now it's time to collect the necessary data.

The platypus is weighed...

KOLOMYJEC: 200.

NARRATOR: And measured, both the body...

KOLOMYJEC: 43.

NARRATOR: And the sizable bill.

KOLOMYJEC: 53.

NARRATOR: The scientists extract samples of DNA.

BLAIR: The principal samples that we're collecting for that is a small piece of skin

from the toe web on the edge of the foot.

That gives us enough DNA, when we take that back to the laboratory,

to be able to do quite a lot of genetic analysis.

In addition to that, we're collecting a little bit of toe skin to go to a laboratory in Adelaide,

where researchers are making cell cultures, for further genetic work.

They're interested in chromosome studies.

They're interested in studies on the rather strange sex chromosomes that platypus have.

Well, most mammals have an XY sex-determining system.

Well, the platypus has gone rather a long way further than that.

The platypus has five X chromosomes and five Y chromosomes.

You can ask the question "Why?"

I can't give you an answer.

NARRATOR: Once the platypus is microchipped...

KOLOMYJEC: There we go.

NARRATOR: It's released back into the water.

KOLOMYJEC: Just let him go gently.

We hope to learn how much difference there is between Northern populations

from Southern populations.

Up here in the North, there are a few gaps where they just do not occur.

And there are no historical records of them ever occurring in those areas.

And so we're looking at what kind of effect these gaps have had on their genetic health.

The actual species -- they might be very different, they might not be different.

It depends on when the last platypus was able to cross these gaps.

NARRATOR: If the smaller Northern platypuses are found to be genetically different

from the Southern platypuses, they may be recognized as a newly identified subspecies,

making them an even more unique version of one of the most unique animals on the planet.

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