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{♫Intro♫}
Look at pictures of whales -- especially right whales --
and you might notice characteristic white patches on their heads and faces.
You might think these are just weird skin growths. Which, they are, but there’s more
to them. Those white patches are only white because they’re crawling with crustaceans.
And believe it or not,
these weird little dudes can tell us a lot about the whales they rode in on.
Those white spots are called callosities because, well, they’re basically calluses.
These are places where dead skin gradually builds up -- instead of
drying and shedding away like it does on the rest of the animal.
Weirdly, callosities form on the heads of right whales in the same
places we humans have facial hair: above their eyes, along their lips and jaws,
and even between their blowholes and the tip of their snout. Like the whale version of a mustache!
Baby whales are born without any callosities, but they start to develop within a few months.
We don’t really know what they’re for, any more than we know what mustaches
are for. But just like a mustache, these patterns are very distinctive.
The exact pattern is unique to each whale, almost like a fingerprint, which is super useful because
it helps scientists identify individual whales and keep track of how their populations are doing.
But here’s the thing: whale callosities are naturally gray. They only look white because…
well, they’re covered in lice.
Because even the ocean isn’t safe from lice. Sort of, anyway. We call them whale lice,
but they’re not true lice — they’re a kind of crustacean called a cyamid.
The head of a single right whale can have tens of thousands of cyamids living on it.
They find their way to young whales within a couple weeks after birth,
settle in, and start munching away on their dead skin.
They can’t swim, so scientists think they’re transferred by
close contact between whales -- like from mother to calf during nursing.
Once they’re in place, their flat bodies and sharp,
grasping claws help keep them from washing away.
Scientists are still trying to figure out whether whale lice are just along
for the ride, or if the whale actually benefits from having them on board.
One possibility is that they actually help their host whale locate food.
Callosities are often scattered with stiff hairs that might help whales
sense the movements of prey in the water around them -- kind of like whiskers.
And it’s been suggested that the lice might enhance that ability.
See, we know that crustaceans closely related to whale lice
stand up when they sense tiny prey animals passing by -- in order to catch and eat them.
So it’s possible that the whale lice that hang out on the whales’ sensory hairs
are moving around in a way that helps the whale tell where food is.
Scientists aren’t yet sure if that’s the case, though. But even if it’s not true,
whale lice don’t seem to cause much of a problem for their hosts.
And strangely enough, they provide a benefit for us humans -- the ones who study whales, that is.
Different whale species often carry different whale lice species.
In fact, right whales alone are home to multiple kinds of cyamid.
The two that live on healthy right whales each have their own little microhabitat.
One lives in deep pits in callosities, while the other one hangs out in more open spots.
There’s also a species that’s orange instead of white and usually only
infests whales that are very young or sick. Which means looking out for these
orange cyamids is one way scientists can tell how healthy a right whale is!
That’s not all they’re good for, either. Because they’re literally stuck to their hosts,
whale lice can tell researchers a lot about what goes on when they’re not looking.
For example, looking at genetic differences between the lice that hang out on the three
species of right whale has helped scientists figure out a lot about those species’ history.
Cyamid populations closely track the size and structure of the populations of their host
whales -- but because each individual whale can host thousands and thousands of cyamids,
there are way more individual cyamids than there are whales.
This means there can be a lot more genetic variation among whales’ cyamids than among
the whales themselves. And that means more information for scientists to pore over.
From tracking the genetic variation of their lice, we’ve inferred that the
three species of right whale split from each other around six million years ago.
The two species in the northern hemisphere are now endangered, thanks to whaling. But
lice genetics also show that they were once as abundant as their southern hemisphere cousins.
And in one of the most unusual cases of all, researchers once found a beached
right whale calf that was covered in a species of cyamid normally found on humpback whales.
That suggested the right whale had been cared for by humpback
whales -- it was raised by a different species.
So not only are those white patches on whales alive,
they’re also really useful to biologists who study whales and work on their conservation.
It turns out that these “lice” aren’t just gross creepy crawlies -- they have stories to tell.
The more we understand
about the world, the more we can unravel stories like these. And the courses at Brilliant can help.
Like their course on Statistics Fundamentals,
which is all about the math we use to help decide what’s real.
Brilliant has loads of other courses too, in math, science, engineering, and computer
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so thank you. {♫Outro♫}