[Jim Morin] As soon as we got in the water, the reef erupted in this just glorious display
of light spots.
[Trevor Rivers] It's, for me, the closest thing to magic that I've ever seen.
[Narrator] On moonless nights in the Caribbean, the sea erupts in spectacular displays put
on by tiny crustaceans called ostracods.
In other parts of the world these creatures only produce light to scare off predators.
But in the Caribbean, male ostracods spew glowing mucus to attract females.
[Jim Morin] When I started the work, there were two known species that emitted light
in the Caribbean.
And now we have well over 100.
That's just the tip of the iceberg.
We can't keep up with descriptions because we're discovering so many so fast.
[Gretchen Gerrish] On the reefs, we often find six or eight different species.
Some species will be way down in the sandy channels there.
One of my favorites is Maristella chicoi, which does these radiating displays.
Then on the margin of the coral is this downward displaying species that just is on the slopes
of the coral in patch reefs.
Then over that very, like top of the reef, you'll get these slow upward displays, and
this other one we call a rocket.
[Trevor Rivers] You look at a firefly, where the flash is the fireflies still is.
In ostracods, the luminescence is in the past.
You might see three or four or five or more pulses – that's still not where the male
is.
You might see three or four or five or more pulses – that's still not where the male
is.
Individual pulses could last for upwards of 10 seconds.
So you've got 100 milliseconds on one side or less, and then you've got 10 seconds on
the other side.
[Narrator] As researchers continue to discover new species, advances in camera technology
since the early 2000s have allowed them to better study these courtship displays.
[Trevor Rivers] The recording capabilities that we had were a generation two night vision
device.
But it's just green, right?
There's no actual true color coming through.
[Jim Morin] To determine quantitatively what's going on, we would then project those tapes
onto a screen and then we would laboriously map out each display.
How long each pulse lasted, how far they were apart and so on.
These days, there are low light level cameras all over the place.
Most of our workers now have these cameras, and they're able to get the videos and these
displays very easily with no fuss no muss.
[Trevor Rivers] The way things have changed since I started in 2001, to now has pretty
much made it that I could probably have done my dissertation in a matter of months, rather
than five years.
We got to work with Martin Dohrn.
He created what's called the beam splitter where we could actually record with infrared
on one and then right in the same field of view, it would split and we can look at the
luminescence with a infrared filter on top of it.
[Narrator] Being able to see ostracods and their bioluminescent signaling at the same
time helps scientists determine just how many males are present during courtship displays.
[Trevor Rivers] There's an incredible amount of competition and interactions going on in
complete darkness, that we don't even see until we got the infrared going in the field.
[Gretchen Gerrish] Sometimes you can get upwards of 30 to 40 males swarming the displaying
male.
Those males are trying to capture the female before she can reach the one that's displaying,
so we call them sneakers.
[Narrator] In addition to recording signaling, researchers also capture ostracods to study
their anatomy and genetics.
This helps them classify species and understand their evolutionary history.
I got really perplexed in Puerto Rico.
We recorded different display types.
We saw them in different habitats.
And every time we collected them, they looked exactly the same.
What we found is in Puerto Rico, there was this clade of one genera that had radiated
into all these habitats and in all these unique groups, versus in other places, we find like
all three or four of the genera that we often find.
[Jim Morin] There's this range that allows you so much latitude in terms of looking at
both ecological diversification, as well as evolutionary diversification.
[Narrator] Major questions remain, like why only ostracod species in the Caribbean use
bioluminescence for signaling, and how so many species evolved to occupy different parts
of the environment.
[Trevor Rivers] I want the world to know about them,
and hopefully that will help with conservation and an appreciation for the environments that
we’re at.