Coming up, Cameraman Tim makes his debut as a Blue World correspondent as he investigates
one of the oldest animals in the ocean—the Horseshoe crab!
Welcome to Jonathan Bird’s Blue World!
The Horseshoe Crab.
It looks more like a walking helmet than a crab, which isn’t surprising, since it’s
not a crab at all.
It’s more closely related to spiders than to crabs.
This animal has been crawling around on the sea floor for a long time.
In fact, the earliest known Horseshoe crab fossils date back 450 million years!
There are 4 species of Horseshoe crabs around the world, but this one, the Atlantic Horseshoe
crab, is found along the east coast of the USA as far south as the Gulf of Mexico.
The Horseshoe crab lives a quiet life, cruising along sandy and rubbly sea floors, digging
for worms and mollusks like clams and scallops.
If they hang out in shallow water, there is enough light to grow a beard of green algae.
Sometimes they even become a moving substrate for barnacles, mussels and other clingy critters.
Many people think that the long tail called a telson, is some kind of a stinger, but actually
it has a much more practical use.
During the summer when the water warms up, the mating season begins.
Males hang on to the females and follow them everywhere until they are ready to mate.
One of the biggest spawning aggregations of Horseshoe crabs in the world takes place in
the waters around Cape Cod.
Because Cape Cod is basically a huge sand bar, it’s shallow--and sandy--perfect habitat
for Horseshoe crabs.
I’m sending Cameraman Tim on his first assignment as Blue World correspondent to check it out.
Okay, we’re on Nauset beach in Cape Cod, Massachusetts and I’m telling you, we have
the coolest animal in the world.
Tell me what this reminds you of?
This horseshoe crab, it’s ancestors go back almost 450 million years.
What a fascinating little animal.
If you look underneath he’s got ten legs, his mouth and the reason he is called a horseshoe
crab is because his shell, the head shell, looks like a horseshoe.
He’s got two eyes, two compound eyes on the front.
He is not happy that I’m holding him.
He has come up onto the beach because all horseshoe crabs, they are all starting to
breed, and mate on the beach and lay eggs.
Look at him…what does he remind you of?
What movie?
Fascinating.
I’m going to let him go.
There’s a pair coming in right now!
You can see them everywhere.
Those little black shadows all in the shallow water here right now.
And they’re all coming in.
They have one male on the back of a female, and they’re all heading into the shallow
water.
To learn more about the Horseshoe crabs, Tim is meeting up with volunteers from Mass Audubon’s
Wellfleet Bay Wildlife Sanctuary, along with science coordinator Mark Faherty.
So these guys are doing horseshoe crab spawning surveys.
And so this is a standardized method used by organizations, volunteers, state agencies,
federal biologists all up and down the east coast.
And the idea is, these are 5 meter quadrats starting at the high tide line.
And it’s just a standardized way to count spawning horseshoe crabs.
Horseshoe crabs come up to the water line on high tides to spawn.
They spawn in the intertidal zone as well quite a bit on Cape Cod but this is the methodology
that everybody uses so the data is comparable across sites and across years.
Here’s some action right in front of us here.
Look at that one!
That one has a mussel farm growing on it’s back.
She hasn’t obviously been moving quick enough.
They’re holding on for dear life.
Look, one’s got the tail…
This is the end of the spawning season…I don’t think this is the A Team here!
Oh wait a minute!
That one is tagged!
Did you guys read the tag off of this?
Oh yeah, check these guys for tags as you go.
So this is a U.S. Fish and Wildlife tag.
We put it on.
It’s a great activity with school groups.
It’s a great way to involve school groups in the research that we do.
So this is a mark/recapture project where you put a uniquely-numbered tag on the crab
and hope to find it again.
So it gives you information on site fidelity, do they come back to the same spawning site
year after year, how much do they move around, how long are they around, that kind of thing.
And so this is a nice find because we don’t do a ton of tagging at this site.
We do it sort of opportunistically.
So this is a male, and you can tell because they have…their front legs have these sort
of boxing glove-looking things called pedipalps, and that’s for holding on to the female.
The males also have a really concave front of the shell for kind of riding along the
female’s back, and then their mouth is here at the base of the legs.
They have these book gills, these flaps for their gills and they haven’t changed very
much in 480 million years, so I guess it works for them.
They always tell people don’t hold them by the telson.
I’m sure there’s kids out there like me when I was growing up on the beaches in Plymouth
and I thought it was stinger.
“Ooh, the stinger watch out!” but it’s totally harmless.
Don’t pick them up by the tail.
It’s to help them (because it can break off sometimes) it’s critical for helping
them flip themselves over if they end up on their back.
They have all kinds of eyes.
They have more than just these two.
They have light receptors even on the telson and other places.
There’s one right there.
Look at this!
Look at that!
They’ve all got tags!
Let me know when you’re ready.
That does look newer.
353399.
This is what we came for right here!
This is happening right now!
Check it out!
You can see this great big lump in the water in the front is the female.
She has dug into the sand and she is laying the eggs right now.
The male, who is attached to her back, he is waiting for the eggs to go into the sand,
and he can fertilize them.
She’ll get up and she will move along and she’ll dig back down and I mean, this is
what we came out here for, to see this.
And this is what surveyors and Mass Audubon is looking for is this little action right
here.
That’s what it’s all about.
Horseshoe crabs are something I have seen on my dives here in New England ever since
I first started diving.
They’re animals that many people take for granted.
But I learned a lot about the Horseshoe crab from Cameraman Tim’s investigation.
And as long as they continue to spawn here in the waters of Massachusetts, hopefully
this enigmatic species will be around for another 450 million years in the Blue World.
If you are a fan of the Horseshoe crab and you would like to volunteer for a Cape Cod
survey, contact the Mass Audubon Society at the link in the description.
And don’t forget to subscribe!
And check out our “merch” link in the description for some Blue World swag!