Once a Spawn a Time: Horseshoe Crabs Mob the Beach | Deep Look

Horseshoe crabs may look scary, but when it's springtime in Delaware Bay, millions of these arthropods show they're lovers, not fighters. They lay masses of blue-green eggs up on the shore. At just the right time, they pop and release the larvae within the sea.

WATCH our crab collab episode with OVERVIEW on@pbsterra!    • Why Are There 30 MILLION Horseshoe Cr...  

DEEP LOOK is an ultra-HD (4K) short video series created by KQED San Francisco and presented by PBS Digital Studios. See the unseen at the very edge of our visible world. Explore big scientific mysteries by going incredibly small.

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Each spring during May and June, Atlantic horseshoe crabs gather by the millions along the East Coast of North America with only one thing on their mind — a springtime spawning spree!

From Maine to the Gulf of Mexico they seek out calm bays and estuaries, waiting for the highest tides to emerge from the waves. They dig down into the wet sand and deposit huge numbers of pea-sized eggs.

David R. Smith, a biological statistician who studies horseshoe crabs for the U.S.Geological Survey, has come to Slaughter Beach, Delaware, to witness the spectacle under the glow of a full moon.

“It's sort of like looking back in time,” says Smith, “That same scene of these marine creatures coming to the water's edge on a quiet sandy beach to spawn has been repeated for millions and millions of years without much variation.”

--- What do horseshoe crabs eat?
Horseshoe crabs mostly eat worms and mollusks from the seafloor. But they aren’t picky, they’ll eat other things like small fish and different crustaceans.

--- Why do horseshoe crabs lay their eggs on land?
By laying their eggs in the damp sand, they protect their eggs from the many predators that live in the sea. It allows their offspring a chance to develop before another high tide carries them into the sea.

--- Why do horseshoe crabs have blue blood?
Like other mollusks, horseshoe crabs have blood that carries oxygen using a copper-containing protein called hemocyanin. The hemocyanin turns blue when exposed to oxygen. Vertebrates like humans have iron-containing hemoglobin in their blood, causing it to turn red when exposed to oxygen.

---+ Find additional resources and a transcript on KQED Science:
https://www.kqed.org/science/1976488/...


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---+ Shoutout!

🏆Congratulations🏆 to the following 5 fans on our Deep Look Community Tab for correctly answering that the body part a male horseshoe crabs use to grab onto their mates is a clasper, a modified pedipalp!

Sinister Omen
SARA FATIMA
Anirudh Anilkumar
Uwis Qurni Abdullah
hudson urruttia

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