Horseshoe Crab Facts ~ Horseshoe Crab FAQ & Pictures

by Bob

in Sea Life

Horseshoe crabs are bottom-dwelling creatures that are often called living fossils because they predate the dinosaurs by some 200 million years. They are not crabs at all and are more closely related to spiders and scorpions. With their unique horseshoe-shaped shell, they are not hard to notice.

Horseshoe Crab

Horseshoe Crab

Here are some neat horseshoe crab facts & FAQ:

Is the horseshoe crab a true crab?
No. True crabs have two pairs of antennae and a pair of jaws which horseshoe crabs lack. True crabs have 5 pair of legs while the horseshoe crab has seven.

How many species of horseshoe crabs are there?

  • Mangrove horseshoe crab, found in Southeast Asia
  • Atlantic horseshoe crab, found along the American Atlantic coast and in the Gulf of Mexico
  • Tachypleus gigas, found in Southeast and East Asia
  • Tachypleus tridentatus, found in Southeast and East Asia

What do horseshoe crabs eat?
Small clams, sea worms and even algae. Since they have no teeth, they must crush their food with their legs.

What is the average size of a horseshoe crab?
20 inches and weighing 33-4 pounds. They can reach 24 inches and weigh up to 6 pounds.

How many eyes does a horseshoe crab have?
10. Evenly distributed around the body including on top of the shell. 2 compound eyes reside on each side of their shell which are used to locate mates during spawning season.

How do horseshoe crab reproduce?
They reach reproductive maturity at 8-11 years of age. Around May of each year, males make their way to the edge of beaches searching for females. A couple of weeks later, the larger females show up and release a pheromone that stimulates the male. Male(s) then attach themselves to females and commence fertilization. The female then digs a hole in the sand and releases several thousand eggs. 14 days later, baby horseshoes are born.

Horseshoe Crabs Mating - Horseshoe Crab Facts

Horseshoe Crabs Mating


How small are baby horseshoe crabs?
Very small:

Horseshoe Crab Baby

Horseshoe Crab Baby

How do horseshoe crabs swim?
They swim upside down.

Where are horseshoe crabs found?
The Atlantic horseshoe crab is found all along the East Coast of the U.S. from Maine to Mexico. A few strays do manage to make it to Europe. The other 3 species are found in Southeast Asia.

What is the heart rate of a horseshoe crab?
32 beats per minute.

How long do horseshoe crabs live for?
Their lifespan ranges up to 20 years.

What are some predators of the horseshoe crab?
Many migratory birds as well as sea turtles and fish eat their eggs. Adults have little edible flesh and along with their hard shell makes them unappealing as prey to almost all animals, although loggerhead sea turtles do eat adult horseshoes.  This is why they have survived for 400 million years.

Is the horseshoe crab a crustacean?

Is a horseshoe crab edible?
There are no meaty parts to eat. There really is nothing to a horseshoe crab except its outer body parts and organs.  The only edible part would be the eggs.

Is the horseshoe crab poisonous?

Is the horseshoe crab venomous?

Is the horseshoe crab dangerous?
Not at all. It’s menacing tail is actually used as a rudder and to right itself if it flips over.

Is the horseshoe crab a dinosaur?
They predate the dinosaurs by 200 million years.

Is the horseshoe crab a carnivore?
It’s considered an omnivore as it’ll eat most anything it finds as it burrows on top of the muddy ocean bottoms.

What is the scientific name for horseshoe crab?

What about horseshoe crab eyes?
They have 10 of them.

Is there horseshoe crab farming?
Yes, for their blood.

What about horseshoe crab blood?
It’s blue and is very sensitive to bacterial toxins. Horseshoe crab blood, at $60,000/gallon, is valued to such an extreme degree because it is not only employed worldwide in bacterial contamination tests, it is also used in testings for every single drug approved by the FDA, making it a $50 million/year industry. Read more here.

Can horseshoe crabs be kept in an aquarium?
Yes. 200 gallon tank minimum.

Can horseshoe crabs be kept as pets?
Yes, but they are fairly difficult to keep alive.

Are horseshoe crabs endangered?
The Atlantic horseshoe crab is considered near vulnerable.

What is the horseshoe crab population?
The Atlantic horseshoe crab population is estimated at 2-4 million.

Why do horseshoe crabs wash up on shore?
Horseshoe crabs grow by molting. They increase in size by 25% after each molt and what you’re seeing on the shore are their old skeletons.

Why are horseshoe crabs considered living fossils?
They have been around for 400 million years which is 200 million years earlier than the dinosaurs.

Are horseshoe crabs related to trilobites?
Yes. They are closely related to these long extinct creatures.



Are horseshoe crabs related to spiders?
They are in the same Subphylum (Chelicerata).

What about horseshoe crab tail?
Although it appears menacing, it is really just used as a rudder and to flip an overturned crab.

What is the average price for horseshoe crab blood?

Know any additional horseshoe crab facts?  Leave them in the comments below for others to read.

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