Have you ever seen this guy:
You probably have sometime in your life. If you've ever been to Ocean Beach or Baker Beach, you are very familiar with them. Same thing with fishermen - they know these guys well. What is it? It's a mole crab.
Mole Crabs, sometimes called Sand Fleas, Sand Piggies, Mole Crabs, etc. are little tiny egg shaped crustaceans with three pairs of legs. They are not lobsters, crabs, hermit crabs or shrimp; they are a category on their own: Hippidae. Hippidae crabs are very limited to sandy shores. Although they are found in the intertidal zone, you will almost never see them in rocky tidepools. You will also never find them in muddy calm estuaries. They prefer open sandy beaches that are not protected. That means waves are big and free, and there are no boulders protecting them.
Since mole crabs aren't true crabs, they don't have real pincers. Hippidae and Malacostraca (crabs) both have a hard exoskeleton which is routinely molted.
Have you ever tried to located a sand piggies eyes? Mole Crabs's eyes are long and thin, and actually situated on the back of the body! That means mole Crabs are actually swimming backwards!
There are a few reasons why mole crabs, literally, eyes on the back of their head. One is because while they are half buried in the sand (with their eyes poking out), they can see if a predator is coming. Their rear facing eyes are also good for watching for other mole crabs during mating season.
Mole Crabs have two distinct genders. In the summer and late fall, you might see a female mole crab with orange eggs underneath.
These little "crabs" use two feathery like antenna to filter microscopic plankton from the water. That's why they love waves; with each wave, new bits of plankton are brought in from the deeper parts of the subtidal zone.
If you want to find a mole crab, simply go to tideschart.com to see if the tides are low. Then, go to your nearest sandy beach, and start digging where the sand meets the water. You'll hopefully find these sand piggies in high densities. When you pick one up, stare into it's eyes and say "You are more than a sand piggy!" Be sure to return them after!
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