The term shellfish is something of a misnomer. Not all “shellfish” have shells, and none of them are in fact fish.
Shellfish is more of a general culinary term that breaks down into three different types: mollusks like clams, oysters and squid, crustaceans like lobsters, crabs and shrimp, and echinoderms like sea urchins.
Here are nine of the more unusual facts about our shelled invertebrate friends that live under the sea.
1. Oysters Can And Will Change Their Sex
All oysters are born male and will swap genders at least once. Given that they are born with both sets of reproductive organs, oysters can also fertilize their eggs.
2. A Sea Urchin’s Mouth Is Called, “Aristotle’s Lantern”
Located on the underside of its body, the sea urchin’s unique, complex mouth has five sharp teeth that can drill a hole into a rock. These chompers can also be venomous, so watch out.
3. Lobsters Are Sometimes Cannibals
While lobsters had been known to cannibalize each other in captivity like some underwater Thunderdome, it’s recently been observed in the wild, too. Typical cases involve adults eating their young, and scientists believe it’s a result of rising sea temperatures from climate change.
4. The Phrase “Happy As A Clam” Is Incomplete
Rarely used, the longer, full version of the saying is “as happy as a clam at high water." The idiom makes more sense in full because a clam at high tide is typically free from predators.
5. Crabs Communicate By The Sound Of Their Claws And Pincers
Crabs create sound by drumming and flapping their sharp appendages in what’s best described as crustacean Morse code. Some species of crab have one exceptionally large claw used for communication.
6. Lobsters Pee Out Of Their Faces, Especially When They Want Blood Or Sex
Lobsters’ antennal glands are the greenish-brown spots near the antennae, and it’s custom for them to pee at each other during battle or courtship. The female, who makes the first move, pees in a male’s shelter several times, creating a pheromonal state of relaxation for the male.
7. One Shrimp Can Lay A Million Eggs
In a single season, a female shrimp will produce an absurd amount of offspring, which hatch around two weeks later. They can also survive in any water conditions as long as there’s food so their breeding area is pretty much anywhere.
8. Clams Are One Of The Longest-Living Animals In The Kingdom.
Scientists have discovered ocean quahogs, a species of clam native to Arctic North American waters that have lived to be over 400 years of age. One specimen collected in 2006, named Ming, was reportedly 507 years old.
9. The Mantis Shrimp Kills Its Prey In The Craziest, Most Brutal Way Imaginable
The mantis shrimp dismembers other shellfish with its two appendages that carry the same velocity as a rifle gunshot—moving so quickly that they boil the water around them, ultimately creating a shockwave that can also kill prey. Not only that, but their shell is so impenetrable that it’s inspired body armor design.