The National Zoo is the new home of 10 giant clams.

Which sort of raises another question: Just how big is a giant clam?

Well, the zoo’s new residents are Tridacna crocea (pronounced TRI-dac-na CRO-say-ah). They are the smallest species of giant clam and can grow to nine inches. The zoo’s clams are about 3 to 4 years old and measure three to six inches.

“This particular species is absolutely beautiful,” said Mike Henley, an animal keeper at the zoo. They have glowing blue, yellow or green blotches, spots or lines. Because they rest in their tanks, they are also great to photograph, Henley said.

In the wild, the clams live in the South Pacific Ocean, where they are accustomed to moving currents and bright sunlight. The zoo re-creates that habitat with water pumps and high-intensity lights.

The clams are in the zoo’s invertebrate exhibit, where you can also see sea stars, spiny lobsters, giant African millipedes, tarantulas and a giant Pacific octopus.