PORTLAND – Ben Alfiero has seen red lobsters, white lobsters and blue lobsters.

As a co-owner of the family-owned Harbor Fish Market, he has come across blue lobsters with white spots, white lobsters with blue spots, and lobsters with extra claws.

But on Monday, he came across something he had never seen before in the decades he has been around seafood: a lobster that was half red and half green right down the middle.

“I thought somebody was pulling my leg,” he said. “I took my fingernail and sort of scratched it. It looks like somebody tipped it sideways and dipped it into boiling-hot water.”

Chris Webber, 15, caught the crazy crustacean Saturday morning near Portland Head Light while pulling traps with his father, Charlie Webber. Charlie Webber, 52, has been catching lobsters for 45 years.

“I’ve been lobstering since I was 7 years old, and I’ve never seen anything like that,” Charlie Webber said.

Chris Webber said he’d like the lobster to end up in an aquarium.

“It’s the most unique thing I think I’ve ever seen in a lobster,” he said. “It’s got to be pretty rare.”

That it is. Bob Steneck, a lobster specialist at the University of Maine’s Darling Marine Center in Walpole, said the mutation is known as bilateral symmetry. Lobsters with the condition look like they’ve been painted one color on one side, and another color on the other side with a line perfectly down the middle.

“I’ve seen bright yellow on one half, I’ve seen blue lobsters that are half blue and half normal color,” Steneck said.

Steneck has worked with lobsters for years and doesn’t get too worked up over something like a weird-colored lobster. But he acknowledges they’re pretty cool.

“They are really fascinating to look at,” he said.