Two-toned lobsters, they explain, are rare but not unheard of.
The shells of American, or Maine, lobsters usually sport a combination of yellow, red, and blue pigments. But the animals grow symmetrically, with each half of the body developing independently of the other.
In the case of Robinson's catch, half of the lobster's shell was lacking the blue pigment, giving it the appearance of having been cooked to a turn.
All this makes Robinson's fifty-fifty find one for the record books, the Oceanarium's staffers say.
The aquarium has received only three two-toned lobsters in 35 years, they note, and the odds of finding one that's exactly half and half is about 1 in 50 million.