What makes a blue lobster so blue?

A catch of colourful crustaceans is stirring the pot at a fish market in Nova Scotia, but the brilliant lobsters are more than just a novelty — blue and orange lobster are telling scientists about the ocean's ecosystem.

In June a fishermen caught a bright blue lobster in the waters of Antigonish – the odds of that were pegged at one in two million. Finding 35 orange lobsters is even less likely. Catching one is supposed to be a one-in-ten-million rarity

The colouration is caused by a genetic defect that causes the lobster to produce an excessive amount of a particular protein that gives the lobster the unique colour.

"They look exactly the same except they look totally different," said Andrew Hebda, curator of zoology at the Museum of Natural History.

"When you think about lobster think of a painting. You're doing some water colours and you take a bit of blue, you take a bit of yellow, you take a bit of red and you take a bit of green and poof, mix them all together and what do you have? Mud. Which is what your normal lobster is. What happened here is that we don't seem to have those other three pigments in there… you're looking at a genetic mutation that has suppressed those colours."

Live lobsters are usually a motely mix of greenish browns. They turn red when boiled.

"That's essentially good camouflage colour. If you're living on a fairly rocky bottom you don't want to stand out. If you've got predators around going 'whoa, there's food wandering around."

Escaping predators

Hebda said the museum's last record of an orange lobster was in the 1920s.

"I suspect we're not seeing a higher frequency, it's just that they are not being picked up so they are persisting," he said.

Hebda said their prevalence might indicate there are less predators.

"They are food to a large number of predators so again if the things that feed on them aren't there then they'll persist."

Hebda said there are similar reports of colourful lobster in New England.

He said their unique colours probably doesn't affect their meat.

"It's shell deep. You can't tell a taste of a lobster by its appearance, unless it happens to be laying on the bottom of the tank for several days not moving."

No one will find out what the orange gang tastes like. Some might be donated for research, while the rest will spend their days in the pet tank at the store.