Chameleons and octopuses are known for their rapid color changes, but fish? It turns out that at least one species of fish—the rockpool goby—is a quick-change artist, too.
There have been anecdotal reports of gobies and other tidepool fish that are capable of changing colors, but scientists have largely ignored the behavior until recently. A study published October 15 in the journal PLOS One is the first to measure this ability in a fish, the rockpool goby (Gobius paganellus). The new research shows that using color change for camouflage might be more common in the animal kingdom than previously thought. (See “Photos: Master of Disguise—Amazing Insect Camouflage.”)
The goby’s tidepool habitat is a challenging environment for a little fish. There is a wide range of different backgrounds, and tides and waves can push the animals over them fairly quickly. For fish that wish to stay hidden from predators that treat the intertidal zone like their own personal buffet, such as birds and larger fish, that can be a problem.
Researchers from the University of Exeter in the U.K., led by Martin Stevens, thought the gobies might benefit from being able to rapidly change color to camouflage themselves in such an environment. They discovered that the rockpool goby can change its color and brightness to blend into different backgrounds. And what’s more, the animals can accomplish the change in less than a minute.
Stevens and his colleagues collected rockpool gobies from tidepools in Cornwall, U.K., and placed the fish in seawater-filled trays with backgrounds of different brightness (black or white) and color (red or blue) and recorded what happened.
The researchers found the gobies tried to match their background by becoming brighter on white backgrounds, darker on black backgrounds, more red against red backgrounds, and a darker gray on blue backgrounds.
“The speed of the change came as something of a surprise,” says Tom Sherratt, a biologist at Carleton University in Ontario, Canada, who was not involved in the research. “But I guess any fish that took its time to blend in with its background would rapidly become lunch,” he adds. “The findings make one wonder why more species cannot color change in the way gobies do!”
A Fish of a Different Color
“I initially thought the gobies would show the most dramatic changes for brightness because they’re not especially colorful animals until you see them up close,” Stevens says. “But our study suggests that color may actually be more important because we found the level of color change was stronger than that of brightness.”
The gobies’ camouflage abilities also suggest that some types of color are easier to take on than others. Although the fish turned red against a red background, they couldn’t quite match a blue background. Blue is rare in their home environment, Stevens says, but there are many red objects, such as red algae and red-brown stones and seaweed. So it’s probably more important for these gobies to be able to turn red than blue.
While gobies don’t change color quite as quickly as chameleons or octopuses, Stevens says the fish’s color change abilities are quite nuanced. “They’re able to change brightness independently from color and vice versa,” he says. (See “Beautiful Octopus Pictures: Masters of Disguise and Agile Hunters.”)
Devi Stuart-Fox, a zoologist at the University of Melbourne in Australia, who was not involved in the study, was impressed by Stevens’s use of state-of-the-art methods in image analysis to measure the gobies’ color change. “[And] they didn’t stop there,” she says. The authors then went on to estimate whether bird predators would be able to spot the color-changing gobies. They found that the birds couldn’t, “and that’s what counts to a goby,” Stuart-Fox explains.
Stevens plans to delve deeper into these camouflage artists. He’d like to find out whether gobies can tune their camouflage to the visual systems of different predator groups, such as fish and birds, in the same way that chameleons do. For instance, do gobies change their camouflage at low tide to hide from birds, but choose a different camouflage for high tide to escape the notice of other, predatory fish? Only more research will tell.