December 2, 2013
A Fish Out Of Water Relies On Camouflage To Escape Predation
[ Watch the Video: Land-Dwelling Fish ]
Brett Smith for redOrbit.com - Your Universe Online
A leaping, legless, land-loving fish called the Pacific leaping blenny isn’t just one of the odder creatures found on Earth – it’s also emblematic of life’s transition from life in water to life on land.
A new study published in the journal Animal Behaviour has found these strange fish-out-of-water depend on camouflage to escape would-be predators.
"This terrestrial fish spends all of its adult life living on the rocks in the splash zone, hopping around defending its territory, feeding and courting mates. They offer a unique opportunity to discover in a living animal how the transition from water to the land has taken place," said study author Terry Ord, an evolutionary biologist at the University of New South Wales.
The bizarre fish measures between 1.6 and 3.2 inches long when fully grown and leaps using a tail-twisting technique. It lives on land its entire adult life, but has to stay moist in order to breathe through its gills and skin.
To determine the potential effects of camouflage, the study team began by measuring the color of five different populations of the blenny found around the Pacific island of Guam. The colors of the fish were compared to the color of the rocks they lived on.
“They were virtually identical in each case,” Ord said. “The fish's body color is camouflaged to match the rocks, presumably so they aren't obvious to predators.”
Next, the researchers created realistic but fake blennies out of plasticine.
"We put lots of these model blennies on the rocks where the fish live, as well as on an adjacent beach where their body color against the sand made them much more conspicuous to predators," Ord explained. "After several days we collected the models and recorded how often birds, lizards and crabs had attacked them from the marks in the plasticine.”
“We found the models on the sand were attacked far more frequently than those on the rocks,” he added. "This means the fish are uniquely camouflaged to their rocky environments and this helps them avoid being eaten by land predators."
The study team also looked at the body colors of closely related species that either lived in the water or were amphibious like the leaping blenny.
"These species provide an evolutionary snapshot of each stage of the land invasion by fish," Ord said.
The team noted remarkable similarities in color among these species and suggested the ancestors of the Pacific leaping blenny already had a coloration that matched the shoreline before they began spending more of their time out of the water.
Ord and his colleague S. Tonia Hsieh of Temple University have been studying the foraging and mating habits of the Pacific leaping blenny for years. In a 2011 interview with National Geographic, Ord noted these animals are still fish – even though they spend much of their time on land.
"While these fish are very good at living on land ... they are nevertheless very constrained by their evolutionary history," he said.