Upside Way Down: Video turns fish story on its head

Oceanographers watching the live video nicknamed the animals “Zappa fish” because of what seemed to be a long, beardlike barb coming off their chin. Jason, a remotely operated vehicle servicing ocean-bottom instruments at the Hawaii-2 Observatory in the Pacific Ocean, was capturing the pictures as the bizarre fish hovered just above the seafloor at a depth of about 5,000 meters.

The images, which researchers from the Woods Hole (Mass.) Oceanographic Institution posted on the Internet 3 years ago but couldn’t identify, stand as the first video recordings of any deep-sea anglerfish. What’s more, the pictures overturn long-held notions of how some anglerfish behave. “I was astounded to see the fish swimming upside down,” says deep-sea biologist Jon A. Moore of the Florida Atlantic University in Jupiter. The barb actually extends from its nose.

Soon after Moore saw the 4 minutes of video footage of three fish, he identified them as rare whipnose anglerfish. He reports the first description of these fish doing the backstroke in the December Copeia. The finding challenges textbooks that have long depicted this and 20 other known Gigantactis species as swimming upright with their fishing-rod–like illicium protruding off the top of their heads. The illicium is a modified dorsal fin harboring bioluminescent bacteria that make it glow.

“It’s really one of the most spectacular discoveries, at least with these animals,” says Theodore W. Pietsch, an ichthyologist at the University of Washington in Seattle.

Finding the fish at the very bottom of the ocean, instead of higher in the water column, was a big surprise, he says. And instead of dangling its glowing lure to attract prey, the fish appears to use its rod to troll for critters on the seafloor.

Video clips can be viewed at http://www.whoi.edu/science/AOPE/cofdl/stace/H2O/H2O_fish.html.

Before the video became available, biologists could only speculate about this obscure fish’s behavior by studying the occasional dying or dead specimen caught in a deepwater trawl.

Pietsch thinks the whipnose’s odd foraging behavior may explain why its elongated body and big tail differ from those of other, more globular anglerfish, which researchers believe lie in wait for prey attracted to the fish’s lure. The whipnose’s features probably help it actively search for prey in a resource-limited environment, says Pietsch. “There is so little to eat down there, to let something go by would be a big mistake,” he says.

He and Moore both note that male whipnose anglerfish lack illiciums, so the videotaped fish are females. Also, females grow up to 1 meter long, which dwarfs males. To mate in their otherwise desperately lonely habitat, the 10-centimeter-long males seek out and bind to the females using their jaws. The deep-sea couple’s tissues and bloodstreams sometimes fuse permanently, the male feeding off the female. Some pairs eventually split up, but others are stuck in this parasitic marriage for life.

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