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Monday, December 22, 2014         

OCEAN WATCH


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Handfish and frogfish share skill of camouflaging selves

By Susan Scott

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A friend sent me an article recently about Australian researchers naming nine new handfish species, bringing the world's total to 14.

The publication came out a year ago, but it was news to me, and not just because of the new species. I knew that some fish had hands, but I never heard them called handfish.

The best photos I found of these fish are at www.nationalgeographic.com (type "handfish" in the search box and choose the first entry). They look much like the fish-with-hands we commonly see on Hawaii's reefs, except we call them frogfish. Maybe handfish was the Australian name for frogfish?

No, I discovered, the two are in separate families. Still, handfish and frogfish are close relatives, with some remarkable characteristics in common.

One is a fish version of arms and hands. All of these fish have stumpy pectoral fins ending in webbed handlike structures. A joint in the fin bends like an elbow, making the fins resemble arms. Rather than swim, handfish and frogfish walk around the sea floor on their hands.

Both handfish and frogfish belong to a larger group known as anglerfish, a name derived from a flexible spine on the head that hangs over the mouth. On the tip of the spine is a piece of flesh acting as a lure. When a fish or invertebrate comes close to investigate this wiggly bait, the animal rarely lives to regret it.

If a lucky prey manages to swallow the bait and get away, it's no great loss. Anglerfish can grow replacements.

Frogfish (and likely handfish) have the smallest brains relative to body weight of all fish, but they make up for it in speed. In 6 milliseconds a frogfish can open its mouth to 12 times its normal size and swallow prey larger than its own body. This happens so fast that other animals in the neighborhood don't recognize the nearby "rock" as a threat.

Frogfish wear the ultimate cammies, blending in so well with sponges, coral, rubble or seaweed that the fish are nearly invisible.

Even though handfish are related to frogfish, little is known about handfish biology or behavior. Fifty million years ago these fish were common in the world's oceans, but handfish are rare and hard to find today. Besides being only about 4 inches long, they're camouflaged as well.

The 14 species of handfish known today live only in shallow coastal waters off southeastern Australia and range in status from vulnerable to critically endangered to maybe already extinct.

Although we might not be able to spot them often, 11 of the world's 44 frogfish species inhabit Hawaii's reefs. One kind occasionally seen in Hawaii is a hitchhiker. Called the sargassum fish, this frogfish sometimes drifts to our shores on the seaweed it mimics and calls home.

Handfish and frogfish are homebodies, spending most of their lives in one small area. Some frogfish even sit in the same spot for months at a time.

I can confirm this because when I go snorkeling on the North Shore, I like to visit a 6-inch-long frogfish I found last spring in about 4 feet of water. My little fish matches its rock in color and texture so perfectly I would never have noticed it except for one dead giveaway. To brace itself against the rock, the fish extended a hand and planted it on the sand.

Some fish might have hands, but rocks do not.

———

Susan Scott can be reached at www.susanscott.net.






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