Scientists Fishing for Clues

Four-thirty a.m. came awfully early this past fall as I prepared for a daylong fishing trip near Point Lookout at the southernmost tip of Maryland's western shore. By 6:30 the rain had let up to a thin drizzle, and I had a feeling fishing would be good today. Now I'm not much of an angler; actually I just barely qualify as a novice. But anyone willing to get up this early, in the rain, with no guarantee of fish must have a thread of angler running through her.

Once the captain found his spot, we baited our hooks and the game began. "Fish on" was the phrase I heard all around me that morning as lines whirred and blues were hooked. I really wanted to catch a big bluefish or maybe a rockfish. I actually had two chances but, as luck (and my inexperience) would have it, I lost both to broken lines. Finally, I called "fish on" and this time I brought it aboard. But instead of a glistening bluefish fighting on the deck, my catch, Opsanus tau, landed with a thud. It was a toadfish.

Now if you've never seen a toadfish, I can only say they are aptly named. A round, flat head and large gaping mouth gives it a monstrous pollywog look. Scaleless, slimy skin and bulging eyes complete the homely appearance. The toadfish is an ambush eater. It lies on the bottom and waits for prey, aggressively snapping at anything that comes by. It has strong jaws and stubby teeth to crush mollusks, crustaceans and just about anything else.

Everyone consoled me on my catch as the mate noted that, although they have no commercial value, toadfish are edible. To prove his point he cut out some meat, cooked it with some crab spice and passed it around to all who would dare. It was pretty tasteless and reminded me of the school lunch fish sticks I ate in third grade.

The fishing was good for the rest of the day. Fillets of blues and even a few rockfish were distributed that evening, but I never caught my prized fish. A few days later though, I did a little digging on the lowly toadfish and was surprised at what I found.

The bladder of the toadfish is the fastest twitching muscle in the vertebrate world. A toadfish can vibrate its swim bladder 200 times per second. That's twice the speed of a rattlesnake's tail (90 vibrations per second) and at least four times as fast as a hummingbird's wingbeat (50-60 times per second). The toadfish doesn't use this muscle to help it move or catch prey. Toadfish vibrate their bladders to create a grunting noise, similar to a toad croak or foghorn.

When ready to spawn, the male toadfish searches for and secures a nest, a semi-enclosed area of debris on the Bay bottom. He then uses his bladder to send out a low plaintive call to attract a female to him. Spawning takes place from April to October. An attracted female will deposit eggs on the nest and swim away. The male fertilizes the eggs and then protects and nurtures offspring for weeks.

Scientists are interested in looking at toadfish in relation to heart disease and nerve regeneration. Since they are able to contract and relax their bladder so fast, toadfish might be able to provide information to help understand why some human heart muscles fail. In terms of nerve regeneration, scientists have learned that, unlike a human spinal cord which when cut does not grow back, the toadfish's will. Studies using toadfish may also help with advances in devices for patients with central nerve damage.

Toadfish can also survive in ammonia concentrations that would kill almost every kind of creature. High ammonia is associated with many diseases, including liver problems. When a liver is damaged, it is unable to filter and excrete ammonia, a waste product. The tissue most sensitive to ammonia is the brain.

If scientists can discover the mechanisms toadfish use to tolerate ammonia, they may also be able to figure out ways to make humans more tolerant of higher ammonia levels associated with the onset of certain diseases or halt ammonia's toxic effect on people.

And last but not least, the toadfish has been in space. A space shuttle mission in 1998 took along a few toadfish to study the effects of microgravity on our balance or vestibular system. Balance is so critical to all animals that it's the first one of the sensory systems to evolve. Because their vestibular system is so similar to humans, the toadfish is a model for learning about balance disorders like motion sickness.

Anglers probably don't care much for toadfish. Most of us probably can't even appreciate their importance to the ecology of the entire Chesapeake Bay system. But toadfish are important. Like so many other inconspicuous plants and animals, toadfish may possess hidden benefits, providing clues that someday may improve our health and add to the quality of our lives.

Kathy Reshetiloff is employed by the U.S. Fish and Wildlife Service, U.S. Department of the Interior. Photo by Rich Mason, U.S. Fish and Wildlife Service. Photos courtesy of the Virginia Institute of Marine Science.


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