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Don’t Drag Me Through the Mud: The Unusual Oyster Toadfish - August 6, 2017

As a general rule here on the Eastern Shore, blobs of mud tend to stay put. They do not tend to, say, wiggle and jiggle around the bottom of a boat, and they certainly don’t tend to bite, snap, croak, or otherwise make a fool of themselves. Under no circumstances should a blob of mud move on its own at all, much less make a noticeable commotion. Now imagine my surprise when, on a trip pulling abandoned crab pots earlier this year, I met a particular blob of mud who held no such reservations.

Many of you may have caught a glimpse of this peculiar creature at the bottom of your muddiest, filthiest crab pots. If you were to become curious, as I was, and take a closer look at this rambunctious blob of mud, you would find one of the ugliest faces in the ocean peering back at you with a jowly scowl that puts Winston Churchill to shame. Wash the filth off your new friend and you will find that his appearance hasn’t much changed; he’s still just as bulbous, warty, and hideous as he was before, although perhaps a bit more symmetrical. This grotesque little fellow is the oyster toadfish (Opsanus tau), also called the oyster cracker and (my personal favorite) the ugly toad. Named for their warty, toady countenance, these foot-long, tadpole-shaped fish are part of family Batrachoididae, each member of which is uglier than the last.

The oyster toadfish has a personality to match its appearance, and will often bite an unsuspecting angler with powerful jaws and rounded teeth. Since toadfish are ambush predators, they need a hard, fast bite: they use their unsightly camouflage to stay unseen until the last possible second, then lash out at incautious prey. The bite of the oyster toadfish is fast enough to catch squid and small fish, and strong enough to break the shells of prey items like crabs, clams, and oysters. On the receiving end, it feels like being hit in the finger with a hammer. To make matters worse, toadfish are equipped with sharp defensive spines on their dorsal fins, used to protect themselves from predators like sharks and rays. Ugly, cranky, and always ready for a fight, the oyster toadfish is also known to some anglers as the “Mother-in-Law” fish. 

 However, there’s more to these unusual fish than just a revolting face. From April-October, the male toadfish does what many angsty teens do to try and attract a mate: he turns to music. The lusty lad builds a nest out of sand and rubble, then croons to his mate with sensual foghorn sounds made by vibrating his swim bladder. If the female likes his song enough, she will attach her unusually large eggs to the nest, where the male then fertilizes them. The poor oyster toadfish has a face that not even a mother could love; the female leaves the nest almost immediately after laying her eggs. And yet, the eggs still receive a remarkable amount of parental care from the male fish. The father stays for the entire developmental period, protecting his brood from predators, cleaning out debris from the nest, and fanning the eggs with his fins. The eggs hatch after about a month, and papa fish continues to protect them for a few more weeks, even after they can swim on their own.

No matter how ugly the oyster toadfish is, it’s really what’s on the inside that counts. Scientists working on muscle spasm disorders are fascinated by the insides of the toadfish; specifically, the muscles it uses to create its foghorn serenade. Producing sound by vibrating your swim bladder is an incredibly inefficient form of making noise so, in a bout of evolutionary stubbornness, toadfish have developed incredibly fast muscles to sustain the sound. As a result, the sonic muscles of the oyster toadfish are the fastest moving muscles of any vertebrate. This incredible capacity for muscle contraction makes it an excellent study organism for muscle weakening diseases like nemaline myopathy, and could help researchers understand how to make human muscles work faster and longer.

The oyster toadfish is also a wonderful model organism for vestibular research, which is the study of the inner ear and how it relates to hearing, balance, and body movement. Not only is the architecture of the fish’s ear very similar to our own, the big fat head of the oyster toadfish provides enough space to more easily understand such minute structures. Their spacious craniums even bought the oyster toadfish a trip to space: In 1998 four oyster toadfish broke the bonds of Earth and orbited over 6 million miles on NASA’s STS-90 space shuttle mission. Later that year two more toadfish were shot into the stars alongside John Glenn on the ST-95 mission. Both experiments helped NASA scientists better understand how spaceflight affects balance, equilibrium, and motion sickness. 

While they may be hideous, aggressive fish, they have a soft spot for their kids and a padded scientific resume to boot. From the bottom of your crab pot to the final frontier, these unique and unsightly single dads have made their mark on human medicine and space travel.

Not too bad, for a rowdy blob of mud.

Simons is a seasonal scientist with the Maryland Coastal Bays Program.



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