One or another aspect of Opsanus anatomy makes it a good model for research into:

insulin secretion, 
diabetes, 
hearing,
dizziness, 
nausea,
motion sicknesss, 
drug metabolism, pollution, and toxicology

 To begin with, you might wonder what a vestibular system is. "Most of it is reflexive in nature, so we're not aware of it until it malfunctions," Highstein says of the system that provides our sense of balance and equilibrium. When your vestibular system isn't working-- when, for instance, you are suffering from motion sickness-- any number of other systems are thrown out of kilter.

 "You're lying on your bed," Highstein says. "You're dizzy. Your vision is moving. Your digestion is affected. You certainly have trouble doing any deep thinking. . ."

 In fact, virtually all other systems receive input from the vestibular system, which consists of fluid-filled canals in the ears of vertebrates. The linings of the canals are covered with hair cells that sense the movement of calcium carbonate crystals known as otoliths. Changes in the position of the head cause the otoliths to move, and the hair cells sense the movement and pass that information along to the brain.

 Information about balance, movement, and location is so critical to animals that the vestibular system was one of the first sensory systems to evolve, says Highstein, an M.D./Ph.D. professor at Washington University School of Medicine. Not only were the vestibular organs an early invention, but the system of canals and hair cells and otoliths has not changed much over the eons.

 "Evolution got it right the first time, when the vestibular labyrinth first appeared more than 300 million years ago," Highstein says. The vestibular organs in fish are very similar to ours, says Highstein, who studies balance from soup to nuts, including the biophysics and biochemistry of the vestibular organs, the transduction of signals to nerve impulses, and the processing of visual information by the brain. An understanding of the vestibular system may eventually point the way to therapies for hearing impairments, motion sickness (including space sickness), and balance disorders such as Meniere's disease. 

 Highstein tried a number of fish before choosing the toadfish as a model when he came to the MBL in the 1970s as a postdoc.

 "It was a matter of convenience," he remembers. Toadfish were readily available. They were hardy enough to survive in the lab. And they had an important anatomical advantage over other fish: Their broad, flat head-- the ungainly feature that gives Opsanus its monstrous pollywog look-- provides space enough for easy-to-sort-out neural wiring. In scup (and humans, for that matter), the nerves leading to and from the brain are intertwined in order to pass through a relatively smaller space.

 Highstein's long-standing interest in toadfish is in part responsible for the animal's current popularity at the MBL-- and elsewhere. Five other investigators have joined Highstein on an NIH-funded study of toadfish ears: Richard Rabbitt from the University of Utah; Michael Miller, an engineer from Washington University; Richard Fay, a psychologist from the MBL and Loyola University of Chicago; Gay Holstein, a morphologist from Mount Sinai School of Medicine in New York; and the MBL's Robert Silver, who is imaging Opsanus' vestibular apparatus.

 Other toadfish work at the MBL is being done by yearround investigator Neal Cornell, who uses Opsanus as a model for studies of toxicology, pollution, and drug metabolism. Summer investigator Sherwin Cooperstein, of the University of Connecticut Health Center, has studied insulin secretion in toadfish for many years.

 The insulin studies, Highstein says, were probably already going on when he arrived in the 1970s--which is why he found toadfish in the old marine resources building when he went looking for a model for vestibular system studies.

 But those studies were not the first MBL studies on toadfish either. Cornelia Clapp wrote a paper on movement-sensing hair cell receptors located outside the toadfish ear around 1900. Clapp was the one who gave toadfish its taxonomic name Opsanus tau, Highstein says, apparently because part of the animals' movement-sensing apparatus is a canal shaped like the Greek letter tau.