Why male Toadfish's vibrating love muscle may fail to hit the right note with females

It may be supremely ugly with big pop eyes, but the oyster toadfish is proving the darling of marine biologists, who hope its superfast muscle will offer new clues for the treatment of human heart disease.

Hardly the cheetah of the seas, Opsanus tau is a sluggish mover, but its swimbladder muscle, which is used to produce a grunting call, is one of the fastest muscles around, relaxing and contracting up to 200 times a second - more than twice as fast as hummingbirds' wings.

Iain Young and his colleagues are keen to understand how this "super" muscle works and say knowledge of a muscle that is supremely adapted could shine valuable new light on muscular movement in general. It could prove useful in combating conditions such as heart disease or asthma in humans, where muscles do not relax properly.

The researchers are particularly interested in a calcium-binding protein, parvalbumin, which they believe may be crucial in the toadfish's swimbladder. Calcium is a trigger for muscle contraction.

"This protein has been known about for some time," says Young. "Now we can see it in the toadfish and are looking to understand its role in making this superfast muscle relax and contract. Is it a calcium shuttle, buffer or reservoir?

Other teams at the Marine Biology Laboratory in Massachusetts are working on different aspects of the toadfish, including understanding its hearing. They have even sent toadfish into space. But Young is concerned that climate change could mean the fish's days are numbered.

Male toadfish attract females by calling using the vibrating swimbladder. The frequency with which the swimbladder vibrates depends, says Young, on water temperature. Hence, the frequency with which the male toadfish sings changes over the mating season as the water temperature changes. Female toadfish, he adds, choose males based on their calling frequency and seem to change the frequency they select over the course of the mating season as the temperature increases.

Young fears a rapid change in ocean temperature, associated with global warming, could leave male fish singing at one frequency and female fish listening out for another.

"As a consequence of global warming, the Gulf Stream could move south," explains Young, meaning temperatures off the Massachusetts coast could drop. "The male toadfish may not make any noise at all at lower temperatures. The implications for the success of the toadfish may be very serious."