Team Uncovers the Physiology Behind the Hour-Long Mating Call of Midshipman Fish

Midshipman fish can generate a mating call that emits continuously from their bodies for a full hour. Biologists have puzzled over how this was possible, as the call requires the fish to contract and relax muscles around their swim bladder very quickly—360,000 times in an hour, to be precise—seemingly too fast for the necessary pumping of calcium ions required for muscle contraction. A new study led by Penn researchers provides an explanation for this display of physiological fortitude. In an investigation featured on the cover of the Journal of General Physiology, the team discovered that the fish release very small amounts of calcium for each muscle contraction, allowing for a quick re-uptake that enables the process to continue uninterrupted to produce a sustained hum.

“These findings shed light on these fascinating creatures and this extraordinary ability,” says Lawrence C. Rome, Professor of Biology. “And in a broader sense the study opens our eyes to the idea that calcium doesn’t always have to go all the way up and down in order to maintain muscle activity. It’s something that may apply to other animals that move at high speeds.”

Rome collaborated on the work with Stephen Hollingworth and Stephen M. Baylor of the Perelman School of Medicine; James O. Marx of the School of Veterinary Medicine; and Frank E. Nelson of Temple University

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