Vocal diversity in fishes and tetrapods. Credit: Nature Communications (2024). DOI: 10.1038/s41467-023-43794-y
For talkative midshipman fish—sometimes called the “California singing fish”—the midbrain plays a robust role in initiating and patterning trains of sounds used in vocal communication.
The midbrain in these fish, it turns out, may serve as a useful model for how mammals and other vertebrates, including humans control vocal expressions, according to Cornell behavioral research published Jan. 2 in Nature Communications.
“We have the evidence to show how that this part of the brain, the midbrain, is important to voice signaling,” said senior author Andrew Bass, the Horace White Professor of Neurobiology and Behavior in the College of Arts and Sciences. “It’s a brain region shared by all vertebrates, whether we are discussing a fish, a bird, or a person and is crucial to sound patterning and selection.”
The male midshipman fish make grunts, growls, and hums when mating or fending off foes, all originating from deep offshore in Northern California and the Pacific Northwest. During late spring and summer, they travel to shallow intertidal zones and guard unhatched eggs that grow into free-swimming fry located under rock shelters.
People report hearing the steady, echoing hum of a male midshipman fish chorus on quiet summer nights, a surprising phenomenon!
Mammals and other vertebrates emit sound and vocalize to communicate behaviors, but the midbrain responsible for initiating acoustic features—like patterned hums in these fish or the formation of sentences in humans—had largely gone unexplored.
Eric R. Schuppe, formerly a Cornell postdoctoral researcher in Bass’ laboratory, who now works at the University of California at San Francisco, led the research.
Video taken at nighttime under red‐light conditions illustrates a male humming from inside his artificial nest. Unlike a male that is producing agonistic vocalizations, humming males inflate their swim bladder during humming9. A consequence of inflating the swim bladder is that the male becomes positively buoyant; the terracotta top of the nest keeps him from floating to the surface of the tank. Note that the video only contains the near constant frequency portion of the hum, and not the hum onset. Credit: Nature Communications (2024). DOI: 10.1038/s41467-023-43794-y
Bass, Schuppe and other lab members found that midbrain periaqueductal gray neurons in the fish are activated in distinct patterns by the males during courtship calls, foraging and nest guarding duty.
The group confirmed that the periaqueductal gray neurons evoke output to the muscles that manage sound and the vocal features of courtship, as well as show patterning other kinds of calls.