This is the first deep-sea fish known to be a mouthbreeder
Most fish are broadcast spawners, casting their eggs and sperm in clouds and leaving their young to develop alone. But a tiny minority — about 2 percent — are “mouthbreeders,” keeping their fertilized eggs (and sometimes hatchlings) protected in their mouths. Now, a study reveals the first fish known from the deep sea to mouthbrood, researchers report February 27 in Scientific Reports. In 2015, ichthyologist Randy Singer, now at the University of Michigan Museum of Zoology in Ann Arbor, was identifying fish spotted by a remotely operated underwater vehicle for the U.S. National Oceanic and Atmospheric Administration’s Okeanos Explorer ship. A red-glinting fish flashed by the vehicle’s camera some 500 meters deep, near Puerto Rico. Later, Singer identified the fish as a parazen (Parazen pacificus), a poorly known species found in the deep West Atlantic and West Pacific. Upon learning about parazens’ disjointed range, Singer suspected these fish were actually multiple species,...