Scientists have captured the first-ever footage of a barreleye fish, Winteria telescopa, alive in its natural habitat. The rare deep-sea species was filmed during a month-long expedition to the Doldrums Megatransform and Fracture Zone in the Atlantic Ocean, one of the least explored parts of the region.
Researchers from the Schmidt Ocean Institute used the remotely operated vehicle SuBastian to spot the fish at a depth of approximately 2,300 feet (710 meters). This region, known as the mesopelagic or 'twilight zone,' receives only a faint glow of sunlight.
Barreleye fish are distinguished by their transparent heads, which allow a view of their internal eye structure. Their tube-shaped eyes are adapted to point upwards, enabling them to detect the faint light filtering from the surface and spot the bioluminescence of prey in the darkness. Scientists believe this transparent shield may also protect their eyes from stinging cells when feeding.
The transparent dome covering the fish's head often collapses when specimens are brought to the surface, meaning most prior knowledge of the species came from damaged samples. Observing the fish in its natural environment provides a rare opportunity to study its behavior.
Barreleye fish typically measure between 4 to 6 inches (10 to 15 centimeters) in length. Scientists think they are opportunistic feeders, sometimes consuming small animals found in the tentacles of jellyfish and siphonophores.
The expedition also led to other significant discoveries. The team identified two previously unknown hydrothermal vent fields, which harbor thriving ecosystems independent of sunlight. Additionally, researchers encountered two elusive bigfin squid, a deep-sea species characterized by its extremely long, thread-like tentacles.
Dr. Paula Zapata Ramirez, an assistant professor at the Universidad Pontificia Bolivariana, stated that the expedition's findings contribute to a deeper understanding of ecosystems in one of the Atlantic Ocean's least explored regions. "Every sample, every image, and every discovery brings us one step closer to understanding the hidden parts of our planet," she said.