A team of researchers from the Australian Museum in Sydney identify  two new species of bioluminescent deep-sea fish nicknamed “barreleyes.” These recently discovered species are part of the family Opisthoproctidae, a rare and fragile group of fish that remains understudied.

As stated in their study published on August 10 in the journal PLOS ONE, the research team caught the fish during their missions close to American Samoa, New Zealand, the mid-Atlantic ridge and Australia. They compared each fish for their pigment patterns and mitochondrial genomes.

The team realized that each fish sports a different pigment pattern on the organs that control light. Due to this, they speculated that the barreleyes were not the same species, which was later confirmed by their mitochondrial DNA analysis.



They named the two new species as Monacoa niger and M. griseus. Apparently, these fish can only be found in the Pacific but the previously known ones were only found in the Atlantic.

The research team explains that the Opisthoproctidae family includes 19 species. Some species have soles, which are organs along their bellies covered with pigmented scales that regulate the light produced from their internal organs.

Although not much is known about the fish, scientists assume that the light emitted through the sole is used for counter-illumination so the fish can camouflage itself in an environment that only receives some sunlight. They add that their sole-bearing tube eyes demonstrate that these species can control the light they emit skilfully.

“This new study on the deep sea has shown unknown biodiversity in a group of fish previously considered teratological variations of other species,” points out the study’s researcher Jan Poulsen from the Australian Museum. “The different species of mirrorbelly tube eyes can only be distinguished on pigmentation patterns that also constitute a newly discovered communication system in deep-sea fish.”