Meet our newfound glow-in-the-dark neighbour

The new Pacific-living species are at top and bottom, with the already-known Atlantic species at middle. Photo / Poulsen et al

Scientists have discovered two new species of a glow-in-the-dark fish family found deep in waters near New Zealand.

Researchers from the Australian Museum and the Greenland Nature Institute found they'd happened upon two new species of the bioluminescent deep-sea "barreleyes" family when they looked at the patterns of pigmented "glow-blocking" scales on the underside of barreleyes caught near New Zealand, American Samoa and in the Atlantic.

The scientists saw three different pigment patterns that suggested three distinct species - which was confirmed when looking at the genetics - and revealed that the two new species were found only in the Pacific, not in the Atlantic.

Because of their rareness and fragility, barreleye fish are not well described, although previous work suggested the family included 19 species.

Some species have organs called "soles" along their bellies, covered with pigmented scales that control the light emitted from an internal organ.

The Australian Museum's Dr Jan Poulsen and colleagues compared sole pigment patterns and mitochondrial genomes of four specimens of a sole-bearing barreleye fish caught on recent research cruises near American Samoa and New Zealand with long-preserved specimens caught near the mid-Atlantic ridge and Australia.

The examination of fresh material, compared with preserved material, proved crucial, as long-time preservation could obscure the pigment patterns that showed variation between species.

The researchers found three different pigment patterns on the light-controlling organs of the fishes studied, suggesting that they were three distinct species.

This conclusion was backed by differences in mitochondrial DNA and thus, the team confirmed the new species of the genus Monacoa, naming them M. niger and M. griseus.

Most sole-bearing barreleye fish are caught at depths where some sunlight penetrates, and the researchers suggest that light emitted by the sole may be used for counter-illumination to camouflage it against the slightly sunlit water, as well as for communication.

The new communication system observed in sole-bearing tube eyes showed these fishes were masters at controlling light emission on multiple levels.

"This new study on the deep-sea has shown unknown biodiversity in a group of fishes previously considered teratological variations of other species," Poulsen said.

"The different species of mirrorbelly-tube eyes can only be distinguished on pigmentation patterns that also constitutes a newly discovered communication system in deep-sea fishes."