Scientists have discovered a new species of luminous creatures in the Red Sea, living in colonies as garlands of ‘fluorescent lanterns’ and emitting a green glow.
During the study of the biodiversity of coral reefs of the archipelago Farasan in Saudi Arabia, south of the Red Sea, researchers observed marine life under the ultraviolet (UV) light with yellow filters.
They found “fluorescent lanterns,” that were very similar to hydrae, but unlike their distant relatives who lead a solitary life in fresh water new species from the Red Sea form spreading colonies decorating miniature shells of gastropods Nassarius margaritifer (20-35mm in length) with garlands of green lights.
These molluscs bury themselves in the sediment during the day and at night crawl out to the surface to hunt other invertebrates.
“Sea hydroids, unlike hydrae, are often found in colonies and can branch off tiny jellyfish,” said Vyacheslav Ivanenko, from the Lomonosov Moscow State University.
“The unusual green glow of these hydrozoas (presumably, a new species of the genus Cytaeis, whose body length reaches 1.5mm) was revealed in the peristomal area of the body,” Ivanenko said.
The researchers suggest that glow around the mouth of polyps may attract prey. “Fluorescent flashlights” may be visible to other invertebrates in the moonlight, and at sunset and sunrise.
Fluorescent proteins are widespread among the corals Anthozoa and hydroid jellyfishes, and also were found in some lancelets (Cephalochordata) and combjellies (Ctenophora).
According to zoologists, the fluorescence of hydrozoa is studied only in case of six species, in some cases – even at the early stages of development (eggs or jellyfishes before their attachment to the substrate).
The fluorescence of some of them is localised on the tentacles or stalk, and not around the mouth, or shifted to another part of the spectrum. The maximum of fluorescence emission of the new species of the genus Cytaeis is at 518 nanometre (nm).
“The comparison of the fluorescence of hydroid found in the Red Sea to those of other hydroids of the same genus, analysis of nuclear and mitochondrial DNA of the hydroid and evaluation of the data presented in the gene bank allowed to reveal the species-specific fluorescence of morphologically indistinguishable species of Cytaeis,” Ivanenko said.
“Thus, using hydroids as an example, the researchers first demonstrated the ability to use peculiarities of the localisation of the fluorescence for discrimination of similar invertebrates,” Ivanenko said.
“The fluorescence can be useful for quick identification of hardly recognisable species and for the studies of ecological peculiarities and distribution of hydroids and their hosts – molluscs,” said Ivanenko.
The study was published in the journal PLOS ONE.