Three new species of bioluminescent sharks have been discovered by a group of researchers in the deep waters off New Zealand. The researchers have defined these species as “glowing sharks.”

Research was carried out by doctors Jérome Mallefet and Laurent Duchatelet from the Earth and Life Institute’s Marine Biology department, part of the Université Catholique de Louvain in Belgium, together with Darren Stevens from the National Institute of Water and Atmospheric Research (NIWA) in Wellington, New Zealand.

Off the shores of the islands that make up this extraordinary country, known for the America’s Cup and for having been the filming location for “The Lord of the Rings”, there is an area of the ocean known as “Chatham Rise“, part of a now submerged ancient continent known as Zealandia. This is an important habitat for whales, extending for nearly 1000 km to the Chatham Islands and that, normally, goes no deeper than 1000m deep.

In a study published a few days ago in “Frontiers in Marine Science” and which can be read here, the scientists have demonstrated the existence of three species of deep water sharks which can glow in the dark. Bioluminescence is often seen as a spectacular event and rare in the oceans but, considering the vast depth of it and the presence of bioluminescent organisms in these areas, it is now increasingly obvious that making light in the deep has an important role in the structure of the largest ecosystem on our planet.

Bioluminescence, defined as the production of light visible to living beings, is a widespread phenomenon in a number of very different marine species. The species of sharks studied here were  Dalatias licha, Etmopterus lucifer and Etmopterus granulosus, in addition to  Zameus squamulosus. Even though these species were already known, their luminescence has only now been scientifically proven, along with the analysis of the biochemical mechanisms that cause it.

With a careful eye on the environment, the researchers did not capture specimens specifically for the study, but used specimens that had been captured as accessory prey in an investigation evaluating fishing for the New Zealand Ministry for Primary Industries.

Etmopterus lucifer (source: Frontiers in Marine Science)

The team has also demonstrated how the sharks researched are the only known bioluminescent organisms that control the amount of light they emit through hormones: melatonin sparks the glow, prolactin increases its intensity, while the alpha-melanocyte and adrenocorticotropic hormones inhibit it. Luminescence is then reached through thousands of photophores located in the skin, through a mechanism that is still not quite understood and through enormously complex structures.

They all emit a blue or blue-green light, sometimes in different parts of the body. The researchers have hypothesised a number of different reasons for this: counter-illumination towards other species, aposematism (when an animal senses a possibly dangerous enemy: this is done, for example, by poisonous animals), or conspecific recognition. To recognise equals, therefore, or maybe simply just to say hello.

Nature is incredible and never ceases to amaze. Imagine swimming in a dark sea that all of a sudden begins glowing blue in the shape of a shark. It could be the plot in a horror film, but I would be fascinated.

Photo source: Frontiers in Marine Science