The lighter areas on the skin of this chain cat shark contain a special molecule that absorbs the ocean’s blue light and turns it into green light.
Scientists have figured out why certain species of shark can absorb blue light in the ocean and essentially turn the light green, making them appear to glow. It’s due to a newly discovered family of small-molecule metabolites in the lighter parts of the sharks’ skin, according to a new paper in the journal iScience.
The phenomenon is known as biofluorescence, not to be confused with a related phenomenon, bioluminescence.
These are not “glow in the dark” sharks. Fluorescence is a phenomenon where light is absorbed and emitted at a longer wavelength.
“There are some bioluminescent sharks, and some animals have both properties, making it even more confusing,” said co-author Dave Gruber of the City University of New York.
“The simplest way to think about it is that some animals make their own light [bioluminescence] and some transform light [biofluorescence].”Most bioluminescent species thrive deep in the ocean, below the so-called “photic zone,” where no photons from the sun can reach, so the animals must make their own light.
“Biofluorescence is more of a shallow phenomenon, because that’s where the light is,” said Gruber.
Gruber became interested in studying sharks several years ago, when he discovered that biofluorescence was surprisingly common in more than 180 marine species, some of which were species of sharks and stingrays. Prior to that, most biofluorescence studies had focused on jellyfish and corals.
“There has been a lot of debate about the function of fluorescence in corals, but sharks are animals with very strong visual senses,” said Gruber—something the corals are definitely lacking.
He and Crawford were working on another project when Gruber mentioned the existence of biofluorescent sharks, and it became a joint passion project, even though they didn’t have funding at first.
Of all Philip Henry Gosse’s works, the most successful was The Aquarium, in which he described his observations of coastal life and — a year after establishing the first public aquarium at the London Zoo — gave his readers instructions on how to build a miniature ocean of their very own.
A saltwater aquarium, he asserted, was the perfect way to get acquainted with the peculiar creatures of the ocean without having to descend into the depths using complicated diving equipment.
He was amused by a French zoologist, Henri Milne-Edwards, who stalked around at the bottom of the Mediterranean wearing a “water-tight dress, suitable spectacles, and a breathing tube” in order to take a closer look at the submarine world.
All this was so much easier to achieve, Gosse proclaimed, in the safe environment of one’s own four walls. In his many long-winded reports about his coastal excursions, Gosse told his readers that the aquarium was the objective, but that many obstacles still had to be overcome.
One’s relation with nature required a cautious and respectful approach, for its exploration was, in Gosse’s mind, a spiritual exercise.
For Gosse, religion and natural science went hand in hand: “it brings us, in some sense, into the presence of God”, he said, “or rather it gives us cognizance of Him, and reveals to us some of his essential attributes”.
The German ichthyologist M.H.C. Lichtenstein described the goliath grouper as Serranus itajara in an 1822 publication regarding the natural history of Brazil.
In an 1884 work, “The fishes of the Florida Keys,” David Starr Jordan proposed the inclusion of the goliath grouper in Epinephelus (Bloch 1793) and this combination remains in use today. Of incidental note is the fact that various authors have incorrectly spelled the specific epithet “itajara” as “itaiara.”
The genus name comes from the Greek epinephelos translated as cloudy. Synonyms of E. itajara include Serranus guasa Poey 1860 and Serranus quinquefasciatus Bocourt 1868.
A number of authors treat the name Promicrops itajara as valid taxonomy for the goliath grouper.
The goliath grouper occurs in the western Atlantic Ocean from Florida south to Brazil, including the Gulf of Mexico and the Caribbean Sea.
It is also found in the eastern Atlantic Ocean, from Senegal to Congo although rare in the Canary Islands.
The species is also present in the eastern Pacific Ocean from the Gulf of California to Peru.
Coelacanths have remained almost unchanged for 420m years.
Photograph: Alamy Stock PhotoBright blue,
Older than dinosaurs and weighing as much as an average-sized man, coelacanths are the most endangered fish in South Africa and among the rarest in the world.
Barely 30 of these critically-endangered fish are known to exist off the east coast of South Africa, raising concern that a new oil exploration venture in the area could jeopardise their future.
Coelacanths, whose shape has remained almost unchanged for 420m years, captured world attention when the first living specimen was caught off the port city of East London in 1938.
This discovery was followed by the subsequent capture of several more off the Comoros islands in the early 1950s, confirming that coelacanths were definitely not extinct.Shelf Life:
”The Sodwana coelacanths are about 40km from the northern boundary of the Eni exploration area and nearly 200km north of the first drilling sites, but Venter said oil spills spread far and swiftly.His concerns have been echoed by the coelacanth expert Prof Mike Bruton, who said the fish are specialist creatures, sensitive to environmental disturbance.
Photograph: Simon Maina/AFP/Getty Images
“Anything that interferes with their ability to absorb oxygen, such as oil pollution, would threaten their survival. The risk of oil spills or blowouts during exploration or futur is a source of serious concern.”