Divers exploring warm waters around the world often encounter Chilean devil rays, gentle marine creatures that can grow up to ten feet long.
Scientists have just discovered that the rays harbor an impressive secret, however: they regularly undertake epic dives more than a mile deep.
These remarkable dives came as a surprise to researchers who reported the finding today in Nature Communications. In retrospect, they note, the rays’ physiology did hint at this ability.
Chilean devil rays possess a special organ called the retia mirabilia, which is also found in deep-diving species such as great white sharks. In those animals, the veined structure fills with warm blood that exchanges heat between vessel walls.
This helps to keep the marine creatures’ brain warm when they descend to freezing depths. But Chilean devil rays, researchers assumed, spent all of their time at the surface. Why would they need such a structure?
To solve the puzzle, an international team of marine biologists attached satellite tags to 15 Chilean devil rays captured off the northwest coast of Africa, near the Azores archipelago. The team monitored the rays’ movements for nine months and found that the animals were tremendously active.
They sometimes traversed up to 30 miles of ocean per day, with each covering a distance of up to 2,300 miles over the nine-month period. Even more impressive, however, was the rays’ diving abilities.
They regularly dove below 1,000 feet, with a maximum-recorded depth of 6,062 feet. This means that Chilean devil rays undertake some of the deepest dives ever recorded for marine animals, the team reports.
The journeys into the deep seem to be no sweat for the animals. One individual, for example, dove nearly 4,600 feet six days in a row, and overall, the rays spent more than five percent of their time in deep water.
The deep dives explain the presence of the previously enigmatic retia mirabilia, the team writes. At the depths recorded by the trackers, rays would encounter temperatures as chilly as 37˚F, so the extra flush of warm blood provided by that organ likely makes those dives possible. Additionally, the researchers found that the rays spend more time basking near the water’s warm surface both one hour before and one hour after a deep dive, implying that the animals are preparing for and recovering from encounters with the cold.
The rays aren’t undertaking these dives just for fun, of course. Based on the animals’ movement patterns—oftentimes a quick bee-line descent followed by a slower step-wise ascent—the researchers think they are probably foraging on fish or squid that live well below the surface.
The unexpected findings, the authors write, demonstrate “how little we know” about Chilean devil rays and the role they play in ocean ecosystems.
Given that these animals were recently listed as endangered (largely due to a growing demand for their gills by practitioners of traditional Chinese medicine), “this ignorance has significant conservation implications,” the team continues. As with any species, the more we know about them, the better equipped we will be for protecting them—and for knowing what we stand to lose should they disappear.
Bangkok-based photographer Visarute Angkatavanich (previously) continues to capture some of the most elegant portraits of fish we’ve seen.
His intimate, crystal-clear photos of Siamese fighting fish (betta) make it seem as though they are suspended in air instead of water.
Angkatavanich recently told Popular Photography that he only started photographing the fish after encountering them for the first time three years ago at a fish show and has since become obsessed with the different species which vary greatly in size, shape, and color patterns.
Limited edition prints of his work are now available through La Lanta Fine Art.
They can be as big as great white sharks, but that’s about as far as the comparison goes.
Their maximum speed is a lethargic 1.7 miles per hour, many are almost blind, and they are happy to eat rotting carcasses.
They may be common throughout the ocean, but you’ve probably never heard of them. Meet the Greenland shark.
Looking like nothing so much as a chunk of weather-beaten rock, Greenland sharks (Somniosus microcephalus) can grow up to 7.3 metres (24 feet) long, making them one of the largest of all fish, and the biggest in the Arctic.
But they prefer to live in deep, cold water, so humans rarely see them.
Studies in the Arctic have revealed a few snippets of information about Greenland sharks, and more data is now starting to come in from elsewhere.
It turns out that Greenland sharks are bizarre, and may be crucially important for the ocean ecosystem.
Greenland sharks only come close to the surface in places where the shallow water is frigid enough for them – primarily in the Arctic.
THIS IS ONE fish that will always be caught red-handed. Ok, bad pun, but it is an interesting fish.
Endemic to Tasmania’s eastern coast, the red handfish is so named because of its apparent use of its fins as hands, even using a type of walking motion on the seafloor.
It’s a benthic fish, preferring to hang around the sandy and rocky bottoms of the seafloor. They’ve been observed eating small crustaceans and worms.
There are two colour varieties – one with red embellishments (seen in the image above) and the other a right red all over. It grows from about 6cm to about 13.5cm long.
The red handfish was first discovered in the 1800s around Port Arthur.
In the 1980s a small population was found on the Actaeon Islands, south of Hobart, and the biggest population to date was found on a reef off Primrose Sands around Hobart (10 individuals) in the 1990s.
However, in a survey in 2005, no handfish were found in those areas.
They may be hanging on, because in 2010, three individuals were found in the Primrose Sands location.
Though the species hasn’t had a full, systematic survey of its numbers, it seems that populations are few and far between, and there’s likely to be not more than 1000 individuals in the wild, and likely only hundreds.
The red handfish was known as the Brachionichthys politus, but in 2009, it was re-categorised as Thymichthys politus.
Threats to red handfish include poaching for use as pets. Its low reproductive rate and low dispersal rate make is a challenge for the species’ survival. Fragmentation of the populations is also a challenge for reproductive success.