How ‘devil’ rays got their horns


This September 2017 video says about itself:

Scott and Ellis get a once in a lifetime chance to get up close underwater with Giant Manta Rays in the pristine waters of Raja Ampat, Indonesia.

From San Francisco State University in the USA:

How the devil ray got its horns

Biologists reveals origins of a distinctive fish feature

November 29, 2018

If you ever find yourself staring down a manta ray, you’ll probably notice two things right away: the massive, flapping fins that produce the shark cousin’s 20-foot wingspan and the two fleshy growths curling out of its head that give it the nickname “devil ray”. A new San Francisco State University study shows that these two very different features have the same origin — a discovery that reflects an important lesson for understanding the diversity of life.

“Small tweaks in early development can contribute to larger differences in how animals’ bodies are laid out,” explained San Francisco State Professor of Biology Karen Crow.

For Crow and her graduate student John Swenson, now a Ph.D. student at the University of Massachusetts Amherst, the hornlike “cephalic lobes” of manta rays represented a curious problem. All types of fish have two sets of paired appendages, like fins. But somewhere in their evolutionary past, a group of rays appeared to acquire a third set. These cephalic lobes are used for feeding, allowing some species to grapple with shellfish while helping species like manta rays more efficiently hoover up tiny plankton as they flap their way through the open ocean. What wasn’t clear was just where these fleshy face funnels came from.

To investigate, the researchers studied the embryos of cownose rays, the closest relatives of the massive mantas. They took samples of genetic material at different stages of the rays’ growth to see which genes were active during fin development, akin to peeking at the growing ray’s assembly instructions. The team examined hundreds of genes and paid special attention to several “Hox” genes, which contain instructions for growth and development of fins and limbs. It’s a group of genes crucial to development in all animals, including humans.

The team’s results showed that the ray’s horns aren’t a third set of appendages at all — they’re simply the foremost bit of fin, modified for a new purpose. They found that the same Hox genes that guide development of the rays’ cephalic lobes also play the same role in the fins of a closely related ray species, the little skate, which doesn’t have cephalic lobes.

In fact, the way the horns develop is surprisingly simple. All it takes is a tiny notch that deepens and widens as the manta grows, separating each fin into two distinct parts: one for feeding and the remainder for swimming. The team published their results in the journal Frontiers in Ecology and Evolution on Nov. 13.

The researchers say that the findings support a consensus that’s emerging among scientists who study evolution: Strange, novel features in nature can often arise from tiny evolutionary tweaks. “Whatever genetic changes occurred, there were far fewer than what we expected,” said Crow. A devil ray isn’t so different from its hornless cousins. And that lesson applies on a broader scale, too, she explains.

“We share the same genetic toolkit with all the other animals — and we share many of our genes with all living things,” Crow said.

Jeff Klomp, a research associate at the University of North Carolina, Chapel Hill, and Robert Fisher, a marine scientist and fisheries specialist at the College of William and Mary, were co-authors on the study.

Florida, USA cownose ray migration, new study


This November 2015 video from Florida in the USA says about itself:

Thousands of cownose rays caught on drone video near Marco Island

Thousands of cownose rays flocked to Marco Island over the weekend, causing quite a spectacle in the waters surrounding the Pelican Pier, not far from the Jolley Bridge.

From the Smithsonian in the USA:

For the first time, biologists track cownose rays to Florida and back

Summer and winter habitats pinned down in longest cownose ray migration study on Atlantic

August 23, 2018

Every summer, cownose rays stream into Chesapeake Bay to mate and give birth to their pups. When autumn comes, they disappear — presumably to migrate south, but no one knew for certain where they spent the winter. Now, after a three-year tagging study published Aug. 23 and led by the Smithsonian Environmental Research Center (SERC), scientists have solved the mystery. Cownose rays all along the Atlantic winter near Cape Canaveral, Florida, and it is likely they return to the same spots each summer.

Cownose rays are large stingrays native to the Chesapeake, with dark brown or olive-gray backs and white bellies. They reproduce slowly. Most mothers give birth to only one pup a year, and they do not mature until age 7 or 8, making them vulnerable to intense fishing or sudden population declines. And yet cownose rays have been dogged by controversy. In the early 2000s, they were saddled with partial blame for oyster declines because their diet includes shellfish. (Later studies cleared their names. Oysters had been declining years before cownose rays became more abundant.) Later, in 2015, bowfishing tournaments for cownose rays began raising alarm among some Marylanders. In response, the Maryland government voted to become the first state to create a fishery-management plan to conserve the cownose ray.

“Because of the slow birth rate, we know that if we don’t manage them, and instead harvest them in a way that heavily impacts the population and causes a population decline, it’ll take a long time for them to recover”, said Matt Ogburn, SERC marine biologist and lead author of the study. “If we lose something important, we could lose it for decades.”

The new study, published in Marine Ecology Progress Series, marks the first time scientists have tracked cownose ray migrations along the Atlantic coast for a full year or more. Knowing where they go every year will help fill in some longstanding knowledge gaps about the rays, as Maryland officials decide how to manage them. It is part of the Smithsonian’s new Movement of Life Initiative. Scientists from the Virginia Institute of Marine Science (VIMS) and Savannah State University also joined the effort.

To tag the rays, scientists spent three summer and fall field seasons teaming up with commercial fishers. These fishers were not trying to catch cownose rays, but the animals often appear as accidental bycatch in their pound nets or haul seines. Many of the fishers had worked with the scientists before, partnering with VIMS co-author Robert Fisher or on SERC’s crab-tagging studies.

“Collaborative efforts with commercial fishers are built on trust, straight talk and inclusion to investigate common problems and opportunities”, said Fisher, who has studied cownose rays for nearly three decades.

After transferring the rays to a holding tank, the researchers gave them general and local anesthesia and inserted a small acoustic tag inside them. Once the rays had recovered from surgery, the scientists released them back into the water. As the rays continued their journeys, the tags emitted a series of “pings” unique to each ray. An array of hundreds of receivers lines the Chesapeake and the Atlantic coast, waiting to pick up their signal. These receivers were placed by dozens of scientists from institutions along the East Coast, all sharing data on different species. If a ray passed within half a kilometer of a receiver, the receiver would record data about the ray’s location. Then the data were shared through the Atlantic Cooperative Telemetry Network and Florida Atlantic Coast Telemetry Network.

The teams tagged 42 rays total. Most were tagged in Virginia, with five in Maryland and two in Georgia. Of those rays, 28 had their signals detected multiple times over a period longer than 90 days, enough time for scientists to get a sense of their migration behavior.

Regardless of where scientists tagged the rays, every ray they detected in winter went to the same spot: a region just off the coast of Cape Canaveral. The greater challenge was figuring out if cownose rays go back to the same places each summer. While most rays returned to the same regions where scientists tagged them the previous year — some even to the same rivers — many rays were tagged in the fall, when they might have already left their summer homes. Only five rays sent out location signals for both summer 2015 and summer 2016. Four of those rays (three from Virginia and one from Georgia) returned to their original regions. The fifth spent both summers in the Chesapeake, but the first summer in Virginia and the second in Maryland.

This pattern could make conservation even more critical. If cownose rays are returning to the same places each summer, that means the Chesapeake likely has its own distinct population. Intense fishing of rays in the Chesapeake, especially during summer, could wipe out a large slice of the species’ genetic diversity.

“If they’re really tied to one specific place, then you’ll be removing a whole piece, a whole unique segment, from the population”, Ogburn said.

While scientists have unraveled one mystery about cownose ray migrations, there are still many unknowns surrounding the animals. Not least, the authors emphasized, is their role in the Chesapeake Bay as a whole. By turning over the sediment, a bit like tilling a garden, they could play a vital role for organisms like shellfish and crabs that live on the bay floor. As Maryland develops the first official management plan for cownose rays, studies like this will offer more guidance on how to manage one of the most enigmatic creatures in the Chesapeake.

Dinosaur age ‘alga’, ‘squid’ fossil is really a fish


A photo of the Platylithophycus cretaceum specimen. The scale bar is 5 centimeters. Credit: © Mike Eklund

From the American Museum of Natural History in the USA:

First an alga, then a squid, enigmatic fossil is actually a fish

New study suggests that Cretaceous fossil discovered 70 years ago is a large ray

April 16, 2018

A fossil slab discovered in Kansas 70 years ago and twice misidentified — first as a green alga and then as a cephalopod —

Maybe misidentified a third time: as a Angiospermopsida seed plant

has been reinterpreted as the preserved remains of a large cartilaginous fish, the group that includes sharks and rays. In a study published in the Journal of Paleontology, American Museum of Natural History researchers describe the fishy characteristics of the animal, which lived between 70-85 million years ago.

“There are many examples of temporarily misplaced taxa in paleontological history, including ferns that were once thought to be sponges and lungfish teeth thought to be fungi“, said the lead author, Allison Bronson, a comparative biology Ph.D.-degree student in the Museum’s Richard Gilder Graduate School. “In this case, the misidentification didn’t happen because of a lack of technology at the time — scientists familiar with cartilage structure could easily see this was a chondrichthyan fish. The researchers used reasonable arguments for their interpretations, but didn’t look outside of their own fields.”

The enigmatic specimen, Platylithophycus cretaceum, is roughly 1.5-feet long by 10-inches wide and from the Niobrara Formation in Kansas. The Niobrara Formation is one of the most diverse fish-fossil sites in North America, preserving late Cretaceous animals that lived in and around the Western Interior Seaway, a broad expanse of water that split North America into two land masses.

In 1948, two paleobotanists from the Colorado School of Mines and Princeton University compared the texture of the fossil slab with that of green algae. They described two parts of a plant: surfaces covered with hexagonal plates, which they called “fronds”, and supposedly calcium carbonate-covered thread-like filaments. In 1968, two researchers from Fort Hays Kansas State College studying cephalopods from the Niobrara Formation compared the specimen with a cuttlefish, based primarily on its textural similarities to a cuttlebone — the unique internal shell of cuttlefish. The reclassification made Platylithophycus the oldest sepiid squid then on record.

In both of these earlier studies, the hard tissue was assumed to be composed of calcium carbonate, but no tests were performed. For the new study, Bronson and co-author John Maisey, a curator in the Museum’s Division of Paleontology, applied a small amount of dilute organic acid to the specimen — a method that has been widely used in paleontology since the time of the initial description of Platylithophycus. If there is a reaction, the fossilized material is likely made from calcium carbonate. But if there is no reaction, which was the case when Bronson and Maisey performed the test, it is likely made from calcium phosphate, as are the fossilized skeletons of cartilaginous fish like sharks and rays.

The most obvious clue that Platylithophycus was a cartilaginous fish are the hexagonal plates on the surface of the specimen. After taking a closer look with a scanning electron microscope, Bronson and Maisey reinterpreted that feature as tessellated calcified cartilage, found on both extinct and living sharks and rays. The new study suggests that the “filaments” earlier described are actually part of the gill arches, made up of tessellated cartilage. Gill arches are cartilaginous curved bars along the pharynx, or throat, that support the gills of fish. The “fronds” are reinterpreted as gill rakers, finger-like projections that extend from the gill arches and help with feeding.

“We think this was a rather large cartilaginous fish, possibly related to living filter-feeding rays such as Manta and Mobula“, Maisey said. “This potentially expands the range of diversity in the Niobrara fauna.”

But because this fossil only preserves the animal’s gills and no additional identifying features like teeth, it cannot be given a new name or reunited with an existing species. So until then, this fish will still carry the name of a plant.

Deep-sea rays use hydrothermal vents for incubating eggs


This video says about itself:

Deep-Sea Skates Incubate Eggs Near Hydrothermal Vents | Nautilus Live

8 February 2018

In June 2015, a team of researchers aboard E/V Nautilus made a surprising discovery while exploring the seafloor northwest of the Galapagos Islands. Large numbers of skate egg cases were observed near hydrothermal vents emitting volcanically-heated fluids. Researchers believe the warmer water helps to incubate and speed development of the embryos–the first time this behavior has been observed in marine animals. The Bathyraja spinosissima, commonly known as Pacific white skate, is a relative of sharks and rays. As one of the deepest living skate species, this species is rarely seen but has been documented from the Galapagos Islands to the Pacific Northwest.

The research team from Charles Darwin Research Station, University of Rhode Island, and the Galapagos National Park Directorate collected video surveys and specimens using ROV Hercules, recently publishing their findings in Scientific Reports.

From Penn State university in the USA:

Deep-sea fish use hydrothermal vents to incubate eggs

February 12, 2018

Summary: An international team of researchers have discovered egg cases of deep-sea fish near hydrothermal vents. The team believes that deep-sea skates, a relative of sharks and rays, use the warm water near the vents to accelerate the typically years-long incubation time of their eggs.

Some deep-sea skates — cartilaginous fish related to rays and sharks — use volcanic heat emitted at hydrothermal vents to incubate their eggs, according to a new study in the journal Scientific Reports. Because deep-sea skates have some of the longest egg incubation times, estimated to last more than four years, the researchers believe the fish are using the hot vents to accelerate embryo development. This the first time such behavior has been seen in marine animals.

“Hydrothermal vents are extreme environments, and most animals that live there are highly evolved to live in this environment,” said Charles Fisher, Professor and Distinguished Senior Scholar of Biology at Penn State and an author of the paper. “This study is one of the few that demonstrates a direct link between the vent environment and animals that live most of their life elsewhere.”

Among the least explored and unique ecosystems, deep-sea hydrothermal fields are regions on the sea floor where hot water emerges after being heated in the ocean crust. In their study, an international team of researchers, led by Pelayo Salinas-de-León of the Charles Darwin Research Station, used a remotely operated underwater vehicle (ROV) to survey in and around an active hydrothermal field located in the Galapagos archipelago, 28 miles north of Darwin Island.

“The first place the ROV landed on the sea floor was on a ridge, in the plume of a nearby hydrothermal vent that we had specifically come to investigate — a black smoker,” said Fisher. “When we panned the camera down, we found something we did not expect: These giant egg cases, also known as mermaid purses. And we found several layers of them, indicating that whatever was laying these eggs had been coming back to this spot for many years to lay them. As the dive progressed, we saw more and more of these egg cases and realized that this was not the result of a single animal, but rather a behavior shared by many individuals.”

The researchers found 157 egg cases in the area and collected four with the ROV’s robotic arm. DNA analysis revealed that the egg cases belonged to the skate species Bathyraja spinosissima, one of the deepest-living species of skates that is not typically thought to occur near the vents. The majority — 58 percent — of the observed egg cases were found within about 65 feet of the chimney-like black smokers, the hottest kind of hydrothermal vents, and over 89 percent had been laid in places where the water was hotter than average. The researchers believe that the warmer temperatures in the area could reduce the typically years-long incubation time of the eggs.

While several species of reptiles and birds lay their eggs in locations that optimize soil temperatures, only two other groups of animals are known to use volcanically heated soils: the modern-day Polynesian megapode — a rare bird native to Tonga — and a group of nest-building neosauropod dinosaurs from the Cretaceous Period.

Because of their long lifespan and slow rate of development, deep-water skates may be particularly sensitive to threats to their environment, including fisheries expanding into deeper waters and sea-floor mining. Understanding the development and habitat of the skates is vital for developing effective conservation strategies for this poorly understood species.

“The deep sea is full of surprises,” said Fisher. “I’ve made hundreds of dives, both in person and virtually, to deep sea hydrothermal vents and have never seen anything like this.”

Manta rays helped by small fish


This video says about itself:

Manta Rays Use Tiny Fish to Help Them Stay Clean

12 January 2018

Wrasse perform a vital cleaning function for other fish, by ridding their bodies of dead cells and parasites. Their biggest customers–literally and figuratively–are the massive manta rays. From the series: David Attenborough’s Great Barrier Reef: Visitors.

Manta rays have an unusual mouth filter that resists clogging. Instead of snagging in the filter, plankton ricochets toward the manta’s throat. By Laurel Hamers, 2:05pm, September 26, 2018.

Mobula rays video


This BBC video says about itself:

Filming Hundreds Of Mobula Rays At Night – Blue Planet II Behind The Scenes

The Blue Planet II underwater camera crew use new camera technology to film hundreds of Mobula rays in almost complete darkness. As the rays glide through the dark water, their movement causes plankton to glow which is picked up my the camera.

Thornback ray reintroduction in Dutch Zeeland


This video is called Thornback ray or thornback skate (Raja clavata).

Dutch daily Trouw reports today about thornback ray reintroduction in Dutch Zeeland province.

On Saturday 14 October 2017, five young thornback rays, raised in aquariums, will be brought to an oyster farm in Yerseke town. There, they will get used to the Oosterschelde estuary water. In a few weeks’ time, they will be freed. Later, more, up to 1000, young thornback rays will be freed. It is hoped that they will be a sustainable thornback ray population in the Oosterschelde; where they had become extinct. This species is sexually mature after eight years. Will they survive now? We don’t know yet.

Sharks, rays live longer than estimated before


THis 2014 video from the USA says about itself:

Stingrays and Manta rays come in many shapes and sizes… But one of the coolest rays in all the ocean has to be the giant Shark Ray.

In the front they are broad like a ray, but the back section they are all shark with dual dorsal fins. How cool is that! Also known as a bowmouth guitarfish, this large species can reach a length of 2.7 m (8.9 ft) and weigh up to 135 kg (298 lb).

WHERE TO SEE RAY SHARKS IN THE USA In one of the biggest resorts in town, there’s a major Aquarium with full-grown Shark Rays in it. It’s called the “Shark Reef” and its main tank is filled with 1.3 million gallons of water. This Aquarium displays all kinds of sharks, rays, fish, reptiles, even a green sawtooth shark — but the real celebrities here are the Shark Rays….

Just step inside what they call the Shark Tunnel and within seconds you will have a very up close and personal encounter – guaranteed!

SHARK RAYS ARE A THREATENED SPECIES. Shark Rays are not dangerous to humans. They like to eat crabs or lobsters and stuff like that but their numbers in the wild are dwindling due to overfishing. They are killed for the shark fin on top. It’s the main ingredient in Shark Fin Soup which is popular in certain parts of the world. Attempts to breed these amazing creatures in captivity so far has been a failure. Seven pups born at the Newport Aquarium in Kentucky all died within a few months of their birth.

From James Cook University in Australia:

Sharks and rays live a lot longer than we thought

September 29, 2017

A James Cook University researcher has found that sharks and rays live a lot longer than we thought — some twice as long as previously estimated.

Dr Alastair Harry looked at 53 different populations of sharks and rays that scientists had already intensely studied. He said in nearly a third of populations the studies had underestimated the animals’ ages.

“Questions arose over methods of ageing sharks after it was found that grey nurse sharks can live up to 40-years-old, double the length of time first thought, and the age of New Zealand porbeagle sharks had been underestimated by an average of 22 years,” he said.

Dr Harry said scientists usually measure shark age by counting growth rings in their vertebrae. These measurements are confirmed by tagging animals and injecting them with a fluorescent marker or by measuring carbon accumulated in the animals from atmospheric testing of nuclear weapons in the 1950s.

“Age underestimation appears to happen because the growth rings cease to form or become unreliable beyond a certain size or age. Across the cases I studied age was underestimated by an average of 18 years, and up to 34 years in one instance. From the amount of evidence we now have it looks like the problem is systemic rather than just a few isolated cases,” he said.

Dr Harry said accurate age estimation was important because it was used to manage fishery stocks.

He said the underestimation of longevity in orange roughy, a deep-sea fish, led to overly optimistic estimates of stock productivity, contributing to serious, long-term ecological and socio-economic impacts.

Dr Harry said sharks and rays are less commonly targeted by commercial fishers, but are still often caught as bycatch. That means the impacts of age underestimation may well take longer to become apparent.

“It could lead to inefficient prioritisation of research, monitoring and management measures. If it’s as widespread and common as it seems from this study, the impacts could also be substantial from a wider scientific perspective, affecting the many disciplines that also use baseline life history data,” he said.

To shine light on and conserve rare shark, ray, and chimaera species (chondrichthyans), SFU researchers have developed a fully-resolved family tree and ranked every species according to the unique evolutionary history they account for: here.