How sharks and rays evolve


This 21 May 2020 video says about itself:

Sharks and Rays by Annie Crawley

Sharks & Rays takes you on a journey to discover the wonders of sharks and rays from around the world. Join underwater photographer, filmmaker and ocean explorer, Annie Crawley to learn all about these amazing creatures. You learn the biology with complex information in easy to understand language.

Exclusive footage will have you diving with schooling hammerhead sharks, observing manta rays feeding, nurse sharks entering a state of tonic immobility, plus you will experience the first Shark Sanctuary in the world while diving in the blue waters of Palau. Whale sharks, hammerheads, great white sharks, electric rays, manta rays, reef sharks, mako sharks, dozens of species of sharks and rays from around our world’s ocean are explored in this program.

From Flinders University in Australia:

Ecosystem diversity drives the origin of new shark and ray species

May 19, 2020

Summary: Biologists how different oceanographic conditions in the Gulf of California and the Baja California Peninsula influenced formation of new species of sharks and rays.

What drives the evolution of new species of sharks and rays? Traditionally, scientists thought it required species to be separated by geographic or spatial barriers, however, a new study of elasmobranchs (the group of sharks and rays) has challenged this expectation — and found evolution is happening faster than many think.

Flinders University evolutionary biologists Dr Jonathan Sandoval-Castillo and Professor Luciano Beheregaray tested how different oceanographic conditions in the Gulf of California and the Baja California Peninsula (Mexico) influenced the formation of new species of guitarfish (genus Pseudobatos).

The team discovered four types, or ‘young species’, of guitarfish that have similar external appearance but are genetically different.

Each type of guitarfish appears to have adapted to one of the four separate regions of the Gulf of California. This promotes environmental tolerances which result in those guitarfish having improved odds for survival and reproduction in the region where they were born.

“We have shown that these four guitarfish species evolved quite quickly from the same common ancestor,” says Dr Jonathan Sandoval-Castillo.

“The process where several new species originate from one ancestor in a relatively short period of time is called adaptive radiation, and this is the first report of such a process in sharks and rays. Our results help changing the false popular belief that sharks and rays do not evolve, or only evolve very slowly,” says Prof Luciano Beheregaray.

These findings also have important implications for the management of exploited elasmobranch species, such as guitarfish in the Gulf of California which represents an important fishery for Mexico.

If these young species adapt and evolve to their local habitat conditions, they cannot be replaced by migrants from other habitats.

“If such species are incorrectly managed as a single stock, it can result in the over-exploitation and possibly extinction of the entire species.”

New Caledonian manta rays dive deep


This 2018 video says about itself:

“New Caledonia, Mother of the Coral Sea” features the incredible diversity of the Coral Sea in New Caledonia and how it provides for the people of New Caledonia — where nature and people are inextricably linked. The film features the different sides of New Caledonia — from Noumea, its capital city, to the magnificent Ouvea, referred to as “the closest island from Paradise”, and the bountiful life — turtles, sharks, manta rays, and large schools of fish — that blossoms in these waters, and are respected as culturally-significant totems.

Local community members, Marie-Lucette Taoupoulou, Pierre Kaouma, Marjorie Tiaou and Marino Tiaou take us through their world and their way of life. They share about their bond with nature and their aspirations of preserving this bond for generations to come. Conservation International and the Manta Initiative are working with partners to conserve the Coral Sea and its diversity — before it becomes endangered.

Narrated in French, with English subtitles, the film, produced by Blue Sphere Media, also features CI’s Marine Program Coordinator Mael Imirizaldu and Manta Initiative researcher Hugo Lassauce. …

The Mother of the Coral Sea has won a Silver Award for Best Documentary Short and an Honorable Mention for Best Cinematography at the Independent Shorts Awards in Hollywood, and has been officially selected to screen at the International Ocean Film Festival.

From PLOS:

Reef manta rays in New Caledonia dive up to 672 meters deep at night

Declining ray species dives much deeper than previously recorded, perhaps to access scarce zooplankton supplies

March 18, 2020

The first data collected on the diving behavior of reef manta rays in New Caledonia considerably extend the known depth range for this vulnerable species in decline, according to a study published March 18 in the open-access journal PLOS ONE by Hugo Lassauce of the University of New Caledonia, and colleagues. These results add new information on the habitat use of the species in a region where manta behavior has not previously been studied, and increase their known depth range by more than 200 m.

Reef manta rays (Mobula alfredi) are declining worldwide, in large part due to fishing pressure. More detailed information on the distribution and habitat use of the reef mantas is necessary to inform conservation and fisheries management measures to ensure the long-term survival of the species, now listed as vulnerable on the International Union for Conservation of Nature Red List. Pop-up satellite archival tags (PSAT tags) are one of the most effective methods to investigate fine-scale movements and habitat use in manta rays, but until now, there have been no such studies conducted in New Caledonian waters. In the new study, Lassauce and colleagues report the results from nine PSAT tags deployed in New Caledonia, recording the world’s deepest known dives for reef manta rays.

All tagged individuals performed dives exceeding 300 m in depth, with a maximum depth of 672 m. Most of the deepest dives occurred during nighttime, possibly to access important food resources. The authors hypothesize that these results may indicate zooplankton abundance in the surface waters surrounding New Caledonian coral reefs is insufficient to sustain reef manta rays. According to the authors, many of the marine protected areas throughout the known range of reef manta rays are coastal and do not extend into deeper offshore waters. As deep-water fisheries increasingly exploit this zone, the study highlights the importance of incorporating offshore waters and deep-water foraging grounds in manta conservation initiatives.

The authors add: Tagged Manta rays (Mobula alfredi) from the never-studied-before population of New Caledonia showed unprecedented deep dive behaviour. More frequent and deeper dives than ever recorded before, Manta rays of New Caledonia set a new depth range to 672 meters.

How manta rays’ injuries heal


This March 2017 video from Australia is called Swimming with Whoopi the Manta Ray.

From the University of Queensland in Australia:

Manta’ rays impressive ability to heal

December 20, 2019

‘Whoopi’ the manta ray — a regular visitor to Western Australia’s Ningaloo Reef — has helped University of Queensland and Murdoch University scientists study rays’ impressive ability to heal.

Whoopi, who has swum with thousands of tourists WA’s over the years, was hit by a boat in 2015, suffering propeller cuts measuring up to 20 centimetres to the edge of her wing.

Dr Christine Dudgeon from UQ’s School of Biomedical Sciences said such a strike was relatively rare, but could cause significant injuries to the animal.

“Manta rays don’t surface to breathe, which you think would reduce their susceptibility to boat strike,” Dr Dudgeon said.

“But these rays, like whale sharks, tiger sharks and other sharks and rays, spend considerable time in surface waters for activities like basking and feeding.

“Most wounds in these species have been attributed to predation, mating attempts and fishing-related injuries or entanglement, but boats do end up hitting some rays — and Whoopi had the cuts to prove it.”

Manta rays and other sharks and rays are considered to have high healing capacity.

“This is likely due, in part at least, to a unique adaptive immune system,” Dr Dudgeon said.

“However, few studies have investigated the rate of wound healing in sharks and rays, and these have mostly focused on the impacts of external and internal tagging procedures, not boat strikes.”

To investigate this phenomenon further, the team compared underwater photographs taken in the Ningaloo Coast World Heritage Area of WA over the past 15 years, and found evidence of greater incidence of boat strike on manta rays than previously thought.

Professor Anthony Richardson from UQ’s Centre for Applications in Natural Resource Mathematics said the results were impressive.

“Whoopi showed us just how fast these beautiful creatures can heal,” he said.

“Her significant wounds had healed by 50 per cent only 46 days after the boat strike, and by day 295 had healed by 95 per cent.”

Dr Dudgeon said the research could be used to inform policy for designing adequate spatial management for the region.

“It’s imperative we reduce the impact of vessels on manta rays and protect their critical habitat,” she said.

“Such management may include speed restrictions during high usage periods, vessel free zones, the use of propeller guards or alternative motors — like jet motors — and public education on vessel-wildlife conflict.”

“Manta rays are incredible healers, but it’s important we keep them safe in the first place.”

Dinosaurs extinct, Italian stingrays survived


This 2011 video is about the fossil fish of Monte Bolca in northeastern Italy.

From the University of Vienna in Austria:

Fossil fish gives new insights into evolution after end-Cretaceous mass extinction

October 2, 2019

An international research team led by Giuseppe Marramà from the Institute of Paleontology of the University of Vienna discovered a new and well-preserved fossil stingray with an exceptional anatomy, which greatly differs from living species. The find provides new insights into the evolution of these animals and sheds light on the recovery of marine ecosystems after the mass extinction occurred 66 million years ago. The study was recently published in the journal Scientific Reports.

Stingrays (Myliobatiformes) are a very diverse group of cartilaginous fishes which are known for their venomous and serrated tail stings, which they use against other predatory fish, and occasionally against humans. These rays have a rounded or wing-like pectoral disc and a long, whip-like tail that carries one or more serrated and venomous stings. The stingrays include the biggest rays of the world like the gigantic manta rays, which can reach a “wingspan” of up to seven meters and a weight of about three tons.

Fossil remains of stingrays are very common, especially their isolated teeth. Complete skeletons, however, exist only from a few extinct species coming from particular fossiliferous sites. Among these, Monte Bolca, in northeastern Italy, is one of the best known. So far, more than 230 species of fishes have been discovered that document a tropical marine coastal environment associated with coral reefs which dates back to about 50 million years ago in the period called Eocene.

This new fossil stingray has a flattened body and a pectoral disc ovoid in shape. What is striking is the absence of sting and the extremely short tail, which is not long as in the other stingrays, and does not protrude posteriorly to the disc. This body plan is not known in any other fossil or living stingray. Since this animal is unique and peculiar, the researchers named the new stingray Lessiniabatis aenigmatica, which means “bizarre ray from Lessinia” (the Italian area where Bolca is located).

More than 70 percent of the organisms, such as dinosaurs, marine reptiles, several mammal groups, numerous birds, fish and invertebrates disappeared during the fifth-largest extinction event in the Earth’s history occurred about 66 million years ago at the end of the Cretaceous. In marine environments, the time after this event is characterized by the emergence and diversification of new species and entire groups of bony and cartilaginous fishes (sharks and rays), which reoccupied the ecological niches left vacant by the extinction’s victims. The new species experimented sometimes new body plans and new ecological strategies.

“From this perspective, the emergence of a new body plan in a 50-million-year-old stingray such as Lessiniabatis aenigmatica is particularly intriguing when viewed in the context of simultaneous, extensive diversification and emergence of new anatomical features within several fish groups, during the recovery of the life after the end-Cretaceous extinction event,” states Giuseppe Marramà.

Reef manta rays, photography helps


This video says about itself:

Reef Manta Rays Dancing Together || ViralHog

Occurred on March 31, 2019 / Oahu, Hawaii, USA

From the University of Queensland in Australia:

Citizen scientists offer ray of hope

July 31, 2019

Volunteer snorkelers and scuba divers have been helping capture images of reef manta rays to better protect the threatened species.

The University of Queensland initiative — Project Manta — relied on these citizen scientists to photograph or video individual reef manta rays (Mobula alfredi) across Australia’s east coast.

UQ PhD candidate Asia Armstrong, who led the study, hopes the data will inform conservation planning and management along the coast.

Manta rays are a great ambassador species for conservation,” Ms Armstrong said.

“Everyone loves them, and they offer a wonderful platform for getting people involved in marine conservation, as people protect what they love.

“With Project Manta, we relied on the cameras and eyes of both trained researchers and volunteers, who helped us build a catalogue of more than 1300 individual reef manta rays, from in excess of 7000 sightings.”

Once images and videos were captured, they were analysed to isolate the distances individual rays were travelling.

“Manta rays have a unique spot pattern on their belly, which allows individuals to be identified from one another,” Ms Armstrong said.

“Each time an animal is photographed we record the date, time and location of the sighting, along with any additional information, like its sex, maturity status, injuries and behaviour.

“When a sighting is matched to an existing record we gain insights into the ray’s movements and population dynamics.”

The researchers were surprised to discover that individual rays had traveled from North Stradbroke Island to the wreck of SS Yongala, just south of Townsville, a distance of more than 1,000 kilometres.

“This is a record-breaking point-to-point movement for a reef manta ray, improving our understanding of the potential home range for this species,” Ms Armstrong said.

“Globally, reef manta rays are listed as vulnerable to extinction, so this information can help inform conservation planning internationally, particularly in regions where this species may be exposed to increased risks and threats.

“It’s important now to connect with regional research groups to enable us to compare catalogues, which may reveal longer distance movements than those we’ve discovered.

“So far, there haven’t been any records of cross-jurisdictional movements of this species — that is, movements between the waters of different countries — which is important to know for conservation planning.

“With the help of international researchers, along with passionate citizen scientists and conservationists, we can really improve the long-term chances for this incredible species.”

Plastic kills sharks, rays


This 2014 video is called The Secret World of Sharks and Rays (Nature Documentary).

From the University of Exeter in England:

Hundreds of sharks and rays tangled in plastic

July 4, 2019

Hundreds of sharks and rays have become tangled in plastic waste in the world’s oceans, new research shows.

University of Exeter scientists scoured existing published studies and Twitter for shark and ray entanglements, and found reports of more than 1,000 entangled individuals.

And they say the true number is likely to be far higher, as few studies have focussed on plastic entanglement among shark[s] and rays.

The study says such entanglement — mostly involving lost or discarded fishing gear — is a “far lesser threat” to sharks and rays than commercial fishing, but the suffering it causes is a major animal welfare concern.

“One example in the study is a shortfin mako shark with fishing rope wrapped tightly around it,” said Kristian Parton, of the Centre for Ecology and Conservation on Exeter’s Penryn Campus in Cornwall.

“The shark had clearly continued growing after becoming entangled, so the rope — which was covered in barnacles — had dug into its skin and damaged its spine.

“Although we don’t think entanglement is a major threat to the future of sharks and rays, it’s important to understand the range of threats facing these species, which are among the most threatened in the oceans.

“Additionally, there’s a real animal welfare issue because entanglements can cause pain, suffering and even death.”

Co-author Professor Brendan Godley, co-ordinator of the university’s marine strategy, added: “Due to the threats of direct over-fishing of sharks and rays, and ‘bycatch‘ (accidental catching while fishing for other species), the issue of entanglement has perhaps gone a little under the radar.

“We set out to remedy this. Our study was the first to use Twitter to gather such data, and our results from the social media site revealed entanglements of species — and in places — not recorded in the academic papers.”

The review of academic papers found reports of 557 sharks and rays entangled in plastic, spanning 34 species in oceans including the Atlantic, Pacific and Indian. Almost 60% of these animals were either lesser spotted dogfish, spotted ratfish or spiny dogfish.

On Twitter, the researchers found 74 entanglement reports involving 559 individual sharks and rays from 26 species including whale sharks, great whites, tiger sharks and basking sharks.

Both data sources suggested “ghost” fishing gear (nets, lines and other equipment lost or abandoned) were by far the most common entangling objects. Other items included strapping bands used in packaging, polythene bags and rubber tyres.

The study identified factors that appear to put certain species more at risk:

  • Habitat — sharks and rays in the open ocean appear more likely to get entangled, as do those living on the sea floor, where materials such as nets loaded with dead fish sink and attract predators, which in turn get stuck.
  • Migration — species that cover long distances appear at more at risk of encountering plastic waste.
  • Body shape — sharks seem to be at greater risk than rays. Species with unusual features — such as manta rays, basking sharks and sawfish — are also at more risk.

Green turtles are more likely to swallow plastic that resembles their natural diet of sea grass, new research suggests: here.

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