A stranded Greenland shark found off Cornwall has died of meningitis, according to an autopsy, providing what is thought to be the first evidence of the disease in the species.
The 4m long shark, around 100 years old, was first spotted by a dog walker on March 13 on a beach near Penzance but was washed back into the sea before it could be properly examined . After a two-day search he was discovered floating in the water off Newlyn Harbor beach by a tourist boat and an autopsy was carried out.
Greenland sharks live up to 2,600 meters below the surface of the Arctic and North Atlantic oceans. Pathologists believe meningitis explains why this female was out of her natural deep-sea habitat. His brain was slightly discolored and congested with cloudy fluid, which contained a type of bacteria called Pastoral, likely to have caused meningitis. It is not known how the shark contracted the infection.
The last time a Greenland shark was stranded in the UK was in Northumberland in 2013. The discovery of this specimen gave researchers the opportunity to study the vertebrate species with the longest lifespan of the planet – some are said to be over 400 years old. Although it was probably born just after the First World War, this shark was still considered a juvenile. Females are thought to reach maturity at 150 years old, when they are about 4.2 meters long.
“This unfortunate and extraordinary stranding has given us insight into the life and death of a species we know little about,” said Rob Deaville of the Cetacean Strandings Survey Program (CSIP) of the Zoological Society of London (ZSL). “It’s almost certainly the oldest animal I’ve ever seen.
“With only a small handful of previously recorded Greenland shark strandings in the UK, this probably represents the first necropsy ever carried out on this species in this country and was a unique opportunity to learn more about the life and the death of this cryptic and endangered deep-water shark,” he said.
Meningitis is caused by a viral or bacterial infection. The same Pastoral bacterium has been found to cause meningitis in humans, but it is extremely rare. Pathologists do not yet know which species of Pastoral affected the shark and will investigate further. Meningitis has been previously described in sharks, but it’s unclear how widespread it is, Deaville said. He’s seen a few stranded basking sharks affected over the past decade, and it’s also been reported in captive lemon sharks.
The autopsy was carried out by the Cornwall Marine Pathology Team, part of CSIP. Pathologists began with an external examination to look for a possible cause of death, such as fillet marks or parasites. Then they opened the body to access the organs, examining each for signs of abnormalities. Samples were collected, documented and sent for detailed analysis, such as diet, exposure to pollution and disease.
Pathologist James Barnett, who carried out the autopsy with a team of volunteers, said: “The shark’s body was in poor condition and there were signs of haemorrhage in the soft tissue around the pectoral fins which, coupled with the slime found in her stomach, suggested she may well have failed live.
“As far as we know, this is one of the first post-mortem examinations here in the UK of a Greenland shark and the first report of meningitis in this species.”
The shark was dissected and body parts sent to research institutes across the country for examination.
Research on its skin will examine the evolution of how sharks swim. Its gastrointestinal tract will reveal if there are any microplastics present, and scientists will examine other hard remains such as fish ear bones or squid beaks, which could shed light on the shark’s diet. Toxicology tests on its liver could reveal what pollutants the shark has been exposed to over its long life.
Some samples, stored at -80°C, are being sent to the Sanger Institute to sequence the whole genome as part of the Darwin Tree of Life project, where they could inform research on cancer and aging.
Greenland sharks are the only species of shark hardy enough to spend all year in the Arctic Ocean. Their very slow metabolism means they are well adapted to cold water, and may also explain their long lifespan. They grow less than 1 cm per year, have a top speed of just 2.9 km/h and a heart that beats five or six times per minute. The largest specimen ever found was a 5 meter female between 272 and 512 years old.
“I’ve been doing this job for 25 years and we get a lot of strandings, but I certainly wasn’t expecting a call about a shark from Greenland on a Sunday afternoon – we were a bit stunned,” Deaville said. “There are so many weird and wonderful things about them.”
Greenland sharks were once hunted for their liver oil, but now many end up caught in fishing nets. The species is classified as vulnerable. CSIP has performed autopsies on 4,500 cetaceans over 30 years, making it one of the world’s largest databases of strandings and causes of death.
The stranded shark was spotted by Rosie Woodroffe, a ZSL biologist, who was walking her dog. “I immediately thought it looked like a Greenland shark but, not being a shark expert, I assumed I must be wrong and reported it to the Marine Strandings Network as a shark. presumed pilgrim.”
When she got home, she dug up a book about sharks and realized what she had found. “I can’t stop thinking about this shark from Greenland, found dead in the sea tonight” she then wrote on Twitter. “Even though she was ‘just’ a little over 100 years old, she shared the Earth with thylacines and passenger pigeons. She calmly swam in the deep ocean as wars raged above from her.
CSIP urges anyone who spots a stranding to call the national helpline number on 0800 652 0333. A research paper examining the shark’s post-mortem investigations will be released.