An unusual hunt kicked off in March when scientists were eager to retrieve a runaway corpse. It belonged to a Greenland shark, a very rare find for beachcombers but one that senior research fellow Professor Rosie Woodroffe stumbled across in Cornwall, UK.
However, the Greenland shark got the heck out of dodge when the tide came in and so a search party was launched to try and retrieve the dead animal and the academic insights its body would contain. As elusive creatures that can live 2,600 meters (8,530 feet) deep and are the world's longest-living vertebrates, they can be hard to study. Thankfully, just a few days later it was scooped out of the ocean.
The Greenland shark has since been under the care of the Cornwall Marine Pathology Team, part of the Zoological Society London's (ZSL) Cetacean Stranding Investigate Programme (CSIP). Among them was pathologist James Barnett, who noticed something was a bit off with the shark’s brain.
What’s that I hear you say? You’ve never seen a Greenland shark brain? Let’s change that.
“During the post-mortem examination, the brain did look slightly discoloured and congested and the fluid around the brain was cloudy, raising the possibility of infection,” Barnett said in a statement emailed to IFLScience. It seems the Greenland shark had developed meningitis: an infection of the protective membranes that surround the brain and spinal cord, which affects humans too and can be deadly.
Brain matter is a very delicate and soft tissue that can quickly degrade if not preserved properly (though scientists did once find a 2,600-year-old human brain). As such, brains like this shark’s are usually fixed with formaldehyde during research to help keep things from getting too mushy.
Firmer formaldehyde brain in hand, Barnett’s team was able to solidify their conclusions.
“[The infection] was then confirmed on microscopic examination of the brain (histopathology),” he said. “A species of Pasteurella, a bacteria, was isolated from the fluid and this may well have been the cause of the meningitis.”
The juvenile female shark, estimated to be around 100 years old (they can live up to 400 years), was far from her natural habitat when she died. It’s likely the meningitis is to blame for this, and the silt found in her stomach indicates it's likely she was still alive when she stranded.
The untimely end for Earth’s longest-living vertebrate marks the first time meningitis has been diagnosed in a Greenland shark, and it’s hoped that further insights will be uncovered with closer inspection of the animal’s remains.
“The remains of the shark will be going to the Natural History Museum, London and various samples are going to collaborating researchers so they can gain as much information as possible from this rare stranding,” Barnett told IFLScience.
Avenues of investigation include its skin, which may hold clues to the evolution of hydrodynamic flow in sharks, a toxicology screen of its liver to detect any pollutants in its system, and microplastic and dietary analysis of its gastrointestinal tract.
It’s also hoped that its true age can be identified through stable isotope analyses of its eye lens and vertebrae. “Was it swimming around the deep when the first world war was raging?” asked Barnett.
A few samples (frozen to a chilly -80°C/176°F) will join the Sanger Institute’s Tree of Life Project for genome sequencing, marking its first Greenland shark entry. That’s a lot of insight from just one animal.
“Huge thanks are owed to the volunteers of Cornwall Wildlife Trust Marine Strandings Network and all those who spotted and brought the body to shore,” said CSIP project lead Rob Deaville.
“This was an exceptional collaborative effort by all involved and was a unique opportunity to learn more about the life of this cryptic and endangered deep-water shark.”