The world’s longest-living vertebrate is the Greenland shark – the fact they can live up to 500 years is said to be believable because they live in freezing cold water and thus have a slow metabolism. You can imagine the surprise of some researchers, then, when they found a suspected Greenland shark (Somniosus microcephalus) casually cruising around a coral reef off Belize.
The bizarre sighting marks the first time a sleeper shark (the family in which Greenland sharks sit) has ever been recorded in the western Caribbean. It was discovered by researchers from Florida International University’s Predator Ecology and Conservation Lab while working with local fishers to tag tiger sharks.
“At first, I was sure it was something else, like a six gill shark that are well known from deep waters off coral reefs,” said PhD candidate Devanshi Kasana from FIU in a statement, who was lead author on a paper about the discovery published in Marine Biology. “I knew it was something unusual and so did the fishers, who hadn’t ever seen anything quite like it in all their combined years of fishing.”
A six gill shark would’ve been an exciting find in itself, being enormous and more commonly found at depths of 2,000 meters (6,500 feet). However, Kasana’s PhD advisor and Director of Sharks & Rays Conservation Research at Mote Marine Laboratory & Aquarium suspected she had something even more unusual on the line: a Greenland shark.
Experts later confirmed that the mysterious animal definitely sat within the sleeper shark family, though an exact species couldn’t be determined for certain. However, being so large (between 3 and 3.5 meters (9.8 and 11.5 feet)) led the researchers to suspect it could’ve been either a Greenland shark or a hybrid with another large species such as the Pacific sleeper (Somniosus pacificus).
An ectoparasitic copepod (a type of crustacean) in the giant shark’s eye was another clue. Ommatokoita elongate, a 30 millimeter (1.2 inch) long pinkish-white parasite, is a big fan of the corneas of Greenland sharks and is commonly found permanently fused to them. Nasty for Greenland sharks, but sometimes handy for researchers trying to identify them.
A live sighting of such an animal is an exciting one indeed, as demonstrated by the fanfare surrounding the body of a deceased Greenland shark earlier this year. We rarely get an opportunity to study these enormous animals up-close (though we do have a video of their heart beating ex situ) which could reveal insights into their absurd longevity – so when a carcass that had been identified got swept back out to sea, a chase ensued.
The animal’s body was victoriously retrieved and donated to science, and was diagnosed with the first-ever recorded case of meningitis in a Greenland shark.
As for their living Greenland shark (or perhaps Greenland-Pacific-sleeper hybrid, as the researchers speculate), the researchers are proud that in collaborating with the fishers in Belize they were able to record this chance encounter.
“Great discoveries and conservation can happen when fisherman, scientists and the government work together,” said Beverly Wade, Director of the Blue Bond and Finance Permanence Unit in the Office of the Prime Minister of Belize, in a statement.
“We can really enhance what we can do individually, while also doing some great conservation work and making fantastic discoveries, like this one.”
