Warm-blooded Sharks More Common Than Thought

Sharks that are warm-blooded such as the Great White and extinct Megalodon could be much more common than thought.

But the discovery rings alarm bells for marine biologists as a changing climate could make it harder for warm-blooded fish to live.

The smalltooth sand tiger, thought to have diverged from the Meg at least 20 million years ago, has been found to have anatomic features that suggest it is warm-blooded or has regional endothermy.

This comes soon after the similar shock that slow-moving, filter-feeding basking sharks are also warm-blooded.

Some of the most famous sharks, like the white shark or the extinct megalodon, were thought to be unusual in being among the less than one percent of warm-blooded shark species.

However, researchers now believe there are more warm-blooded sharks than science thought, and that this warm-bloodedness evolved a long time ago.

Senior author Dr. Nicholas Payne said: “We think this is an important finding, because if sand tiger sharks have regional endothermy then it’s likely there are several other sharks out there that are also warm-bodied.

“We used to think regional endothermy was confined to apex predators like the Great White and extinct Megalodon, but now we have evidence that deep water ‘bottom-dwelling’ sand tigers, and plankton-eating basking sharks also are warm bodied.

“This raises plenty of new questions as to why regional endothermy evolved, but it might also have important conservation implications.”

The research, by Trinity College Dublin and published in the journal Biology Letters, was discovered by dissecting dead smalltooth sand tiger sharks that washed up in Ireland and the UK.

These new findings have taken marine biologists millions of years back in time as they look to the future with concern.

Based on the demise of the Megalodon shark they believe other warm-blooded sharks may be at great risk from warming seas.

Lead author Dr. Haley Dolton said: “Our understanding of science continually grows and it’s becoming clear that whenever regional endothermy evolved in the past it has been retained in a growing number of shark species with very different lifestyles.

“When we first realized that the smalltooth tigers have traits associated with regional endotherms I thought ‘here we go again!’, but the next time we see it in another species I might be a little less shocked.

“The discovery itself is very interesting for a marine biologist, but it also has major implications from a conservation perspective for regional endotherms.

“We believe changing environments in the deep past was a major contributor to the megalodon’s extinction, as we think it could no longer meet the energetic demands of being a large regional endotherm.

“We know the seas are warming at alarming rates again now and the smalltooth tiger that washed up in Ireland was the first one seen in these waters. That implies its range has shifted, potentially due to warming waters, so a few alarm bells are ringing.”

Produced in association with SWNS Talker