Few fast-swimming apex fishes are classified as regional endotherms, or partially warm-blooded, having evolved a relatively uncommon suite of traits (e.g. elevated body temperatures, centralized red muscle, and thick-walled hearts) thought to facilitate a fast, predatory lifestyle. Unlike those apex predators, basking sharks (Cetorhinus maximus) are massive filter-feeding planktivores assumed to have the anatomy and physiology typical of fully ectothermic fishes. New research led by Trinity College Dublin scientists suggests basking sharks are not full ectotherms, instead sharing several traits used to define a regional endotherm, thus deviating from current understanding of the species and questioning the link between physiology and ecology of regionally endothermic shark species.
“The basking shark is a shining example of how little we know about shark species in general,” said Haley Dolton, a Ph.D. candidate at Trinity College Dublin.
“That we still have lots to uncover about the second biggest fish in the world — such a huge, charismatic animal that most people would recognize it — just highlights the challenge facing researchers to gather what they can about species to aid in effective conservation strategies.”
“Regional endotherms are thought to use more energy, and possibly respond differently to ocean warming than other fish species.”
“So lots more work will need to be done to work out how these new findings regarding an endangered species might change previous assumptions about their metabolism or potential distribution shifts during our climate crisis, which is something marine biologists are focusing on as our planet and its seas continue to warm.”
“Hopefully this kind of research will continue the momentum needed to effectively protect these incredible animals in Irish waters and further afield.”
To make the discovery, Dolton and colleagues first undertook dissections of dead basking sharks that washed up in Ireland and…
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