Spiny Dogfish Make Cortisol, a Hormone Sharks Were Presumed to Lack
Cortisol is present in the blood of North Pacific spiny dogfish, a team at the University of Manitoba and the Bamfield Marine Sciences Centre reported Oct. 14, 2026, in Proceedings of the Royal Society B. Sharks, rays and skates had been presumed to make none of it.
The paper sets that finding against a narrow presumption rather than a general one. Cortisol, or the closely related corticosterone, regulates energy balance, immune response, salt balance and metabolism across jawed vertebrates. Sharks, rays and skates carry a dominant blood steroid of their own, 1α-hydroxycorticosterone, and since that steroid was identified they have been presumed to produce no cortisol at all. What the dogfish work adds is that cortisol, and the cellular machinery for making it, are there as well.
Alyssa M. Weinrauch, W. Gary Anderson and colleagues found RNA copies of Cyp17, the gene for an enzyme that builds cortisol's chemical precursors, in the dogfish interrenal tissue, the shark's counterpart to the adrenal gland. They record that as the first such confirmation they know of. Cortisol then turned up in the blood after two separate treatments: 48 hours of recovery from diluted seawater at 21 parts per thousand and a 5-day course of antibiotics.
To test what the hormone does there, the team implanted cortisol at levels a dogfish would normally carry. Blood sugar stayed persistently low, while the salts and other dissolved substances in the blood barely moved. The authors report that the hormone acted on blood sugar at that level, and say definitive roles for it remain unclear.
Weinrauch and colleagues also report that their results support a new hypothesis, that microbes take part in building these steroids in sharks and their relatives. The paper is open access under a CC BY license.
