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posted by hubie on Thursday May 18 2023, @10:34PM   Printer-friendly
from the breathe-deep-the-gathering-gloom dept.

Hammerhead sharks found to hold their breath on deep water hunts to stay warm:

Scalloped hammerhead sharks hold their breath to keep their bodies warm during deep dives into cold water where they hunt prey such as deep sea squids. This discovery, published in Science by University of Hawai'i at Mānoa researchers, provides important new insights into the physiology and ecology of a species that serves as an important link between the deep and shallow water habitats.

"This was a complete surprise," said Mark Royer, lead author and researcher with the Shark Research Group at the Hawai'i Institute of Marine Biology (HIMB) in the UH Mānoa School of Ocean and Earth Science and Technology. "It was unexpected for sharks to hold their breath to hunt like a diving marine mammal. It is an extraordinary behavior from an incredible animal."

Shark gills are natural radiators that would rapidly cool the blood, muscles, and organs if scalloped hammerhead sharks did not close their gill slits during deep dives into cold water. These sharks are warm water animals but feed at depths where seawater temperatures are similar to those found in Kodiak Alaska (around 5ºC/ 40ºF), yet they need to keep their bodies warm in order to hunt effectively.

"Although it is obvious that air-breathing marine mammals hold their breath while diving, we did not expect to see sharks exhibiting similar behavior," said Royer. "This previously unobserved behavior reveals that scalloped hammerhead sharks have feeding strategies that are broadly similar to those of some marine mammals, like pilot whales. Both have evolved to exploit deep dwelling prey and do so by holding their breath to access these physically challenging environments for short periods."

[...] "This discovery fundamentally advances our understanding of how scalloped hammerhead sharks are able to dive to great depths and withstand frigid temperatures in order to capture prey," said Royer. "It also demonstrates the delicate physiological balance that scalloped hammerhead sharks must strike in order to forage successfully."

[...] "This extraordinary physiological feat that allows scalloped hammerhead sharks to expand their ecological niche into the deep sea could very well make them vulnerable to additional human impacts."

Journal Reference:
Mark Royer et al., "Breath holding" as a thermoregulation strategy in the scalloped hammerhead, Science (2023). DOI: 10.1126/science.add4445.


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  • (Score: 4, Interesting) by hendrikboom on Friday May 19 2023, @02:49AM (3 children)

    by hendrikboom (1125) Subscriber Badge on Friday May 19 2023, @02:49AM (#1306948) Homepage Journal

    Sharks are already pretty weird.

    I heard they are fresh-water fish that went back into the ocean.

    And instead of getting rid of the chemical pumps that allow fresh-water fish to retain their body salt without absorbing oodles of water by osmosis,
    the sharks acquired another chemical pump to compensate for the environmental salt.

    And then ... there are fresh-water sharks.

    • (Score: 0) by Anonymous Coward on Friday May 19 2023, @06:32AM (1 child)

      by Anonymous Coward on Friday May 19 2023, @06:32AM (#1306959)
      Citation for that? What I know is sharks retain urea but I don't see anything that says that sharks descended from a lineage that went to freshwater and back
    • (Score: 1) by shrewdsheep on Friday May 19 2023, @10:05AM

      by shrewdsheep (5215) on Friday May 19 2023, @10:05AM (#1306977)

      And instead of getting rid of the chemical pumps that allow fresh-water fish to retain their body salt without absorbing oodles of water by osmosis,
      the sharks acquired another chemical pump to compensate for the environmental salt.

      This is what all organisms do. I surmise shark cells have the same (or very similar) ion composition to humans. Salt concentrations within our body are still what they were in the primordial ocean, thereby being a bit less salty than today's oceans. Whichever environment organisms (at least animals) specialized into, they took that composition with them. It seems to be very sensitive to change.

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