Southwest Fisheries Science Center Biologist
Nick wegner holds captured opah.
Deep-water fish called opah appear to be the
first fully warm-blooded fish species ever
discovered, according to a new paper published
in Science. Researchers say the unique biology
behind opah, also known as moonfish, allow the
species to operate at peak performance even
within frigid ocean depths.
Being warm-blooded has its perks. Birds and
mammals (or endotherms) conserve their
internal heat to maintain high body
temperatures, which helps them flee predators,
chase prey and thrive in sub-zero climates. But
fish—and other cold-blooded animals, like
reptiles and amphibians—aren’t so lucky. Most
deep-sea fish move slowly, preferring to
ambush prey rather than give chase, as their
low body temperatures (and reaction speeds)
mirror the cool ocean water. But now, scientists
say they have discovered one exception to this
rule: opah.
“It’s a real advantage if you’re in this deep, cold
habitat and you’re swimming around with a
warm body,” says Nick Wegner, an NOAA
fisheries biologist and lead author on the paper.
“It increases the rates of all the reactions that
occur within the body—you can swim faster, see
better, react faster and capture cold-bodied
prey that are not able to respond nearly as
quickly.”
Opah, which resemble large, colorful tires,
thrive in the deep sea and are an increasingly
popular seafood. Although Wegner had been
studying opah for years, he recently noticed that
warm blood vessels leaving the fish’s heart
wrap around cooler blood vessels returning
from its gills. Later, he determined that
opah generate heat by flapping their pectoral
fins, and retain that heat through this dense
layer of blood vessels. Opah’s internal heating
system is capable of keeping the fish’s heart and
brain at peak performance, even at depths of
up to 1,300 feet.
Certain tuna and shark species also retain body
heat, and warm select muscles for high-
performance hunting, but these species are far
from warm-blooded: Most of a shark or tuna’s
body (including its heart and other vital organs)
remains cold. “Opah is the first fish that can
circulate warm blood throughout the entire
body, and that gives it some advantages over
tuna and shark species,” Wegner says. “Since
they can keep their entire bodies warm, they
can stay down deep, continuously close to their
forage base.”


Source- www.vocativ.com/news/192800/moonfish-opah-first-warm-blooded-fish/?

news.nationalgeographic.com/news/2015/02/150205-opah-fish-sushi-ocean-animals-science/