The Secret to a Tuna's sharp turnsBy Kai Sinclair
Bluefin tuna can stretch 3 meters, weigh a metric ton, and reach speeds of 60
kilometers per hour. Yet they still turn on a dime when hunting, thanks in part
to their lymphatic systems. Unlike humans, who use their lymphatic systems to
produce and transport white blood cells, tuna use theirs to move two of their
fins, researchers report today in Science. When scientists dissected the nimble
fish, they discovered empty cavities at the base of their second dorsal and
under-belly fins. These vascular sinuses are connected to a network of vessels
that extend into the fin, between the bones that make up the fins’ rays. When
the team pumped a saline solution into the vascular sinuses of recently
deceased tuna, the solution flowed into the vascular channels and increased
the fins’ internal pressure. This caused the fins to rise and stand erect
from the body. The fish make such changes in their fin position when they
make a series of sharp turns, especially during hunting, the team found.
The researchers suspect that this fin movement offers extra stability during
tuna’s tight maneuvers so the fish don’t have to sacrifice their speed for balance.