Biology Reference
In-Depth Information
John McCosker helping the great white shark in Steinhart's Round-
about. (Photo courtesy Al Giddings Images)
One observation I made during that long night was that the “look”
of the shark just wasn't right. Although hard to describe, something
was missing. Its eyes had the blank look of someone in a trance, with
their eyes open but not really seeing. Since that day I've seen that look
in the eyes of other sharks and have concluded that the brain behind
those eyes was no longer functioning. The nerves and muscles involved
in swimming and breathing continued to work, at least to some de-
gree, but the animal was swimming dead. At that point there was prob-
ably no way to repair the damage done and bring the shark back to
life. In spite of our wishes for its recovery, we were wasting our time
going through those cold, numbing motions again and again.
White sharks are considered “ram” ventilators: they need to swim in
order to force oxygenated water across their gills. A period of non-
swimming can result in a critical lack of oxygen to the brain, leading
to damage and the eventual death of that organ. Without a fully func-
tioning central nervous system, these animals can never survive. Pre-
cisely how long an immobilized shark can survive without oxygen is
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