Page 36 - AlertDiver_Winter2013

34 | WINTER 2013
T e x t a n d P h o t o s B y E t h a n D a n i e l s
Reefs of Poison
and Venom
Put modestly, the underwater
world is diverse. It harbors
plant and animal life that runs
the gamut from single-celled
microorganisms to complex, 90-foot-long
vertebrates that feed on prey they can’t
see. Marine organisms have descended in
continuous lineages that go back 3 billion
years, and over that extraordinary period
countless species have appeared and then,
for one reason or another, petered out,
disappearing into oblivion.
The creatures divers observe on today’s
coral reefs have sprung from unseen
ancestors, many of which we know absolutely
nothing about. From sponges to anemonefish,
the inhabitants of modern reefs and other
marine ecosystems have been selected over
many generations. Some organisms are better
suited to certain environments, are more
capable of acquiring food or have the means
to protect themselves just a bit better than
others. While underwater, divers observe
evolutionary winners in the habitats for which
they have been honed.
A Dangerous Place
The ostensible harmony of the marine
ecosystems divers enjoy is an utter ruse.
From the perspective of any invertebrate
or fish, the reef is a ruthless place where
competition is fierce, and one can disappear
down a gullet in the blink of an eye.
Evolutionary pressures come from both
the physical environment and from other
organisms: predators, prey, competitors and
even those linked by mutually beneficial
symbiosis. Today’s coral reefs are chock-full
of creatures coexisting in a balance that is
subtle and built around interdependence and
coevolution.
So how did today’s worms, bryozoans,
echinoderms, tunicates and fishes “win”?
How do sluggish nudibranchs and inert
corals outcompete other animals that would
take their place if they could? Virtually
every part of a creature contributes to its
success, and due to a variety of ecological
factors, tropical-reef animals have become
particularly specialized over many
generations, adapting to precise habitats,
food types, salinities and other variables.
Among the strategies adopted over geologic
time (which include speed, strength and
size), one of the most effective is the
production of potent chemicals that help
determine which species are victorious and
which are left by the evolutionary wayside.
Enter the Toxin
Over hundreds of millions of years, plants
and animals in reef ecosystems have
fashioned toxins through random genetic
mutations and natural selection. These
chemical compounds are used in defensive
and predatory tactics including scrambling
adversaries’ brain signals, paralyzing muscles,
destroying blood cells and digesting tissues
from within. The “tranquil” reefs we divers
see are anything but.
It may be strange to consider while drifting
over the lively activity of a healthy reef, but
Chemical warfare in evolutionary arms races
LIFE AQUATIC