Page 10 - 2006 DT 12 Issues

Beating the Odds larity to ancient progenitors. They survived so long.
display many features that are clearly Ecologist Steven Austad of the
orseshoe crabs are among primitive. No one can say how ani- University of Idaho says, “Sheer luck
earth’s oldest creatures. Not mals functioned millions of years ago, is a major consideration” in determin-
Hreally crabs at all, they are however, these “fossils” are definitely dif- ing survival. It might be no more than

closely related to scorpions, ticks and ferent from other species of their kind. accidentally dodging a lethal “bullet”
land spiders. For at least 300 million Living fossils are usually found that hits a non-vital spot on one’s DNA;
years, these slow-moving aquatic at the end of very long branches in the having no significant predators; or not
animals have gone about their busi- tree of life. “What is significant is that being in the wrong place at the wrong
ness virtually unchanged. Their fossils the lineage to which they belong is time, avoiding extinction.
have been found in 360 million-year- isolated phylogenetically,” says evo- Luck aside, many animals and
old sediments looking much the same lutionary biologist David Wake of the organisms exhibit defensive strategies
as they do today. Considered “living University of California at Berkeley. that have stood the test of time. Mil-
fossils,” they are close relatives of “This means they have no close or very lipedes have many forms of defense.
the now extinct primitive arthropods close relatives.” One species with an exoskeleton coils
known as trilobites, and evolved up its segmented body to repel attacks.
in the same warm shallow seas An ancient species, possibly the oldest,
of the Paleozoic Era. Why have uses barbed grappling hooks to fend
they survived so long? off hungry ants.
Scientists generally agree Some animals use chemicals or
that 99.9 percent of all species noxious, irritating fluids for defense.
that have inhabited the planet The Gila monster, found in the South-
have gone extinct. Yet there are west (there’s reportedly one in Red
a surprising number of plants, Rock Canyon), is at least 30 million
animals, insects and other or- years old. One of only two species
ganisms that have beaten the of venomous lizards in the world, its
odds. How do they do it? No crushing bite delivers a neurotoxin
one is really sure, but the ability that, while not lethal to humans, is
to adapt is one obvious element extremely painful. This shy, slow-mov-
in survival. ing but surprisingly agile lizard is not
Deep in the ocean’s eternal especially aggressive, but its defense
darkness, scientists have discovered strategies have been highly effective.
primitive animals whose ancestors Gila monster A long lived species may be high-
have been swimming in saltwater ly adaptable, have a range of defenses,
caves for millions of years. or be able to compensate but still die
They have lost their eyes and pigment, One example he cites is the tailed off from a simple infection. “These
now unnecessary in their present en- frog, which is at the end of a branch things that seem to have lasted so long
vironment. One tiny species, called that split off 150 million-years-ago. must have been protected against dis-
Remipedia, may have existed since the The species uses a more energy saving ease,” says Steven Austad. “They must
days of the dinosaurs. While it looks hunting technique than other frogs. Its have good cellular level defenses.”
like a centipede, its nearest relatives tail is also the male’s sex organ which The most celebrated of living
are known only from fossils that may it uses to fertilize females internally, fossils is a fish called a coelacanth,
date back 50 million years or more. rather than externally after the eggs the oldest representative of living fish
A commonality among living are disgorged. These details may or known to date. Thought to be extinct
fossils is not just their physical simi- may not be clues to why the frog has until it was rediscovered in 1938, this

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