Australia's Great Barrier Reef
In the liquid skin of planet Earth live creatures of unearthly beauty.
These tiny animals have crossed oceans of space
and time in an epic bid for survival.
Wanderers through inner space,
they carry the future of their species.
On their odyssey
they have faced extinction and awesome planetary force.
Theirs is an evolutionary success story,
made possible by a remarkable reproductive strategy.
Reefs are exotic interruptions in otherwise barren tropical seas.
They're oases of life, vibrant, colorful and competitive.
But this vast canvas of living art
has not just materialized out of the blue.
Coral and its cohorts have arrived from somewhere.
Though they seem solid and unmoving,
reefs have spread themselves throughout the tropical oceans.
How have they overcome their immobility?
The answer has its origin
in one of life's most fundamental acts - sex.
But the reproductive rites of
coral communities are shrouded in mystery.
It's only in the last ten years
that the reef has begun to reveal its private life.
For animals sex is a fact of life,
but for the 'rocks' of the reef
a sex life would seem out of the question.
But corals are not rocks, they're colonies of tiny animals.
Only the outer surface of these colonies is alive;
a living skin populated by polyps.
Their structure is simple,
a tube with a mouth surrounded by stinging tentacles.
These tiny animals a few millimeters across build reefs
The beauty of the individual rivals that of the colony as a whole.
A single pioneering polyp clones
or buds itself endlessly to produce a colony of hundreds,
even thousands, of identical individuals.
In theory a polyp could live forever this way,
unchanging and unmoving.
But change and mobility are essential to all species.
On the reef sex achieves both in one elegantly simple solution.
It's a brief extravaganza, cued by the summer moon,
and for the rest of the year
the priority is coping with life's demands.
Inside the reff's barrier, garden eels vie for tasty morsels.
They inspect drifting particles.
Some are food,
some just broken parts of other reef creatures,
but in the quiet lagoon every particle is inspected by somebody.
A goatfish snuffles industriously.
Within a self-made sandstorm it feasts on small worms
and mollusks which it locates using sensitive barbells.
But the real heavy mover in the sand business are sea cucumbers.
The basic design is a long hollow tube
that creeps around the lagoon floor.
They push sand in one end... and out the other.
Some sea cucumbers mop the reef with sticky feet,
passing edible particles into their mouths.
Nature constantly tests and refines its designs
the basic theme remains, only the detail varies.
With its body completely buried in sand another sea cucumber unfurls
its feathery arms to net drifting debris.
Every particle of sand in the lagoon was once part of the animals
and plants that make up the reef.
Sand production is aided by heavy-jawed grazers
like the bumphead parrotfish.
Moving in herds like buffalo over the reef
they bite off pieces of coral,
crush it to powder and
leave clouds of new sand in their wake.
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