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"Stories from the Sea"
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"Urchin Odyssey: Sex Among Plankton"
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I must look rather strange to you,
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all covered in spines,
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without even a face.
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But I've taken many forms during my life.
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I started out just like you,
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a tiny egg in a watery world.
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My parents never knew each other.
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One moonlit night before a storm,
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thousands of urchins, clams and corals
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released trillions of sperm and eggs into the open sea.
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My father's sperm somehow met my mother's egg,
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Instantly, I became an embryo the size of a speck of dust.
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After a few hours of drifting,
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I cleaved in two, then four,
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then eight cells. Then so many I lost count.
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In less than a day,
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I developed a gut and a skeleton.
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I became a rocket ship,
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a pluteus larva.
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I floated through the world of plankton,
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searching for tiny algae to eat.
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I was surrounded by all kinds of organisms,
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larvae of all sorts.
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Most are so different from their adult form
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that biologists have a tough time figuring out who they are.
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Try matching these youngsters to their parents.
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This veliger larva
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will turn into a snail.
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This zoea, into a crab.
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And this planula into a [unclear] jelly.
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Some of my young companions are easier to picture as grown-ups.
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These baby jellies, know as [unclear]
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already resemble their beautiful but deadly parents.
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Here in the plankton,
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there's more than one way to get your genes into the next generation.
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Most medusa jellies
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make special structures called polyps
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that simply bud off babies with no need for sex.
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Salps are similar.
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When food is abundant, they just clone themselves into long chains.
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