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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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and they fused.
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Fertilization.
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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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For weeks,
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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 cnidaria jelly.
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Some of my young companions are easier to picture as grown-ups.
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These baby jellies, known as ephyrae
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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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A plankton is full of surprises when it comes to sex.
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Meet the hermaphrodites.
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These comb jellies and arrow worms
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produce, store and release both sperm and eggs.
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They can fertilize themselves
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or another.
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When you're floating in a vast sea,
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with little control over who you may meet,
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it can pay to play both sides of the field.
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The majority of species here, however,
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never mate, nor form any sort of lasting bonds.
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That was my parents' strategy.
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There were so many of us pluteus larvae,
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I just hid in the crowd while most of my kin were devoured.
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Not all parents leave the survival of their offspring to chance.
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Some have far fewer young,
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and take much better care of them,
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brooding their precious cargo for days, even months.
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This speedy copepod
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totes her beautifully packaged eggs for days.
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This phronima crustacean carries her babies on her chest,
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then carefully places them in a gelatinous barrel.
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But the black-eyed squid takes the prize.
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She cradles her eggs in long arms for nine months,
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the same time it takes to gestate a human infant.
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Eventually all youngsters have to make it on their own in this drifting world.
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Some will spend their whole lives in the plankton,
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but others, like me, move on.
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A few weeks after I was conceived,
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I decided to settle down
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and metamorphosed into a recognizable urchin.
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So now you know a bit of my story.
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I may just be a slow-moving ball of spines,
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but don't let my calm adult exterior fool you.
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I was a rocket ship.
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I was a wild child.