How Life Begins in the Deep Ocean - Tierney Thys

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Where do squid, jellyfish and other sea creatures begin life? The story of a sea urchin reveals a stunningly beautiful saga of fertilization, development and growth in the ocean depths.

Lesson by Tierney Thys, visualization by Christian Sardet (CNRS/Tara Oceans), Noé Sardet, and Sharif Mirshak (Plankton Chronicles Project, Parafilms).

I must look rather strange to you,

all covered in spines,

without even a face.

But I've taken many forms during my life.

I started out just like you:

a tiny egg in a watery world.

My parents never knew each other.

One moonlit night before a storm,

thousands of urchins, clams and corals

released trillions of sperm and eggs
into the open sea.

My father's sperm
somehow met my mother's egg,

and they fused.

Fertilization.

Instantly, I became an embryo
the size of a speck of dust.

After a few hours of drifting,

I cleaved in two,

then four,

then eight cells.

Then so many, I lost count.

In less than a day,

I developed a gut and a skeleton.

I became a rocket ship,

a pluteus larva.

I floated through the world of plankton,

searching for tiny algae to eat.

For weeks, I was surrounded
by all kinds of organisms,

larvae of all sorts.

Most are so different
from their adult form

that biologists have a tough time
figuring out who they are.

Try matching these youngsters
to their parents.

This veliger larvae
will turn into a snail;

this zoea, into a crab;

and this planula, into a clytia jelly.

Some of my young companions
are easier to picture as grown-ups.

These baby jellies, known as ephyrae,

already resemble their beautiful
but deadly parents.

Here in the plankton,
there's more than one way

to get your genes
into the next generation.

Most Medusa jellies make
special structures called polyps,

that simply bud off babies
with no need for sex.

Salps are similar.

When food is abundant,

they just clone themselves
into long chains.

The plankton is full of surprises
when it comes to sex.

Meet the hermaphrodites.

These comb jellies and arrow worms

produce, store and release
both sperm and eggs.

They can fertilize themselves,

or another.

When you're floating in a vast sea,

with little control over who you may meet,

it can pay to play
both sides of the field.

The majority of species here,
however, never mate,

nor form any sort of lasting bonds.

That was my parents' strategy.

There were so many of us pluteus larvae,

I just hid in the crowd,

while most of my kin were devoured.

Not all parents leave
the survival of their offspring to chance.

Some have far fewer young
and take much better care of them,

brooding their precious cargo
for days, even months.

This speedy copepod

totes her beautifully
packaged eggs for days.

This Phronima crustacean
carries her babies on her chest,

then carefully places them
in a gelatinous barrel.

But the black-eyed squid takes the prize.

She cradles her eggs
in long arms for nine months,

the same time it takes
to gestate a human infant.

Eventually, all youngsters
have to make it on their own

in this drifting world.

Some will spend
their whole lives in the plankton,

but others, like me, move on.

A few weeks after I was conceived,

I decided to settle down,

and metamorphosed
into a recognizable urchin.

So now you know a bit of my story.

I may just be a slow-moving
ball of spines,

but don't let my calm
adult exterior fool you.

I was a rocket ship.

I was a wild child.