How does a jellyfish sting? - Neosha S Kashef

You're swimming in the ocean
when something brushes your leg.

When the tingling sets in,

you realize you've been stung
by a jellyfish.

How do these beautiful, gelatinous
creatures pack such a painful punch?

Jellyfish are soft
because they are 95% water

and are mostly made of a translucent
gel-like substance called mesoglea.

With such delicate bodies,

they rely on thousands of venom-containing
stinging cells called cnidocytes

for protection and prey capture.

Even baby jellyfish,
the size of a pencil eraser,

have the ability to sting.

Larval jellyfish, ephyrae, look like
tiny flowers pulsating in the sea.

As they grow, they become umbrella-shaped
with a bell at the top

and descending tentacles
around the margin.

The largest species of jellyfish,
the lion's mane,

has tentacles that can extend
more than 100 feet,

longer than a blue whale.

These tentacles contain
most of the stinging cells,

although some species have them
on their bells, too.

Venom is ejected via a nematocyst,

a whip-like hollow tubule,

which lies coiled under
high osmotic pressure.

When mechanical or chemical stimuli
activate an external trigger,

the lid of the cell pops open
and sea water rushes in.

This forces a microscopic barbed
harpoon to shoot out,

penetrate and inject
venom into its victim.

Nematocyst discharge can occur
in less than a millionth of a second,

making it one of nature's fastest
biomechanical processes.

Nematocysts can continue
to fire even after a jellyfish has died,

so it's important to remove
lingering tentacles stuck to the skin.

Rinsing with vinegar will usually render
undischarged nematocysts inactive.

Seawater can also help
remove residual nematocysts.

But don't use fresh water
because any change in salt balance

alters the osmotic pressure
outside of the cnidocyte

and will trigger the nematocyst to fire.

That's why urinating on the affected area,
a common folk remedy,

may do more harm that good,
depending on the composition of the urine.

Most jellyfish stings
are a painful nuisance,

but some can be deadly.

An Indo-Pacific box jelly,
also called a sea wasp,

releases venom which can cause
contraction of the heart muscles

and rapid death in large doses.

There's an anti-venom,
but the venom is fast-acting,

so you'd need immediate
medical intervention.

Despite the impressive power
in their tentacles,

jellies aren't invincible.

Their stinging cells are no match
for the armor of thick-skin predators,

like the leatherback turtle
and ocean sunfish.

These predators both have adaptations
that prevents slippery jellyfish

from escaping after they are engulfed:

backwards pointing spines
in the turtle's mouth and esophagus

and recurved teeth
behind the sunfish's cheeks.

Even tiny lobster slipper larvae
can cling to the bell of a jellyfish

and hitch a ride,

snacking on the jelly while they preserve
their own energy for growth.

Small agile fish use the jellies
as moving reefs for protection,

darting between tentacles
without ever touching them.

Nudibranchs, which are sea slugs
covered in protective slime,

can actually steal the jelly's defenses
by eating the cnidocytes

and transferring them
to specialized sacks for later use,

as weapons against their own predators.

Even humans might benefit
from the sting of a jellyfish one day.

Scientists are working on manipulating
cnidocytes to deliver medicine,

with nematocysts rarely 3% of the size
of a typical syringe needle.

So, the next time you're out
in the ocean, be careful.

But also, take a second
to marvel at its wonders.