Name: The one thing stopping jellyfish from taking over - Mariela Pajuelo & Javier Antonio Quinones
Uploaded: 2023-10-19T06:27:55.000Z
Duration: 5 min 35 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Over the past two decades, jellyfish have begun to overwhelm our oceans.

In New Zealand, divers swat off millions of stinging jellyfish

In Sweden, a massive cluster of moon jellyfish

shut down one of the world's largest nuclear reactors

And in the Sea of Japan, thousands of 200 kilogram Nomura's jellyfish

with bells two meters in diameter swarm fishermen,

Around the world, these animals voraciously consume fish eggs and larvae,

routinely undermine marine farming efforts,

and outcompete adult fish by consuming the resources they need to survive.

If things stay on their current trajectory,

we could be headed for a future where the entire ocean is thick with jellyfish.

So, is there anything that can keep these gelatinous creatures under control?

There are a wide range of marine animals that feed on jellyfish,

but sea turtles are among their most ancient predators.

And while every known species of sea turtle preys on jellyfish

none consume quite as many as the leatherback.

Leatherbacks are the largest species of sea turtle,

and they eat jellyfish almost exclusively,

devouring well over 1,000 metric tons of them over their roughly 50-year lifespans.

This is particularly remarkable because jellyfish are 95% water

needs to eat roughly 400 kilograms of jellyfish every day.

That's roughly the same weight as a grand piano.

And while some sea turtle species have been documented

selectively eating their preys' protein-rich gonads,

mowing down huge swaths of unsuspecting jellies.

Normally, jellyfish aren't quite this defenseless.

Most species have tentacles covered in cells called cnidocytes,

which contain venomous harpoons coiled and ready to launch.

These barbed structures,  known as nematocysts,

Jellyfish frequently use this sting to paralyze and kill their food,

and it can also irritate the skin of would-be intruders.

But it's completely useless against sea turtles.

Most of these reptiles have thick scales covered in keratin—

the same material that makes up nails and claws.

This leathery armor protects their skin while they hunt,

and any captured prey that tries to escape is impaled

on the keratinized spikes lining the leatherback's esophagus.

For most sea turtles, these adaptations make individual jellyfish easy prey.

However, a jelly population's true defense mechanism

Almost all jellyfish species have evolved to reproduce both sexually and asexually,

allowing them to increase their numbers with or without a partner.

jellyfish reproduce constantly throughout the year.

species often reproduce all at once in a massive bloom,

where jellies multiply at alarming rates.

And humanity is making these blooms much more frequent.

Fertilizer runoff from farms introduces chemicals

that simultaneously kill other fish and prompt blooms.

High water temperatures caused by climate change

speed up jellyfish reproduction and extend the reproductive season.

Meanwhile, both marine construction and pollution

dramatically increase the surface area for jellyfish polyps

All these issues require a wide range of policy-based solutions.

But one major way to prevent jellyfish populations from getting out of hand

Small-scale fisheries that are essential to communities in Mexico and Peru

which unintentionally capture and kill hundreds of sea turtles each year.

In the Eastern Pacific, these practices could drive leatherbacks to extinction

Fortunately, some researchers have already developed inexpensive tools

Attaching green LED lights to gillnets has proven useful

for allowing sea turtles, dolphins, and even seabirds to avoid fishing gear.

Solutions like this should  allow small-scale fishers

while minimizing their impact on our leathery ocean defenders.