Name: 不気味すぎる寄生虫4種 (4 Parasites Too Creepy to Exist)
Uploaded: 2021-01-14T10:47:42.000Z
Duration: 13 min 25 s
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Of all the strategies life has developed for survival,

A parasite is an organism that makes its living

taking resources from another, called the host.

between ⅓ and ½ of all life on Earth is parasitic,

although there's still a lot we don't understand.

What we do know is that the unique challenges

and opportunities that come with parasitism have led

to the evolution of some truly strange and

Fair warning: some of what you're about to hear

Case in point, the first parasite on our list is

a crustacean that latches onto a fish's tongue

They're often called “tongue-biting isopods,”

and they belong to a group of crustaceans called cymothoids.

This group includes many species that attack fish,

usually infecting the skin, muscles, or gills and

particularly disturbing habit of going for the mouth.

Since there's limited space in a fish's mouth,

this approach is strictly a first come, first served sort of engagment.

These crustaceans all start out as free-swimming, male larvae.

They wander around until they find a fish and settle in its gills.

There, they check to see if the mouth is unoccupied.

If so, they move in and bite down on the fish's tongue!

Well, technically fish don't have true tongues.

They have a bony structure called a basihyal,

but “basihyal-biting isopod” is not nearly as catchy.

Anyway, once the male parasite has affixed itself,

it transforms into a much larger adult female!

And that's where the isopod lives its life,

sucking nutrients from the fish's bloodstream

settle down in the gills and make only occasional trips

So a fish with an infection usually ends up with

1 female in its mouth and as many as 5 males in its gills!

but it is apparently a successful strategy.

These parasites are known to infect numerous

species of fish, from snappers to grunions to croakers.

It probably won't surprise you to find out that having

a bug stuck permanently on your tongue has some side effects.

A 2013 study found that infected fish tend to be

smaller and less healthy, but not for the reason you might think.

Scientists expected that the infected fish would

have trouble eating, but that doesn't seem to be the case.

Instead, they think the fish is having trouble breathing.

The female isopod can grow up to three centimeters,

taking up a good part of the volume of the fish's mouth

and blocking the flow of water to its gills.

And the males stuck in the gills don't help either.

So one nickname given to these parasites -

“snapper-choking isopods” - might be spot on!

But when it comes to making a host unhealthy,

this next parasite takes it to a whole new level.

In a 2002 study, a team of scientists noticed that

at certain sites in northern California there were unusually

high numbers of amphibians with deformed legs.

They spotted frogs and salamanders with extra legs,

legs that hadn't formed properly, or even legs that were missing entirely.

The scientists wondered if pollution was to blame,

but a closer look revealed that the deformities

correlated not with pollutants, but with worms.

The ponds with the most malformed amphibians were

also harboring an infection of trematodes,

a type of flatworm, particularly one named Ribeiroia.

These little parasites have a complicated life cycle

that involves three hosts at different stages of the worms' lives.

They start out as eggs inside the poop of birds or mammals.

When that poop ends up in water, the eggs hatch

and little swimming larvae infect snails,

reproducing asexually to create hundreds more of themselves.

These swarms of worms emerge from the snails

and swim around to find a tadpole or young salamander,

where they tend to infect the skin near the developing limb buds.

Larval amphibians like tadpoles start their lives

limbless and grow legs when they metamorphose into adults.

But if they're infected, the parasites get in the way

of this development and the legs come out all wrong!

the ponds with the highest Ribeiroia numbers

In the most extreme cases, the researchers saw

2 tree frogs that had each grown 4 extra legs.

Scientists worry that as humans have been

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不気味すぎる寄生虫4種 (4 Parasites Too Creepy to Exist)

essentially

incredible

apparently

strategy