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  • [music playing]

  • NARRATOR: As experts begin to search for other explanations,

  • they turn their attention to a series

  • of disturbing discoveries that occurred

  • in the months following the June 2012 attacks.

  • We had some dolphins that washed up already dead.

  • We weren't really sure what it was,

  • but we did hear from other states

  • that they were having the same issue.

  • NARRATOR: In fact, it turns out that over the course of 2013,

  • a total of 48 dolphins are found dead on South Carolina beaches.

  • Researchers concluded the dolphins were inflicted

  • with the morbillivirus.

  • This deadly disease suppresses the dolphin's immune system

  • and causes inflammation of the brain.

  • The result is a bizarre shift in behavior.

  • Infected dolphins have been witnessed

  • swimming in strange patterns, almost like they are drunk.

  • And additional research has shown

  • that brain inflammation in zebrafish

  • caused them to become more agitated.

  • So in 2012, could the sharks of Myrtle Beach

  • have been inflicted with a disease that

  • changed their behavior, making them

  • more likely to bite swimmers?

  • According to Dr. Dan Huber, it comes down

  • to a shark's immune system.

  • DAN HUBER: For animals, the skin is

  • the first line of defense against any type

  • of an infection.

  • So the skin is part of the immune system, essentially.

  • Looking at a section of shark skin which shows what

  • are called dermal denticles, which

  • are basically little teeth that make up the scales of a shark.

  • NARRATOR: The denticles perform a unique function

  • in the shark's immune system.

  • DAN HUBER: Dermal denticles creates

  • a very uneven shape that bacteria

  • have a hard time adhering to.

  • Because the bacteria can't adhere to it,

  • they can't form colonies.

  • And this is something that helps sharks

  • to resist bacterial infections.

  • NARRATOR: And there's also another organ that helps

  • protect sharks from disease--

  • their liver.

  • The liver produces a chemical compound called squalamine.

  • The squalamine is dispersed inside the shark's cells.

  • If a virus invades the cells, the squalamine

  • prevents it from multiplying so the virus doesn't spread.

  • And the shark doesn't get sick.

  • Scientists are even testing squalamine to fight cancer

  • in humans.

  • This remarkable immune system means

  • that sharks might be one of the most

  • disease-resistant creatures on Earth.

  • Any suggestion that the sharks could have become ill due

  • to a virus or a bacterial infection

  • isn't very likely because sharks have

  • very strong immune systems.

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B2 immune system shark immune narrator system disease

The Shark Immune System | When Sharks Attack

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    林宜悉 posted on 2020/11/09
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