How hagfish survive shark attacks


This video says about itself:

Hagfish predatory behaviour and slime defence mechanism

26 October 2011

Hagfishes (Myxinidae) are a family of jawless marine pre-vertebrates. Those video images taken in New Zealand revealed that hagfishes are able to choke their would-be predators with gill-clogging slime.It also shows that hagfishes are actively preying on other fish in New Zealand waters.

The video is part of a scientific paper describing this newly discovered behaviour which can be downloaded online.

From Science News:

Unusually loose skin helps hagfish survive shark attacks

Slip-sliding outer covering also aids in Houdini escapes

By Susan Milius

6:26pm, January 6, 2017

NEW ORLEANS, La. – Skin that mostly hangs loose around hagfishes proves handy for living through a shark attack or wriggling through a crevice.

The skin on hagfishes’ long, sausage-style bodies is attached in a line down the center of their backs and in flexible connections where glands release slime, explained Douglas Fudge of Chapman University in Orange, Calif. This floating skin easily slip-slides in various directions. A shark tooth can puncture the skin but not stab into the muscle below. And a shark attack is just one of the crises when loose skin can help, Fudge reported January 5 at the annual meeting of the Society for Integrative and Comparative Biology.

Hagfishes can fend off an attacking shark by quick-releasing a cloud of slime. Yet video of such events shows that a shark can land a bite before getting slimed. To figure out how hagfishes might survive such wounds, Fudge and colleagues used an indoor guillotine to drop a large mako shark tooth into hagfish carcasses. With the skin in its naturally loose state, the tooth readily punched through skin but slipped away from stabbing into the body of either the Atlantic (Myxine glutinosa) or Pacific (Eptatretus stoutii) hagfish species.

But when the researchers glued the skin firmly to the hagfish muscle so the skin couldn’t slip, the tooth typically plunged into inner tissue. For comparison, the researchers tested lampreys, which are similarly tube-shaped but with skin well-fastened to their innards. When the guillotine dropped on them, the tooth often stabbed directly into flesh.

The finding makes sense to Theodore Uyeno of Valdosta State University in Georgia, whose laboratory work suggests how loose skin might work in minimizing damage from shark bites. He and colleagues have tested how hard it is to puncture swatches of skin from both the Atlantic and Pacific species. As is true for many other materials, punching through a swatch of hagfish skin held taut didn’t take as long as punching through skin patches allowed to go slack, he said in a January 5 presentation at the meeting. Even a slight delay when a sharp point bears down on baggy skin might allow the hagfish to start dodging and sliming.

But Michelle Graham, who studies locomotion in flying snakes at Virginia Tech, wondered if puncture wounds would be a drawback to such a defense. A hagfish that avoids a deep stab could still lose blood from the skin puncture. That’s true, said Fudge, but the loss doesn’t seem to be great. Hagfish have unusually low blood pressure, and video of real attacks doesn’t show great gushes.

Hagfish blood also plays a part in another benefit of loose skin — an unusual ability to wiggle through cracks, Fudge reported in a second talk at the meeting. One of his students built an adjustable crevice and found that both Atlantic and Pacific hagfishes can contort themselves through slits only half as wide as their original body diameter. Videos show skin bulging out to the rear as the strong pinch of the opening forces blood backward.

The cavity just under a hagfish’s skin can hold roughly a third of its blood. Forcing that reservoir backward can help shrink the body diameter. Fortunately the inner body tapers at the end, Fudge said. So as blood builds up, “they don’t explode.”

Sand tiger sharks of North Carolina, USA


This video says about itself:

2 December 2016

Jonathan heads to North Carolina to explore the offshore shipwrecks of the “Graveyard of the Atlantic” which have become home to Sand Tiger sharks. The sharks are unwitting bodyguards to small fish seeking protection from predators and have developed a clever way to hide from the fish and to hover with perfect buoyancy control.

Curaçao sharks and cattle


This Dutch video is about sharks around the Caribbean island Curaçao, and cattle in Dutch nature reserve Klompenwaard.

Curaçao school children learn about sharks


This 20 December 2016 Dutch language video is about school children on the Caribbean island Curaçao learning from the Save Our Sharks organisation about sharks.

Caribbean sharks research and conservation


This Dutch language video says about itself:

19 December 2016

The project Save Our Sharks is about the protection of Caribbean sharks; they do research and provide information and education to raise awareness among the islanders of the importance of sharks.

Shark senses research


This video says about itself:

7 October 2016

In the Bahamas, Jonathan joins shark biologist Dr. Stephen Kajiura from Florida Atlantic University to perform an experiment which demonstrates how the electrosensory system of sharks works.

JONATHAN BIRD‘S BLUE WORLD is an Emmy Award-winning underwater science/adventure program that airs on public television in the United States.

Great white shark invades cage, doesn’t harm diver inside


This video from Mexico says about itself:

Great White Shark Cage Breach Accident

13 October 2016

**This may not be appropriate for our younger viewers.**

This is not our usual kids content and Gabe and Garrett did not go on this trip, this video is from my trip to Guadalupe Island (I’m their dad).

On a recent great white shark cage diving trip we experienced a very rare event, a shark breaching the side of the cage. What might appear to be an aggressive great white shark trying to attack the cage, this is not the case. These awesome sharks are biting at large chunks of tuna tied to a rope. When a great white shark lunges and bites something, it is temporarily blinded. They also cannot swim backwards.

So this shark lunged at the bait, accidentally hit the side of the cage, was most likely confused and not able to swim backwards, it thrust forward and broke the metal rail of the cage.

There was a single diver inside the cage. He ended up outside the bottom of the cage, looking down on two great white sharks. The diver is a very experienced dive instructor, remained calm, and when the shark thrashed back outside the cage, the diver calmly swam back up and climbed out completely uninjured.

The boat crew did an outstanding job, lifting the top of the cage, analyzing the frenzied situation, and the shark was out after a few long seconds. Everyone on the boat returned to the cages the next day, realizing this was a very rare event. The boat owner, captain, and crew are to be commended for making what could’ve been a tragic event into a happy ending. I’m sure God and luck had a bit to do with it too!

I want to return next year for another great white shark adventure!