Stop Shark At­tacks With Vomit!

The hag­fish has de­vel­oped a slimy sub­stance that it uses to de­fend it­self against sharks and other preda­tors. The slime blocks the gills, mak­ing sharks cough and strug­gle to breathe.

Science Illustrated - - SCIENCE UPDATE -

The hag­fish be­longs to a group of an­i­mals that bi­ol­o­gists con­sider the most prim­i­tive among ver­te­brates. But when they must pro­tect them­selves against en­e­mies, they turn out to be rather so­phis­ti­cated.

The hag­fish re­leases a slimy sub­stance that makes larger preda­tory fish gasp for breath. The slime swiftly blocks the preda­tory fish’s gills, so it can­not ab­sorb oxy­gen. When a hun­gry shark dares to en­ter its teeth into a hag­fish, it will hence very quickly let go of its prey again, al­low­ing the hag­fish to es­cape un­harmed.

Bi­ol­o­gists from three US uni­ver­si­ties have stud­ied the sce­nario via sev­eral video record­ings and were in­spired to take a closer look at the skin of the hag­fish to find out how it can es­cape the at­tacks so eas­ily. The sci­en­tists as­sumed that the skin was very sturdy and hence dif­fi­cult to pen­e­trate for the teeth of the preda­tory fish. So, they tested the break­ing strength of hag­fish skin, com­par­ing it to the skin of 21 other fish species. How­ever, the study showed that hag­fish skin is not any stur­dier than that of other species. When the hag­fish es­capes preda­tor fish teeth al­most un­harmed, it is in­stead due to the fact that the skin is very loose.

Not only the sci­en­tists’ video record­ings, but also other ob­ser­va­tions demon­strate the ef­fi­ciency of hag­fish de­fence mech­a­nisms. When bi­ol­o­gists study the stom­ach con­tents of other large preda­tory fish, they very rarely come across hag­fish re­mains.

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