ZOO-ology column: Open mind to hairy frogs, hagfish

By Judie Farnsworth
April 1, 2012 at 10:05 p.m.
Updated March 31, 2012 at 11:01 p.m.

Scientists believe that the hair on the hairy frog's body is used to help absorb oxygen from water.

Scientists believe that the hair on the hairy frog's body is used to help absorb oxygen from water.

"In all things of nature there is something of the marvelous"

- Aristotle

Sometimes the marvelous need an open mind to be appreciated for more than just weird. Consider the hairy frog and hagfish.

The hairy frog, sometimes called the horror frog, is a Central African species. As if thoughts of a hairy frog aren't weird enough, how about a hairy frog that breaks its own bones to form claws? You have to admit this is an attention-getter.

Scientifically known as Trichobatrachus robustus, its claws are bone rather than the keratinous material of most claws (and our nails). They're extremely sharp, secured in bony nodules near the tip of the toes and connected to muscles.

When the muscles tense, the claws break through the bony nodules and toe pads, creating dangerous spiked feet. There are species of lizards and salamanders that have spines growing naturally through the skin, but this creature's ability is unique.

Now - about the hair. It's not exactly lush curling tendrils, but hair-like strands of skin containing blood vessels. It's found on the flanks and thighs of breeding males and is thought to increase surface area for absorbing oxygen from the water. Although basically a land animal (terrestrial), the frog spends extended times in the water when breeding. There's more to be learned about this "marvelous" creature as it is studied.


Hagfish are a species that might exemplify the phrase, "I've been slimed," or the coined word, "iieeeuu."

Sometimes called slime eels, hagfish live in the oceans, preferring colder waters. These primitive creatures are considered living fossils, being similar to those of 300 million years ago. They do hunt, but often feed by burrowing into dead and dying fish and eating from the inside out - one of their less than endearing habits.

They are an alarmingly fascinating (albeit repugnant) animal and are being studied (notably) for their slime. When threatened, they are quick to ooze copious amounts of mucous-like goo from hundreds of pores. It sometimes encloses them cocoon style.

The slime expands when mixed with sea water and can suffocate an attacking predator by clogging its gills. Marine animals learn to avoid hagfish. Those that even get close may swim off gagging. An adult hagfish is a super slimer and able to fill a milk jug in minutes.

So - you may ask - what happens to a self-slimed hagfish. Does it suffocate too? It could, but not to worry. When the coast is clear, the hagfish has a great slime removal technique. (This is the marvelous part) It ties itself into an overhand knot which it slides down its body. The traveling knot de-slimes the fish and a few sneezes clear its gills. A knot may also be used for pressure when pulling at food.

Scientists have discovered that hagfish slime is reinforced with very strong and sometimes foot long miniscule fibers. They are studying it for possible applications in creating tough synthetic materials. So maybe Aristotle was right - but I wonder if he ever met a hagfish.

You can enjoy many marvelous bits of nature when you visit The Texas Zoo.


Zintzen, Roberts, Anderson, Stewart, Struthers & Harvey. 2011. Hagfish predatory behaviour and slime defence mechanism. Scientific Reports. http://dx.doi.org/10.1038/srep00131



Hairy frog photo credit: Gustavocarra for Wikimedia Commons

Hairy frog foot photo credit: David Blackburn

Hagfish photo http://cdn.physorg.com/newman/gfx/news/hagfish.jpg

Hagfish slime photo courtesy of Chris Ortlepp.

Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.



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