The Loh Down On Science

Understanding how animals made the transition from water to land

Image courtesy of Kawano & Blob, Soc. for Integ. & Comp. Biol. Symp., 2013.

Salamander (left) and mudskipper (right) walking on a force platform.

Pop quiz:  Why did animals with limbs rather than fins become the first land dwellers?

This is Sandra Tsing Loh with the Loh Down on Science, saying, it's a fair question.

Both likely evolved their appendages underwater.  So why did only limbed animals adapt successfully to land?

Enter biologist Sandy Kawano at Clemson University, in South Carolina. She analyzed two modern animals that resemble early amphibians.

On evolutionary branch number one:  Tiger salamanders!  Amphibians with four equally-sized limbs.  Branch two:  Mudskippers!  Weird fish that breathe through their skin and can leave the water.  They use their front fins to pull themselves around tidal zones.  Picture the motion of walking with crutches.

Kawano let both critters crawl on a force platform.  It measures pressure, like a bathroom scale, but in all directions.

And?  Salamanders distributed weight vertically, and equally, over all four limbs.

Meanwhile, mudskippers’ "walking-on-crutches" type of crawl?”  Concentrated all the pressure on those front-fin bones.  Which may be okay for short stints, but probably isn't sustainable over the long haul.

And that's the story about how surf became turf!  More or less.

***** For more 90-SECOND SCIENCE FACTS, click here.*****

The Loh Down on Science is produced by LDOS Media Lab, with 89.3 KPCC. And made possible by the generous support of the Gordon and Betty Moore Foundation.

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