The Loh Down On Science

How starfish keep their cool out of water

Pincebourde et al., J. of Exp. Biol., 2013.

Figure 1 illustrates the relationship between average arm temperature and central disk temperature in sea stars. Notice the progression, as temperature increases, from individuals with intact arms (black circles) to individuals with lost arms (blue triangles) to individuals who died (red squares). Caption modified from original for clarity.

Can sunbathing lead to … limb loss?!

This is Sandra Tsing Loh with the Loh Down on Science 

Saying, it can if you’re a sea star.

During low tide, sea stars—AKA starfish—may bake in the sun for hours. How do they keep their cool?

French marine scientist Sylvain Pincebourde knows.  He collected starfish from the coast and housed them in an empty lab aquarium.  Heat lamps served as the sun.  He let them simmer at various temperatures.

At hotter treatments, he noticed something, uh, fishy.  His subjects’ limbs started falling off! What the?!  Some lost three of their five appendages.  The, uh, cut-off temperature? About 91 degrees Fahrenheit.

Turns out limb loss actually aids survival. A heat-sensitive camera revealed why. The crispy critters’ arms were always four degrees toastier than their central disks. Their feelers take most of the heat!  Which can fry them to the point of amputation.  But that saves their vitals. And heck, those limbs grow back!

But for the rest of you, do not try this at home.  And sun screen?  Still recommended!

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*****Today, Thursday, from 2-3 p.m. on the LDOS blog: Sandra chats with author Amy Alkon about her book I See Rude People.*****

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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