The Loh Down On Science

How cockroaches are outsmarting us

Wada-Katsumata et al., Science, 2013.

The responses of cockroaches to tasting 10 different subtances, from salt to sugars to caffeine. Wild-type means normal cockroaches. Notice how glucose-averse roaches reject the sweet samples. GRN response indicates which taste neurons ("gustatory-receptor neurons") fired in response to the sample. Colored dots correspond to different taste neurons. Blue=sweet; red=bitter.

Are cockroach traps failing you?  This may be why!

This is Sandra Tsing Loh with the Loh Down on Science.

People typically fight cockroaches with poisoned baits.  These contain sugar, which attracts roaches.  But some buggers have lost their taste for the sweet but deadly treats.  Curses!  Why? 
Entomologists from North Carolina State University have found out.

Scientists already knew roaches can detect sweet, bitter, and salty tastes.  The North Carolina team wired normal and bait-avoidant roaches to electrodes.  Eek!  Why?  To monitor when specific taste receptors fired.  Then they exposed the roaches to various tastes. 

And?  When taste buds in normal roaches met sugar, their sweet receptors fired, correctly saying, "Sweet! Yum!"   But, when taste buds in bait-avoidant roaches sampled sugar?  Their bitter receptors fired, saying, "Bitter! Yuck!"

So the brains of bait-avoidant roaches are misinterpreting sweet as bitter:  Nein!  Nyet!  Avoid!  Scientists call this behavior "glucose aversion."  And these roaches can pass the trait on to their gajillion offspring.

Which is a lot of roach motels with a lot of tiny little vacancies.

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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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