According to new research on the German cockroach (Blattella germanica
), nerve cells that normally detect bitter, potentially toxic compounds are now responding in a similar way to glucose.
The implication of this is that these developed cockroaches will avoid taking up bait, according to the New York Times
. This is because the “bitter” reaction suppresses the “sweet” response from other nerve cells, and the roach stops eating. If the cockroach begins to react in a similar way to “sweet” sensations, then it will not eat the poison in the trap.
It has been speculated by the science team involved that cockroaches have evolved to avoid the traps. Cockroaches do not detect taste with tongues, as animals do, but instead use hairlike structures that grow in lots of spots on their bodies.
It is possible that the evolution has come about via a mating of the one or more commonly known cockroach species with some other as-yet-unidentified roach species that does not eat glucose. An alternative view is that something in the bait material has triggered a genetic variation in cockroaches that has been passed down through successive off-spring.
This finding explains to etymologists why a trend is developing whereby cockroaches are seemingly avoiding tried and tested bait traps.
The research has been undertaken by entomologist Coby Schal of North Carolina State University in Raleigh. Quoted by the BBC
, Dr Schal said: “The cells that normally respond to bitter compounds were responding to glucose in these [mutant] cockroaches. So they're perceiving glucose to be a bitter compound. The sweet-responding cell does also fire, but the bitter compound actually inhibits it - so the end result is that bitterness overrides sweetness."
The findings have been published
in the journal Science. The paper is titled “Changes in taste neurons support the emergence of an adaptive behavior in cockroaches”.