If aphids could recite Shakespeare, they might favor this rousing cry: "Once more unto the breach, dear friends, once more; or close the wall up with our [aphid] dead." Researchers have discovered that the social insects send soldiers to repair holes in the plant tissue where they make their homes, and that some of the soldiers never return from these "suicide missions." Some aphids cause their plant hosts to form hollow swellings called galls within which the larvae mature. A hole in the gall's wall threatens the larvae's cozy and protected home, and causes soldier aphids to rush to the spot. There they excrete body fluids that represent about two-thirds of their body mass, and mix the fluids with their legs to form a scab that patches the hole.
Many of the soldier aphids, of the species Nipponaphis monzeni, die from the significant loss of body mass. Many others get stuck in the viscous fluid and fail to escape. Like workers on the Great Wall of China, they simply become a physical part of the building work [BBC News].
Is the soldiers' sacrifice worth it? Lead researcher Takema Fukatsu says yes.
In the new study, published online today in the Proceedings of the Royal Society B, his team shows that aphids in 18 out of 22 repaired galls were doing just fine a month later. Only one of 12 colonies survived without the repairs [ScienceNOW Daily News].
After the initial patch is formed, the soldiers continue to cluster around the job site, and apparently stimulate the plant to finish repairing the gall. Explains Fukatsu:
"After the hole is plugged by solidified body fluid, soldier nymphs manipulate the growth and regeneration of plant tissue nearby the breach in an intricate manner, which leads to complete sealing of the hole by plant tissue" [BBC News].
Researchers say that when soldiers inside the gall were prevented from hanging around the patched hole, tissue regeneration did not occur. This is a particularly impressive manipulation, researchers say, because the plant has no use for the gall, and would be better off expending its energy in other ways.
The big mystery now is what substances the soldiers secrete to stimulate plant healing. Fukatsu hopes they'll include novel compounds that could prove useful for manipulating plant cell and tissue cultures [ScienceNOW Daily News].
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