Blue and white workers of Neocapritermes taracua. The picture shows a soldier, two white workers (ww) and two blue workers (bw) with two blue spots between their thorax and abdomen. Image courtesy of R. Hanus
(Phys.org) — A new study of termites has revealed that older workers are equipped with suicide packs of chemicals on their backs to fight off intruders.
An international team of researchers, led by Robert Hanus and Jan obotnk of the Academy of Sciences of the Czech Republic in Prague, looked at Neocapritermes taracua termites, native to French Guiana, and discovered that many of the workers had varying sizes of blue spots on their backs. The blue spots are external pouches containing copper-containing proteins secreted by specialized glands located on top of the salivary glands. When the researchers picked up the termites using forceps, they were surprised to find they burst, releasing a toxic sticky droplet along with fragments of intestines and internal organs.
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This movie shows one worker of Neocapritermes taracua rupturing its body after being attacked by workers of Embiratermes neotenicus. The worker emit a ball-like droplet of haemolymph (marked with the red arrow), together with a part of its internal organs, such as the intestine (visible as the dark spot). Before body rupture, a pair of blue crystals is easily distinguishable in the N. taracua worker, but these crystals rapidly dissolve in the droplet of haemolymph and disappear. Video courtesy of R. Hanus
The researchers found that when a worker with blue spots was attacked by invading termites, it ruptured its body wall, releasing the contents of the blue pouches, which mixed with salivary fluid to form a drop of chemical so toxic that it paralyzed or killed most of the invading termites that touched it. The blue-spotted worker termites died in the process. Workers with no spots also burst when threatened, but less readily and less effectively since the toxins released were much less potent than that from the blue spots.
Blue and white workers of Neocapritermes taracua. The picture shows two soldiers, two white workers (ww) and three blue workers (bw) with two blue spots between their thorax and abdomen. Image courtesy of R. Hanus
The study also demonstrated that the number and size of the blue pouches increased with the workers age. The workers capacity to do other work such as gathering food diminishes with age, and as they become less useful to the colony in other ways, and less able to defend the colony using their jaws, their capacity to act as suicidal defenders of the colony increases along with their willingness to sacrifice themselves.
Suicidal explosive behavior has been seen before in termites, but the contents of the intestine are usually expelled rather than toxins as found in the N. taracua termites, and the enemy termites are usually inconvenienced and slowed down rather than killed.
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Aging worker termites explode themselves in suicide missions