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Carrot Cockroach
before March 9, 2006


American cockroaches (Periplaneta americana) are unique insects. First, they are primal insects on our planet. Second, these big (up to 4 cm length) red creatures are the fastest runners among all terricole insects. The world record set in 1991 by an American cockroach (Periplaneta Americana) is 5.4 kmph. This means that during one second the champion cockroach covered a distance exceeding his own body length 50-fold! To achieve this outstanding result an average human would have sped up to 330 kmph!

Researchers from Saint Petersburg Sechenov institute of Evolutional physiology and Biochemistry have recently found out that the American cockroach is unique not only due to his sprinter characteristics. These whiskered runners turned out to be the only ones to synthesize beta-carotene in their organism. Anyway the ability to synthesize beta-carotene was never discovered in other insects, animals or human beings. And carotenoids, as well as beta-carotene, are very important, because they are precursors of rhodopsin – visual pigment – chromofore. If mosquitoes or butterflies receive food without carotenoids, they get almost blind. Nut American cockroaches do not surrender easily!

Researchers tried to put them on a carotenoid-free diet. One group of tested insects received wheat bread, oat flakes, water and sugar, while another group was able to drink carrot juice together with said food products. However, after six months of the experiment, the cockroaches from the first test group were as healthy as the insects from the second test group and the control group (fed with common food).

Then the scientists have measured beta-carotene concentration in cockroaches’ eyes and intestines (testees were decapitated, i.e. their heads were cut off). The eyes of all cockroaches, despite their diet, turned to contain almost the same amount of beta-carotene needed for insects’ full eyesight. But as for intestines of carrot juice-drinking cockroaches, the scientists have found there 13-fold more beta-carotene than in those on a carotenoid-free diet.

The researchers, surprised by the results, have been continuing their experiment for three years. They have tested about four cockroach generations (who live quite a long life – about a year), which had to synthesize carotene, because their food lacked it – and all of them did well. Three years of living without carotene had influenced neither their eyes, nor their intestines. To prove the ability of American cockroach to synthesize beta-carotene the scientists have intraperitoneally introduced to cockroaches beta-carotene precursor – carbon-labelled mevalonic acid pyrophosphate. Their hypothesis has proved to be true – next day labelled beta-carotene was detected in cockroach eyes.

So American cockroach is able to synthesize beta-carotene. The scientists still do not know how. Perhaps, the cockroaches have necessary enzymes themselves, or some microorganisms, dwelling in the insects, perform the synthesis. Further research is needed to find the answer.

Anyway Saint Petersburg researchers propose two possible mechanisms for maintaining optimal carotenoid concentration in Periplaneta Americana’s eyes. One is carotenoid accumulation, when there is enough of them in food, the other - their synthesis de novo, when the diet lacks them.

Tags: Russian Scientists     

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