Eyeless worms see color | Science and life


Vision in different animals is arranged in different ways, and the more complex it is, the more the animal sees. For example, in our eye to distinguish colors there are cones – three types of photosensitive cells. Some cones react most strongly to violet-blue, others to green-yellow, and still others to yellow-red. If the eyes are designed quite simply, if there are actually no eyes, but there is just a group of light-sensitive cells, can there be complex color vision? It is unlikely, usually such animals distinguish light from darkness, they can feel different illumination, but no more.

However, there may be secrets here. Researchers from Yale University write to Sciencethat eyeless roundworms are nematodes Caenorhabditis elegans – avoid certain types of light waves – that is, they simply do not like some colors. Living in soil and in piles of rotting organic matter, they feed on bacteria. Among the bacteria there are not very tasty ones, for example, the poisonous Pseudomonas aeruginosa Pseudomonas aeruginosa… The worms somehow distinguish Pseudomonas aeruginosa from other bacteria and avoid approaching it.

The authors of the work drew attention to the fact that the toxin of Pseudomonas aeruginosa is blue. At the same time, it cannot be said that worms always dig in the dark, some kind of light makes its way to them, especially if they crawl in the surface layers of the soil or compost heap. That is, it can be assumed that nematodes distinguish unpleasant bacteria by the blue color of their toxin. Researchers genetically engineered to replace the colored toxin in Pseudomonas aeruginosa with a colorless one – and the worms ceased to avoid such bacteria. But when the bacteria were simply deprived of the toxin, and the bacterial colony was painted with safe blue paint, the worms also ceased to be afraid of such bacteria, although they were blue. Moreover, if the “discolored” Pseudomonas aeruginosa sticks were highlighted in blue, the worms began to avoid such bacteria.

It also turned out that the behavior of nematodes depends on the spectral relationship between blue and yellow light. And not all “breeds” C. elegans equally avoid blue. For example, if we take not laboratory, but wild lines (varieties) of worms, then among them there will be those that do not react to blue in any way.

But nematodes C. elegans eyeless. How do they feel blue then? It turned out that the aversion to blue depends on two genes, jkk-1 and lec-3… Different organisms, including humans, have their own varieties of both of these genes. Neither encodes opsins, light-sensitive proteins that work in the eyes. But jkk-1 and lec-3 help cells respond to stress, particularly UV stress. Probably, somehow proteins jkk-1 and lec-3 in nematodes are able to sense blue and its share in light emission. If the degree of blue seems dangerous, the worms will try to crawl away from the blue place, or at least there is nothing there.

All this looks all the more surprising if you remember that the nematode C. elegans Is one of the most studied organisms. Her genome has been read for a long time, all her neurons are counted, together with yeast, fruit flies, E. coli, etc. she is called the workhorse of biology – a huge number of molecular genetic, cellular and neurobiological experiments are performed on it, literally everything is studied on it. , from general mechanisms of individual development to memory. But here’s the ability C. elegans to distinguish blue color has not been paid attention to. Perhaps, if you look closely at other simply arranged invertebrates, it turns out that in some respects they are not as simple as they seem. For example, we once wrote about caterpillars that feel color with their entire skin, because visual genes work literally all over their body.

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