Scientists have learned about the unusual form of communication of marine animals using polarized light.

    Mantis cancer is a very unusual creature. This marine animal looks very special, and its capabilities are not quite standard. Wikipedia speaks of this crustacean as follows: “Praying mantis cancer (Latin: Oratosquilla oratoria) is a large carnivorous, ornate crustacean of the genus Oratosquilla of the family Squillidae. Length up to 20 cm, weight up to 200 grams. It occurs in the Western Pacific Ocean from the islands of Taiwan and the Ryukyu to the Peter the Great Bay (Sea of ​​Japan), which is its northern border of distribution. It lives in shallow water at a depth of 5 to 37 meters. It is a predator, digs holes in which it spends most of its life. Eyes contain 16 types of photosensitive cells (for comparison, human eyes - 3 types). ”

    In addition, animal claws are a dangerous weapon that can crush both mollusk shells and aquarium glass. The impact area of ​​the claw consists of hydroxyapatite crystals. Then comes amorphous hydroxyapatite and chitin. This structure and the structure of the claw allow the crustacean to deliver powerful blows to enemies or its own victims. But the mantis shrimp has another interesting feature - some parts of their body are covered with reflective material, which is able to reflect light, polarizing it in a special way. Cancer is also capable of perceiving this kind of radiation, using it to communicate with fellow tribesmen.

    According to a new study, circular-polarized reflected light is used by a mantis shrimp to let competitors know about their presence.

    “For birds, color communication is common, there are also many brightly colored animals in the ocean. All of them to one degree or another use this feature for communication. This is a form of communication that we understand. But now we have discovered what is a completely new way of communication in the animal world, ”said Professor Marshall, the scientist leading the study.

    Cancer has circular polarizing structures on the body, in particular, on the limbs, head and tail. These parts of the cancer body are most visible, they are seen by a competitor in case of a meeting.

    “These crustaceans live in reef niches. They prefer to hide, and do not like to be in an open place, ”says Marshall.

    To test their assumption that crayfish communicate using polarized light, scientists placed mantis crayfish in an aquarium, where a polarized light source was located in the opening where the crustacean could hide. As a result, in 68% of cases, cancers avoided this place.

    “If you mark the hole with polarized light, with circular polarization, the crayfish will not want to go there. They know, or think, that they know that there is already another mantis cancer, ”the professor comments on the discovery.

    The case of mantis shrimps is the rarest, but still not the only one. Polarized light is also used by crabs of the species Uca stenodactylus. These crustaceans can identify and identify objects at the bottom, depending on how much polarized light is reflected.

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