Sea spiders - amazing underwater inhabitants. Despite some similarity with land spiders, maritime belongs to a completely different class. They do not fly underwater traps, and slowly crawling on the seabed, finding their prey - small rahes, sedentary inquiries and various mollusks. Sea spiders live in the seas and oceans at various depths and are of size from a pair of millimeters to several tens of centimeters.
It is interesting to be a digestive system of sea spiders: their intestines are distributed evenly throughout the body, entering each leg until its end. In addition to the digestion, it performs the most important function: like a circulating system of people with its help by the body is carried out by the current of the hemolymphs enriched with nutrients - the elevation of blood in mammals.
The movement of hemolymphs is created by reducing the intestines, but the most amazing thing is the fact that the breath of sea spiders is carried out through the tips of the legs: it is from there that the hemolymif enriched with oxygen is directed to the body, resembling the wave-like intestinal movements. Specialists were able to observe this picture by adding special glowing labels into the liquid, with which it became visible to circulation inside the body.
It turns out that during the evolution, sea spiders acquired the ability to breathe through the legs that perform the gills function. For a long time it was believed that these animals have diffuse breathing, absorbing oxygen through their exoskeleton. But in this case, it remained incomprehensible as large individuals of spiders in several tens of centimeters could obtain a sufficient amount of oxygen through imperfect diffuse breathing. Now scientists know that during the evolution, sea spiders acquired a completely different type of breathing.