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Crabs are short-tailed crayfish, whose appearance is characterized by strongly bulging eyes, a cephalothorax protected by a durable shell, and as many as five pairs of limbs.
Crabs live in all the seas of our planet. Also, found in fresh waters.
The peculiarity of land crabs is that the part of the shell covering their gills is swollen and filled with blood vessels.
This evolutionary adaptation allows them to extract oxygen from the air, much like the lungs of vertebrates.
The eyes of crabs have a complex structure. They consist of a huge, up to three thousand or more, individual eyes, or facets.
Each facet sees only rays incident perpendicular to it.
Crabs see the world around them as a repeating mosaic - they have compound eyes, that is, consisting of many light-sensitive elements. In addition, the deeper a crab lives, the larger its eyes are, as a rule, to catch more light.
The lifespan of a large crab is long and is usually 25-30 years. Although some individuals can even live up to 100 years.
Shore crabs can navigate and remember previously traveled routes, says Biology Letters.
Crabs eat both animal and plant foods. For example, fruits, pieces of sea fish, shrimp, mussels, squid, plant leaves, seaweed.
Previously, we told interesting facts about starfish.