The beach crab and its enemies
The crustaceans, which also include the beach crab, are a group of animals that lived as far back as 600 million years ago. Since they have many enemies, you can usually observe the animals on the coasts or banks of rivers at dusk.
Describe the anatomy of the beach crab
- The beach crab belongs to the group of short-tailed crabs. For you, this means that your abdomen is stunted and firmly tucked under the cross-oval head-chest piece.
- Crabs have a solid armor made of lime and chitin, which is also called the exoskeleton. It gives the body a firm shape and serves as an inward attachment point for the muscles.
- Since the skeleton cannot grow with the animal, it has to be changed from time to time. This process is called molting. For this purpose, a planned seam of the armor bursts and is stripped off within a few minutes. This is the time when the crab is easy prey for its enemies. Therefore, the initially soft-skinned and defenseless animal hides until the new shell has hardened after about 10 days.
- Note that the brain and heart are in the rigid head-chest piece, with the tubular back heart being the oxygen-rich blood is carried to the head, from where it is in an open blood circuit through the body to the heart flows back.
- The beach crab breathes through its gills. These are thread-like attachments of the upper part of the legs. This cluster of gills can be found under a bulge on the back shield.
- If you look at a crab, you will see 5 pairs of legs, the first pair of legs being converted into claws. With these gripping tongs, she grabs her prey, such as plants, snails, worms and small fish, chops them up and feeds them into the mouth.
- The remaining pairs of legs are walking legs. Note that female crabs carry their egg packets on their anal feet. Freshly hatched crabs hold on to their feet, which allows them to move slightly Water flow is generated, which the mother animal, the eggs and the young animals with oxygen-rich Fresh water supplied.
- Stand-up crabs have eyes that sit on moveable stems, which enables a wide field of vision. With the antenna-like first pair of sensors, they scan the environment. Note that the olfactory cells on the shorter second antennae make it easier to track down plants and prey.
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This is how the crab defends itself against enemies
- The standing crab has four pairs of legs that are the same length and allow it to run away quickly with them or to swim short distances rowing when enemies are nearby. Note that the current movement is sideways.
- It is interesting for you to know that the animals try to defend themselves against enemies such as birds or fish with the powerful grippers. The pliers are spread wide apart and hit against each other.
- The best protection from enemies is a safe hiding place for the crab. As you watch the animals, you will see them crawl into caves or burrow in the sand.
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