A hydrostatic skeleton is a skeletal system usually seen in aquatic life forms. It is unique because it is not hard like a human skeletal system, which is made up of bones. It is filled with fluid, which gives the animal its shape.

Structure

Hydrostatic skeletons are made up of a body cavity filled with fluid and a wall made of muscle that surrounds the cavity. Most generally look like a hollow tube, like a worm.

Hydrostatic Animals

Hydrostatic skeletons are seen in animals that include many different worms, octopuses, jellyfishes, sea anemones, polyps and tunicates.

Movement

Animals with hydrostatic skeletons move by contracting the muscles in the wall that force the fluid into different parts of the body, which changes the shape of the body. As the shape changes, the body moves. One end of the body extends toward where the animal is moving to and the other contracts away from where it is leaving.

Benefits

Hydrostatic skeletons have the benefit of being able to drastically change their shape to fit their environment, so they can squeeze into very tight spaces and hide from predators or wait for prey. They also can absorb nutrients and water and get rid of wastes through their skin, which helps them conserve energy.

Part-time Hydrostatic Animals

Some crustaceans, which normally have an exoskeleton, use a hydrostatic skeleton for some of the time. When the crustaceans shed their exoskeleton, they use a hydrostatic skeleton to move around while they wait for the new exoskeleton to harden.

Source:

Bookrags

The Journal of Experimental Biology