Echinoderms

Q: What are echinoderms ?
A: Echinoderms are radially symmetrical animals which are only found in the sea. The word 'echinoderms' means "spiny skin'' in Greek. Most, but not all, of them have spiny skin. Starfish, sea stars, brittle stars, sea urchins, feather stars, sea cucumbers and lamprometra (feather star) are types of echinoderms.





Q: What are sea cucumbers ?
A: Sea cucumbers are creatures which resemble a football. They are generally found on their side at the bottom of the ocean. Sea cucumbers belong to a sub-category of echinoderms known as holothuroidea. They feed upon plankton and other organic matter. Some stay in a current that brings a steady supply of food, and spend hours there. The tentacles open up and gather food in the current of the ocean. The sea cucumber uses some tentacles to eta, while the other tentacles collect food. Most sea cucumbers are poisonous.

Q: How do sea cucumbers protect themselves ?
A: The sea cucumber has an unusual way of defending itself. It throws out all of it's internal organs! This either scares off or satisfies the predators. The sea cucumber has the ability to grow another set of internal organs. Some sea cucumbers even secrete a sticky substance in order to defend themselves against their enemies. If anyone gets this sticky material on its body, it will not be able to remove it unless the skin is shaved off.


Q: What is a starfish ?
A: Sea stars are sometimes called starfish, though they are not really fish as they do not have vertebrae and fins. They are usually two sub-types of sea stars - asteroids which are the true sea stars
and sun stars. Ophiuroideas are brittle stars and basket stars. Each sea star has hundreds of tiny feet at the bottom of each ray. These tube feet are also known as podia. Theses tiny feet are filled with sea water. Apart from this, the vascular system f the sea star is also filled with sea water. By slowly moving water from the vascular system into the tiny feet, the sea star can move its foot by expanding it, and thus it moves around. Star fish eat many things. Their diet consists of barnacles, snails, sea urchins, clams and mussels.


Q: What do brittle stars look like ?
A: The brittle star is also known as the serpent star. It is a spiny, hard-skinned animal having long arms, which lives on he rocky sea floor, in the shallow waters to greater depths. They are of many colours, including shades of brown, red-brown, yellow and cream. If a brittle star's arm is cut off it has the capability to regenerate. Brittle stars which have multiple-forked arms are also known as basket stars. Most brittle stars are less than 1 inch (2.5cm) in diameter having a hard exoskeleton. They don't have a brain; instead have a simple ring of nerve cells which carries out information all around the body. Tube feet located along the arms, sense light. They feed on decaying matter and plankton. Some brittle stars can also kill small animals. Compared to starfish, brittle stars have a much smaller central disc with no anus. Wastes are disposed off through the mouth which is centrally located on the underside.