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What is Phylum Echinodermata?

• Echinoderms are animals that have scaly and spiny

For example, starfish, sea cucumbers, etc.

• They belong to the phylum Echinodermata. They are usually marine in habitat, except starfish which often come up to the

Echinoderms

• The body of echinoderms is triploblastic and It originates from three embryonic layers and has a true coelom.
• They have a radial symmetry in their adult stages, although some may exhibit bilateral symmetry in their larval

Which systems are present in Echinoderms?

• Echinoderms have a well-developed digestive system which begins with the
• The digestive system has a proper oesophagus, stomach, intestine, rectum, and an anus at the end. Some organisms can also have a cardiac stomach, a part that can come out of the body, digest food, and then get back
• Some echinoderms show the presence of Aristotle’s lantern around the It is a

circularly arranged dental complex which has structures that can scrape out substances.

For example, most sea urchins scrape out algae from surfaces of rocks by a dental apparatus.

• In some of these organisms, Aristotle’s lantern can have venomous

Digestive system of Echinoderms

Aristotle’s lantern

• The excretory system in echinoderms is not well-developed. The nitrogenous wastes are diffused through the respiratory system in most
• The circulatory system, in echinoderms, has two specialised circulatory systems:

Haemal circulatory system – It contains cells involved in circulation and brings about the transport of food, nutrients, and gases throughout the body.

Water vascular system – It is a specialised system found in echinoderms which helps in the movement and locomotion of the animal and the transportation of food and other substances in the body.

Circulatory system of Echinoderms

• Echinoderms have a radial nervous
• A typical brain is absent in these animals, but most of them have ganglia to take over. The ring-like ganglia are present surrounding the mouth and the nerves extend to each arm regulating functions as and when
• The sexes in echinoderms are usually separate. Fertilisation occurs externally as sperms and eggs are released in water in coordination. Some species exhibit internal fertilisation as

Nervous system of Echinoderms