The word Echinodermata is formed from the Latin words Echinus meaning prickly, derma meaning skin and ata meaning bearing. Animals whose body is symmetrical, five-segmented, ciliated, headless, circulatory system and echinodermata are called Echinodermata. They are called conifers. Animals like sea star, sea cucumber, sea lilies, sea urchin, sand dollar etc. belong to this phase. The number of species is about 7,550. Jacob Klein (1734) named Echinodermata.
Characteristics of Echinodermata
1. Their bodies are unsegmented, cylindrical or spherical or star-shaped or flower-shaped.
2. Their body is bilaterally symmetrical or pentalaterally symmetrical or orally symmetrical or divided into five equal parts.
3. Body skin prickly. The exoskeleton is composed of numerous ossicles composed of spines and pedicellaries and the endoskeleton composed of calcium carbonate. It is covered by ciliated membranes.
4. The body is organized into distinct verbal and non-verbal levels. Five ambulacral grooves are present on the oral floor.
5. They have a water circulatory system, which carries out respiration and locomotion.
6. There are ring vessels, radial canals, medriporites, stone canals and lateral canals for water transport.
7. Their moving parts are podia. It is responsible for respiration and food absorption.
8. The Himalayan and Perihimalayantra work on circulation.
9. The body does not have a brain, respiratory system, excretory system and circulatory system.
10. All animals are marine.
11. The life cycle consists of bipinaria, auricularia, ophiopluteus, echinopluteus larvae.
Classification of Echinidermata
The order Echinidermata is divided into five classes.
1. Asteroids: Their bodies are star-shaped with five arms. Tube fit exists. Spines and pedicilli are present on the body. For example – sea star (Asterias vulgaris).
2. Ophuroidea: Their bodies are pentamerous discs. Tube fit and spine present on the body. Their arms are long. For example – Cucumaria (Cucumaria planci).
3. Echinoidea: Their bodies are hemispherical. Tube fit exists. The body has no arms. Spine present. For example, sea urchin (Echinus esculentus).
4. Holothuroids: Their bodies are long cylindrical in shape. The body has no arms, spines and pedicellariae. But tube fit exists. For example, sea cucumber (Holothuria impatiens).
5. Crinoid: Their bodies are star-shaped. The body does not have tube feet, spines, pedicillaries etc.
Some animals of Echinodermata
Sea cucumber – Holothuria impatiens
Pink feather star – Antedon bifida
Brittle Star – Ophiothrix fragilis
Sea stars- Asterias vulgaris, Astropecten euryacanthus
Snake star- Ophiura ciliaris
Sea urchin- Echinus esculentus
Cucumaria- Cucumaria planci
Sea daisy- Xylopax medusiformes
Gorgonocephalus – Gorgonocephalus arcticus
Bristle star- Ophiocoma scolopendrina
Sea pentagon- Oreaster reticulatus
Aka sea star – Anthenea pentagonula
Water vascular system
A water circulation system is a water-filled cavity. Animals of the order Echinodermata have various shaped tubes filled with water inside the body called water circulatory system. A water circulation system is created by changing parts of the silo. It transports various types of objects through it.
Ambulacral groove
A shallow groove along the digital midline of each arm is called an ambulacral groove in the phylum Echinodermata. These grooves arise from each side of the five corners of their mouth. For example, sea star (Asterias vulgaris).
Tube feet
Tube fit is the moving part. The body of animals of the order Echinodermata is equipped with two rows of tubes called tube feet. Tube feet are narrow, hollow, muscular and elastic. Tube fits occur along the length of the ambulacral groove. For example, sea star (Asterias vulgaris).
Star fish
The star-shaped animals of the order Echinodermata are called starfish. They look like stars as they have five arms. Such as Asterias vulgaris, Astropecten euryacanthus, Ophiura ciliaris.