Characteristics of Echinoderms in Biology: The Definition and Classification


Characteristics Of Echinoderms In Biology: The Definition And Classification – Echinoderms are a phylum of marin – e animals that includes marine animals, sea cucumbers, and some of their relatives. In general, echinoderms are a phylum of marine animals that have no members living in fresh water and on land.

This group of echinoderms is found in almost all depths of the ocean. This phylum appeared in the early Cambrian period and consisted of 7,000 surviving species and 13,000 extinct species.

Simply put, echinoderms are a type of marine animal. But, not just any marine animal, because this type of echinoderms is unique and have their own characteristics. So, it is important that you know the characteristics of echinoderms, in order to distinguish them from other phyla.

Here is a review of the understanding of echinoderms along with the characteristics of echinoderms and their classification.

Echinoderms definition biology

Echinoderms are derived from the Greek words echinos and derma. Echinos means thorns, derma means skin. So, echinoderms are animals that have thorns on the skin. Echinoderms are marine animals that live on beaches, but are mostly found on the sea floor.

Echinoderms are marine animals that are among marine animals in general, and have a wide distribution, found in all seas from the intertidal zone to the very deep sea.

The existence of echinoderms is influenced by coral reef ecosystems that are one of its habitats. Generally, echinoderms move slowly and no one lives parasites. Some live species stick (sessile). Groups of animals that include echinoderms include starfish, snake stars, sea urchins, sea lilies, and sea cucumbers.

Characteristics of Echinoderms

The following are some of the characteristics of echinoderms in general, namely:

  1. The characteristic of echinoderms is that the body consists of three embryonic layers (ectoderm, mesoderm, and endoderm). Having a perfect body cavity (coelom) or called triploblastic coelomate. The coelom is bounded by the ciliated peritoneum. The coelom contains a lot of fluid that contains amoebocyte cells, coelom united with ambulacral leg.
  2. Other characteristics of echinoderms are to have a body shape that is bilaterally symmetrical while still larvae, but in adulthood the shape of the body is radially symmetrical, some are round like balls, round flats, elongated round, or like plants, and some are equipped with long arms.
  3. The next characteristic of echinoderms is that it does not have a head and body in the oral-aboral axis.
  4. The next characteristics of echinoderms are the mouth on the ventral side and the anus on the dorsal side.
  5. Other characteristics of echinoderms are having an endoskeleton of calcareous ossicles.
  6. The next characteristic of echinoderms is to move with ambulacral, namely the tubular legs with small holes that serve to suck.
  7. The next characteristic of echinoderms is to have a perfect digestive system except for starfish that do not have an anus.
  8. The next characteristic of echinoderms is that it does not have an excretory system.
  9. The next characteristic of echinoderms is se**xual reproduction.

Classification of Echinoderms

Based on its characteristics, echinoderms are divided into 5 classes.

Asteroidea (Starfish)

Body shape like a star and live in coastal habitats. It has five short, blunt spikes on the surface of its body. Motion in the form of ambulacral leg. The body is divided into the oral side or the lower side (the place of the mouth) and the aboral side or the upper side (the place of the anus). The outermost surface layer is composed of layers of epidermal cells that are ciliated and have an endoskeleton underneath. Examples of asteroideas are Culcita (skinned starfish), Linkia laevigata (blue starfish


This animal is commonly called a snake star because it has long arms and moved like a snake. Its habitat is in deep and shallow ocean waters, especially behind rocks or buried in sand. It has a madreporite located at the bottom (mouth) and does not have an anus, so food waste is excreted through the mouth. Examples of ophiuroidea are Ophiothrix fragilis and Ophiopholis aculeata.

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It resembles lilies (sea lilies) and has five branched arms. Life attaches to the substrate and forms colonies, so that it faintly looks like a marine park. It does not have madreporite, the mouth and anus are located in the oral part. In the aboral section there are calyx, which are limestone slabs shaped like cups. An example of crinoidea is Antedon sp., and Holopus sp.


Commonly called sea urchins that live in sand and rocks. This animal has no arms, it is round in shape, it is somewhat flattened, and the surface of the body is surrounded by many thorns. The mouth and 5 teeth are in the oral section. While the anus and genital holes are in the aboral. Examples of echinoidea are Diadema Saxsatile (sea urchins) and Echinothrix sp. (Sea urchin).


It is often referred to as sea cucumbers. These animals live in sand or chalk. It has a soft body, smooth spines, and it is shaped like an elongated sac. The mouth is on the anterior, while the anus is on the posterior. Examples of holothuroidea are Holothuria scabra, and Thyone Byereus (sea cucumber).