The echinoderms or echinodermata They are invertebrate marine animals that have an internal skeleton and can have a bilateral or pentarradial symmetry, that is, their body parts are divided into five regions and are located around a center. For instance: the starfish, the sea urchin and the sea cucumber.
exist more than 7000 species of echinoderms (and many more species already extinct) and all of them live in the sea, most of the species are part of the benthos so they crawl and swim on the seabed.
Echinoderms have calcareous plates or spiny granules spread throughout the body. Hence its name: echinoderm, which means “skin that is covered with thorns.” The calcareous plates are composed of calcium carbonate and some of them are articulated with each other (as in the case of the starfish), while others are welded to form a shell (as in the case of sea urchins).
They are animals that have neither head nor brain, however, they can perceive what is happening around them through body cells that collect information from their environment. They also do not have a heart, because their circulatory system is open and they can reproduce sexually or asexually.
Types of echinoderms
Echinoderms can be classified according to their mobility into two main subphiles:
- Pelmatozoa. They are those echinoderms that have very limited mobility or lack it. Within this sub-phylum are:
- Crinoid. They are also known as “sea lilies” and are characterized by their pentaradial symmetry, their colorful and plant-like appearance, and their feather-like arms. They live in corals or rocks and feed on small crustaceans and mollusks.
- Crinoid. They are also known as “sea lilies” and are characterized by their pentaradial symmetry, their colorful and plant-like appearance, and their feather-like arms. They live in corals or rocks and feed on small crustaceans and mollusks.
- Eleutherozoa. They are those echinoderms that can move. Within this sub-phylum are:
- Asteroid. Also known as “starfish”, they are echinoderms that inhabit all the world’s oceans and are characterized by their flattened body made up of five or more arms. Most of the more than 2000 species of starfish in the world feed on other animals such as crustaceans or mollusks.
- Echinoidea. Also known as “sea urchins”, they are characterized by having a round body and short spines that can be poisonous. They live on rocks or corals and feed on algae and other animals such as sponges.
- Ophiuroidea. Also known as “starfish”, they are characterized by having a flattened body and five very elongated and thin arms (which gives them a similar appearance to starfish). They usually live in corals and feed on crustaceans, mollusks, and fish.
- Holothuroidea. Also known as “sea cucumbers”, they are characterized by their elongated shape with bilateral symmetry and their mouth with tentacles. There are multiple species of sea cucumbers that have different sizes, almost all of them inhabit corals and feed on algae.
Examples of echinoderms
Sea lilies
- Davidaster rubiginosus
- Endoxocrinus parrae
- Elegant feather star
- Himerometra robustipinna
- Lamprometra palmata
- Celtic leptometra
- Ptilometra australis
- Stephanometrist indicates
Sea stars
| Asterias forbesi | Forcipulatide | Rainbow star |
| Crown of thorns | Goniasteridae | Pearl star |
| Sand star | Leiaster leachi | Pacific blood star |
| Captain star | Mithrodia fisheri | Oreasteridae |
| Blue sea star | Henricia del norte | Pentagonaster |
| Pink star | Nardoa galatheae | Spinuloside |
| Florida Starfish | Valvatida |
Ofiuras
| Ophiocoma erinaceus | Ophioderma | Brittle Crack Star |
| Amphipholis | Ophiurida | Brittle black star |
| Fine-spined ophiura | Ophiothrix spiculata | Brittle long-armed star |
| Amphiura arcystata | Ophioderma longicauda | Ophionereis annulata |
| Dwarf brittle star | Ophioderma panamensis | Ophiopholis kennerlyi |
| Ophioplocus esmarki |
Sea urchins
| Diadematoid | Black sea urchin | Green hedgehog |
| Sea chestnut | Headband hedgehog | Helmet hedgehog |
| Chondrocidaris gigantea | Fire hedgehog | Heart hedgehog |
| Sand dollars or uneven hedgehogs | Parson’s hat sea urchin | Long-spined sea urchin |
| Echinometridae | Pencil tip hedgehogs | Pseudoboletia indiana |
| Toxopneustidae |
Sea cucumbers
| Actinopyga | Stichopus | Chocolate chip sea cucumber |
| Black sea cucumber | Warty sea cucumber | Leptosynapta tenuis |
| Bohadschia Paradoxa | California Sea Cucumber | Sea cucumber snake |
| Holothuria cinerascens | Pineapple sea cucumber | Sclerodactylidae |
| Holothuria pervicax | Psolidae |