Echinodermata: Definition, Characteristics, Classification, Exampales, Facts

Definition Of Echinodermata

Echinoderms in the phylum Echinodermata are marine animals that consist of starfish, sea urchins, sand dollars, and so on up to sea cucumbers. The main features include; radial symmetry, a calcareous endoskeleton, and a water vascular system which is peculiar to this phylum and plays an important role in movement, feeding and at ts in respiration.

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Hence, echinoderms are an important element of the Southern Ocean and marine ecosystems in general, because they perform functions in terms of benthic environments. , they play a role in the organisation of space in the marine environment in biogeochemical processes. Through feeding on algae, predation of other invertebrates bioturbation of the sea bed, echinoderms are major contributors to the health and balance of the sea habitats, proving therefore to be very important in the support of oceanic diversity.

What are Echinoderms?

Echinoderms, also known and referred to as the marine invertebrate members of the phylum Echinodermaincludeudes such animals as starfish, sea urchins, and sand dollars as well as sea cucumbers. They are characterised by radial symmetry in most species with five arms, coverage of small plates or ossicles on the skin, and the water vascular system that helps it in locomotion, feeding, and respiration. Another characteristic that has been observed in echinoderms is regeneration where the organisms regenerate their lost appendages. These relatives of humans are characterised by their abundant presence in the arthropod phylum, which belonged to the Cambrian period, over 500 million years ago. This means throughout our world, echinoderms have had sufficient prehistoric background to spread out into a variety of sea zones, and are an essential part of the marine ecosystem.

Characteristics Of Echinoderms

Radial Symmetry

Today, echinoderms are marine animals that have radial symmetry, usually pentameral. This facilitates equal distribution of the formations of sensory and feeding organs which enable interaction with the environment from all sides.

Endoskeleton Composition

The endoskeleton present in the body contains the plates of calcareous ossicles majorly constituted of calcium carbonate. These ossicles serve to give rigidity and at the same time flexibility for the support of the body in its various forms.

Water Vascular System

The water vascular system is made of fluid-filled canals which help the animal in its locomotive, feeding and respiratory mechanisms. Hydraulic pressure enables it to move using tube foot, and also in handling food.

Pedicellariae And Spines

Among the calcareous plates on the surface of Echinoderms, there are pedicellariae, spinner-like-like organs and spines. They are involved in defensand and, mopping when constructed with spines and may also be an apparatus for trapping foods.

Regeneration Abilities

Echinoderms are known to be animals with excellent regeneration capacities, which means they are capable of regeneration of the lost body appendages. Regeneration is vital for survival and recuperation after an attack or an injury among other functions in organism survival.

Types Of Echinoderms

Class Asteroidea (Starfish)

Sea stars, which are also called starfish, are marine animals characterized by their hard body shape with five points a star in most cases but more in others. The body structure is composed of a central disc and the terms, which are covered with tube feet which are used in motility in feeding. The starfish are part of many ocean food chains as predators and carnivores.

Class Ophiuroidea (Brittle Stars)

Brittle star possesses the elongated flexible arms, unlike the central disk. They locomote by crawling with their arms rather than er flexing tube feet. Generally, brittle stars are detritus feeders while they feed on detritus and small organisms.

Class Echinoidea (Sea Urchins and Sand Dollars)

Sea urchins intertwine in a spherical form with long spines, on the other hand, sand dollars are flat and circular shaped. Both have a tough outer covering known as the test. The butterfly urchin browses on algae and thus plays a role in curtailing the growth of algae and the sand dollar feeds on particles in the sediment.

Class Holothuroidea (Sea Cucumbers)

Sea cucumbers are characterized by elongated soft-bodied animals that are gratefully located on the bottom of the sea. It is believed that they have a significant function in recycling nutrients, as well as oxidation of organic matter/turning over the sediment of the sea floor. This, is, for instance, some species can't eject their bodily organs as a sign defence mechanism.

Class Crinoidea (Feather Stars and Sea Lilies)

Feathstarstar and sea lilies have arms branching off a central disc with the arms used for filter-feeding where the crests capture particles of food from the water. In sea lilies, the body usually has a stalk which fixes it to the bottom while the feather stars can be moved from place to place. They are primitive members of cohort Echinodermata with the show first appearance in the Paleozoic period.

Echinoderm Anatomy

External Feature

The exoskeleton or skin of the echinoderms is generally spiny or leathery having pedicellariae – like small pincers – and tube feet developing from the water vascular system. Their body plan is typically radial, with wifive-foldold symmetry aa and transverse sectlly pentagonal; and they are provided with an endoskeleton formed of calcareous plates or ossicles.

Internal Structures

Water Vascular System

This system in echinoderms is made up of a system of canals that are filled with fluid. Some of the structures are madreporite, the stone canal, the ring canal, the radial canals and the tube feet. The water vascular system helps movement, feeding as well as in respiratory operations by the pressure of the water.

Digestive System

It has a head on one end referred to as the oral surface antail-likelike structure known as the aboral surface with an anus. In digestion,on the stomach may reach the arms, especially starfish fish, whereby it may evaporate.

Nervous System

The percentages of the echinoderms’ nervous system control are disadvantageous because they are devoid of a proper brain. This is represented by a nerve ring surrounding the mouth, and 4 radial nerves running to the arms. This organization of the two organs enables them to plan how to move as well as how to about the stimuli within the environment.

Respiratory System

Gills or dermal branchiae are in some species whereas others have tube feet and in some species respiratory trees like in holothurians. These systems are used for respiration to exchange gases with the water in which the organism lives.

Circulatory System

Like many other invertebrates, echinoderms’ circulatory system is not well developed and is considered to be the hemal system. With its system of sinuses and channels, it serves to deliver nutrients and disburse waste products. This system also has an important function related to the internal transport of animals even though it is commonly associated with the movement of the creatures.

Echinoderm Reproduction

Reproductive Strategies

Reproduction or breeding is another important aspect of Echinoderms; most of Echinoderm’s species reproduce sexually, though there are some hermaphrodites, species produce eggs and sperms which are liberated in seawater to facilitate external fertilization. Particularly, some of these created species are reproducing through asexual means through factors like fragmentation and regeneration, whereby a clearance reproduces through the act of breaking a part of his which forms another new subject.

Larval Development

The echinoderms go through a stage called metamorphosis before they can transform to the adult stage which is characterized by the larvae. Echinoderm larvae, for instance, as the bipinnaria and brachiolaria of the starfish, are bilaterally symmetrical and free-living mobile via cilia in the water. During their ontogeny, they transform, increasing the radial symmetry which is characteristic of the adult echinoderms. This pre-imaginal stage which is most likely a result of evolution is very important in the dispersal and establishment of new habitats.

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