Phylum Coelenterata, also known as Cnidaria, is a gathering of sea-going, or marine, creatures and a member of the Animal kingdom. They are generally viewed as attached to the stones at the lower part of the ocean. These are the multicellular and least difficult gathering of invertebrate creatures, found in provinces or singularly.
Coelenterates exist in two main body forms. The polyp is cylindrical and sessile (e.g., Hydra, Sea anemone) , while the medusa is umbrella shaped and free swimming (e.g., Jellyfish). In some species, alternation of generations occurs between the polyp and medusa forms.
Characteristics of Coelenterata
Characteristics of Coelenterata are given below:
- These are generally amphibious or marine natural surroundings creatures.
- These species show a tissue-level association.
- The mouth is encased by slight and short appendages.
- They are diploblastic creatures, in which the body is comprised of two layers of cells: Ectoderm (One layer makes up the cells outside the body) and Endoderm (different structures of the inward coating of the body).
- They have cavities in their body.
- The body is radially balanced.
- The absorption is both intracellular and extracellular.
- The sensory system and the circulatory framework are absent.
- They discharge and breathe through straightforward dissemination.
- The method of generation is agamic, which is through sprouting.
- The sexual method of propagation is seen exclusively in a couple of Coelenterata.
Classification of Coelenterata
Coelenterates possess a central body cavity called the coelenteron, which functions in digestion and circulation. A unique feature of this group is the presence of stinging cells called cnidocytes, which help in capturing prey and defence.
Coelenterates are ordered into five unique classes:
1. Anthozoa
- They are tracked down only in the marine climate.
- Mesoglea contains stringy connective tissues and amoeboid cells.
- Medusa is absent.
- Example: Metridium, Xenia.
2. Scyphozoa
- They are tracked down only in the marine climate.
- Medusa is prevailing and umbrella-moulded.
- Polyps are absent.
- Mesoglea is a cell.
- Example: Aurelia aurita, Rhizostoma.
3. Staurozoa
- Also known as Stalked jellyfish.
- They are mostly sessile medusae and show Radial symmetry.
- Possess cnidocytes (stinging cells) on tentacles.
- Example: Lucernaria and Haliclystus.
4. Cubozoa
- Also known as Box jellyfish.
- Body is cube-shaped with tentacles.
- Tentacles possess strong stinging cells (nematocysts).
- Example: Chironex (box jellyfish)
5. Hydrozoa
- These are, for the most part, marine species, tracked down only in freshwater.
- Few are found in settlements, and few are found singularly.
- Abiogenetic Polyps are the predominant structure.
- Mesoglea is acellular.
- Example: Hydra, Obelia.