Phylum Coelenterata

Introduction

A group of simple multicellular, specific marine or aquatic organisms is known as phylum Coelenterata. Here we will discuss the concept of Phylum Coelenterata along with the Classification of coelenterata, general characteristics of coelenterata and features of coelenterata.

This article will also help you understand the concept of Phylum Coelenterata, it’s classification and general characteristics and will also help in solving all your textbook questions.

What is Phylum Coelenterata?

Phylum Coelenterata is a group of specific marine or freshwater organisms and a member of the animal kingdom. They are a simple group of multicellular, invertebrate animals. It means phylum Coelenterata are cold-blooded animals with no backbone. They live in colonies or solitary. They can have two forms in one life. One form is polyp and the other is medusa. Polyp is an asexual phase and medusa is a sexual phase. By budding, polyp is converted into medusa. Medusa first converts into larva and then converts into polyp. Some coelenterate like Hydra have only one sexual phase in their life.

Phylum Coelenterata is a parazoa of the animal kingdom. Parazoa includes cellular level of organisation in animals. 

The term coelenterate comes from its central gastrovascular cavity called coelenterates. Coelenterates are also called cnidaria due to their cnidocytes cells which are stinging cells. The cell has Nematocyst which produces hypnotoxin. These cells are used for defence, offence, capturing of prey, locomotion etc. Coelenterata are carnivorous. They are of two types: fixed or sedentary and free-floating. They are radial symmetry which means you can cut it from between in equal parts. The phylum includes sea pens, comb jellies, coral animals, true jellies hydra etc. Corals have skeleton and jelly fishes do not have skeleton.

Important features of coelenterata

• These animals live in water

• These show more body design and differentiation of tissues

• These have body cavities but cannot be termed as true body cavities

• These are the first multicellular animals which exhibit tissue level organisation and division of labour

• The body wall has two layers which are ectoderm and endoderm held together by mesoglea (acellular layer)

• In the life cycle these animals show alternation of generation

Categorization of Coelenterata

Phylum Coelenterata has three classes which are as:

1. Class Anthozoa 
2. Class Hydrozoa
3. Class Scyphozoa

Class Anthozoa:-  Anthozoa includes cnidarians which have a polyp body plan. The medusa stage is not present in their life cycle. Examples include sea pens,  sea anemones and corals. There are almost 6,100 described species. This class has two types of animals: anemones and coral. Anemones do not have skeletons. On the other side, corals have skeletons. An example of Anemones is adamsia. Examples of corals are pennacula, gorgonian, corallium, meandrina. Pennacula is also known as the sea pen. Gorgonians are also known as sea fans. Corallium is also called red coral. This is the most expensive item on the market. Meandrina is also called brain coral. Corals are found in the sea bed. They can be sun-dried and can make a whole island.

Class Hydrozoa:- Hydrozoa  Class invertebrate member is called hydroid. Most hydroids live in marine environments, but from them, some have come and invaded the freshwater habitats. The Hydroids live in colonies or solitary. There are around 3,700 species that are known. Hydra is a freshwater polyp and does not have a canal system. It is cylindrical and has 4 to 25 tentacles. It is about 30mm. Obelia is also called sea fur because it looks like fur in the sea. This is both sexual and asexual. Physalia are found in the Atlantic and Indian oceans. Their surfaces are flat. They are also called Portuguese men o’ war. They are free-floating. They have neurotoxic, gas glands.

Class Scyphozoa:- Scyphozoa are a marine class of phylum Cnidaria. The species of Scyphozoa lives in two phases -the history phase,  the form of jellyfish or planktonic medusa, which are inhabitants of the warm summer months and the other is an inconspicuous which is longer-lived and a bottom-dwelling polyp. They seasonally give rise to new medusae. Aurelia is an example of Scyphozoa. It is also called jellyfish and moon jelly. It carries 98% water.

Conclusion

A group of marine or aquatic organisms is called Phylum Coelenterata. They are multicellular. They are also a simple group of invertebrate animals. Coelenterates are also called cnidaria due to their cnidocytes cells which are stinging cells.

Coelenterata are carnivorous. They are of two types: fixed or sedentary and free-floating. They are radial symmetry. A tissue-level organisation exhibits these species. The mouth is encircled by thin and short tentacles. There are cavities in the body.

Coelenterata is classified into three classes: Anthozoa, Hydrozoa, Scyphozoa. Anthozoa includes cnidarians which have a polyp body plan. Most hydroids live in marine environments. The species of Scyphozoa lives in two phases -the history phase,  the form of jellyfish or planktonic medusa, which are an inhabitant of the warm summer months and other is an inconspicuous which is longer-lived and a bottom-dwelling polyp.