Classification of invertebrate zoology(phylum coelenterata)

Phylum Coelenterata;

The term coelenterate derived from (Greek word koiles ; cavity and enteron ;intestine), and it was first coined by Leuckart  in 1847.

Features/Character of phylum coelenterate;

All the animals of phylum coelenterata or cnidaria having a body wall that consist of two layer of cells between which a jelly like substance, mesoglea is present. They are multicellular or metazoan animals. They are having aquatic mode of life, mostly is marine while of some them are fresh water forms like hydras. They are free swimming, solitary or colonial form in nature . They are having single gastrovascular cavity or coelenteron within their body, that communicate to exterior through the mouth. Their mouth is bear short and slender tentacles which are used to capture and ingest the food. They are having nematocyst that are used to paralyse the prey by injecting poision or hold the prey used for adhesion. Phylum coelenterata show the phenomenon of polymorphism. They are having exoskeleton and endoskeleton. In coelenterate the reproduction occur by two means; asexual reproduction take place by mean of budding, while  sexual reproduction take place by mean sperm and ova. However their eggs develop into the ciliated larva know as planula. Furthermore they show the process of alternation of generation of metagenesis for instance asexual polyp with sexual medusa.

Classification of phylum coelenterata;

The coelenterate are differentiated into the three classes;

Class 1. Hydrozoa;

The members that belong to this class are colonial in nature. Some of species exist as polyp that give rise by the process of budding to free or sessile medusa. The medusa consist of  velum and nerve ring. Here mesenteries are absent in polyp. The members of this class having solid tentacles, as well having phenomenon of polymorphism. They are having ectodermal reproductive cell which is directly discharge to the exterior. In these animals holoblastic cleavage take place, while their embryo is planula. This class has been differentiated into the four orders;

 Order 1. Actinulida
 Order 2. Siphonophorida
 Order 3. Trachylinida
It is further divided into the three suborders which is following;
Sub-order Trachymedusa, pteromedusa and Narcomedusa.
 Order 4. Hydroida;

The hydroid consist of one of the following suborders;

Such as Hydrocorallinae, Leptomedusae, Anthomedusae and Limnomedusae.

Class 2.Scyphozoa;

These animals can be differentiated from hydrozoans medusa by presence of notches, however these are eight in number in the margin of umbrella. They are said to be acraspedote medusa in contrast of craspedote medusa of hydrozoa. The scyphozoan are ranging from a few centimeter to one centimeter in diameter but in some cases it might be two meter in diameter along with tentacles that is 28m long. These are marine in habit and floating near the sea surface, while some of them are attached with the rocks and weeds. They show alternation of generation in their life history. They show cellular mesoglea. They are having ectodermal gonads but their sex cells discharge into the stomach. Mostly jellyfishes belong to this class. The scyphozoa is differentiated into one of the following orders;

 Order 1. Stauromedusida

 Order 2. Rhizostomida

 Order 3. Coronatida

 Order 4. Semaeostomida

 Order 5. Cubomedusida

Class 3. Anthozoa;

The anthozoa are colonial or solitary coelenterates having polyp stage without medusa. The polyp being have coelenteron that is divided into the  chambers through the mesenteries. If mesenteries are absent in that case there are eight branched tentacles are present. Mostly the anthozoa secrete the calcareous skeleton know as coral. They are having mesoglea that consist of connective tissue as well amoeboid cells. They are having endodermal gonads that is develop inside the mesenteries while their mature sex cell released into the coelenteron. They are having external fertilization, however their fertilized egg develop in to the planula larva. The anthozoa is differentiated into two sub-classes such as subclass Zoantharia and subclass Alcyonaria. The zoantharia consist of the following orders;

 Order 1. Actiniarida

 Order 2. Madreporarida/Scleractinida

 Order 3. Antipathida

 Order 4. Corallimorphida

 Order 5. Ceriantharida

 Order 6. Zoanthida

In Subclass Alcyonaria include one of the following orders;

Order 1. Alcyonacida

Order 2. Pennatulocida

Order 3. Gorgonocida