Prepared by : Nada H. Lubbad Phylum Cnidaria Prepared by : Nada H. Lubbad

General Characteristic : Metazoa ( true tissues ). Coelentrata , single cavity to the body ( enteron or gastrovascular cavity ) Radially symmetrical. Diploblastic: - Ectoderm ( dermis ) - Mesoglea ( non- living jelly - like structure ) - Endoderm ( Gasrodermis ) Possess a single opening that serve as a mouth and anus which surrounded by tentacles.

Life form: Feeding: Mostly marine. Few in fresh water. Solitary , colonial , sedentary , free- swimming. Feeding: Carnivores. Cnidarians use tentacles to capture prey and push them into their mouths. The mouth leads to gastrovascular cavity which function in digestion. Tentacles : It used for capture of prey and defense. Cnidocytes , specialized cells found on the surface of structure. Trigger , section found on the top of each Cnidocytes. When this area of cell is touched , a coiled thread is discharged. This causing the prey or predator to become unable to fight or escape.

Many Coelentrata exist in two body form – a polyp and medusa. Polyp Polymorphism: Many Coelentrata exist in two body form – a polyp and medusa. Polyp Medusa Tubular body Umbrella-shaped body Mouth directed upward Mouth directed downward Small amount of mesoglea Large amount of mesoglea sessile Motile – float freely in the water

Phylum Cnidaria is divided into 4 classes:

Class hydrozoa Hydra General features: Inhabitant of fresh water. Medusoid stage is absent. The hydroid stage is solitary and sedentary. Hydra is about 4-10 mm in length. It feeding on small crustaceans such as Daphina and other small animals. Symbiotic zoochlorellae live in the endodermal cells of H. viridis giving the animal its green coloration.

Reproduction: Asexual reproduction: by budding , the buds are usually connected to the body of the parent at the connection of its two lower thirds. 2. Sexual reproduction: Gonads, organs of sexual reproduction. Testes: appear as a conical swellings near the oral cone. Ovaries: they are formed about the middle of the body. Hydra is either : - Hermaphrodite (monoecious), developing both types of gonad in the same individual. - unisexual (dioecious), the sexes are separate.

Obelia Marine coelenterate. Dimorphic, exhibiting two different forms in life cycle ( Hydroid and Medusoid). - Hydroid form : colonial, sedentary . It reproduces asexually giving the Medusoid form. - Medusoid form: free- swimming. It reproduces sexually giving rise to hydroid form again.

Reproductive polyp ( Gonozooid ) Feeding polyp ( Gastrozooid )

Free- swimming larvae ( Planula )

Class scyphozoan (scyphomedusae) cup animal It includes the larger jellyfishes. Marine. The medusa is the predominant phase , the hydroid stage is reduced and included in the life – history only as a polypoid larva. Aurelia The sexes are separate. Scyphistoma : polyp form , stores food , multiplies asexually and produces a number of discs called ephyra by a strobilization process. Ephyra : a small larva medusa.

Class cubozoa ( cubomedusae ) They are known as box jellyfish, because in transverse section the bells appear to be square. They are effective predators and strong swimmers. Their nematocysts are especially potent, sometimes resulting in the death of human swimmers.

Class Anthozoa ( Actinozoa ) Flower animals Sea Anemones & corals It includes the sea anemones and reef-building corals. Entirely marine. Solitary or colonial . It exists only in the hydroid stage. It has an oral disc bearing hollow tentacles. The enteron is divided by mesenteries, and the entrance to the enteron is by a stomodaeum. The Anthozoa are divided into two subclasses: Octocorallia ( Alcyonaria) and Hexacorallia (zoantharia).