This phenomenon is called rphism is very common in coelenterates and the class Hydrozoa provides the best example of polymorp. 10 Jul POLYMORPHISM IN COELENTERATES The presence of polymorphism in cnidarians is one of their characteristic features. It is defined as. In Hydrozoan coelenterates polymorphic tendency is well developed. The order Siphonophora organisms are exhibiting this tendency to a maximum extent.

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The “smell” of fluids from wounded prey makes the tentacles fold inwards and wipe the prey off into the mouth. Ecdysozoa Scalidophora Kinorhyncha mud dragons Priapulida penis worms.

According to this theory, a polymorphic coelenterate is supposed to be a colonial form in which various types of zooids have been aggregated to perform different functions. In medusae the tentacles round the edge of the bell are often short and most of the prey coelenterqtes is done by “oral arms”, which are extensions of the edge of the mouth and are often frilled and sometimes branched to increase their surface area.

Coelenterata: General Characters, Tissues and Corals | Metazoa

Polyp has a tubular body with a mouth surrounded by tentacles at one end. Among Hexacorallia, Antipatharia includes black corals like Antipathes. It has mouth at its apex. Invertebrate Zoology 7 ed. The endosymbiotic algae of many cnidarian species are very effective primary producersin other words converters of inorganic chemicals into organic ones that other organisms can use, and their coral hosts use these organic chemicals very efficiently.

Great widening of the body has doelenterates, especially along the oral surface. Other polyps such as Tubularia use columns of water-filled cells for support.


This improves respiration after feeding and allows these animals, which use ccoelenterates cavity as a hydrostatic skeletonto control the water pressure in the cavity without expelling undigested food.

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Canadian Coelentefates of Zoology. At the same time a rim is built up as a thecal wall around the polyp, lying at the top. They are filled with secreted gas.

The order Siphonophora organisms are exhibiting this tendency to a maximum extent. As per this thought polyp is considered to be persistent polyjorphism stage and medusa is the completely evolved coelenterate. Posted by Zoologists at Placozoa Trichoplax Cnidaria jellyfish and relatives. In Physalia the gonozooid shows branched stalk, bearing clusters of gonophores gonopalpon. If the body tilts in the wrong direction, the animal rights polymofphism by increasing the strength of the swimming movements on the side that is too low.

Stauromedusaealthough usually classified as jellyfish, are stalked, sessile animals that live in cool to Arctic waters. Cnidarians are distinguished from all other animals by having cnidocytes that fire harpoon like structures and are used mainly to capture prey. All these large and small nematocysts are enclosed within a single large epithelio-muscle cell. Then the island subsides very slowly, so slowly that the reef grows upward at about the same rate, naturally coelentsrates island becomes small, the channel between the reef and land widens and thus the fringing reef transforms into a barrier reef.

It is not a single structure but is made up of many strings of separate reefs joined to each other at the bottom and thus forms a very big structure which extends along the polymorphisn eastern coast of Australia for over kilometers.

Polymorphism In Coelenterates | Navodita George Maurice –

Gastro vascular cavity is divided into compartments by complete or incomplete septa or mesenteries. This kind of nematocysts is useful in attachment and anchorage. The body wall of all the coelenterates contains special defensive structures called as stinging cells or nematocysts. Cnidarians’ activities are coordinated by a decentralized nerve coslenterates and simple receptors. Siphonophora show the highest degree of polymorphism which is not polymorphissm anywhere else in the animal kingdom.


The polymorphism is essentially a phenomenon of division of labour in which different functions are performed by the different members or zooids of the colony, viz.

However, they do have integrative areas of neural tissue that could be considered some form of centralization. Anus is not found. Many cnidarian species produce colonies that are single organisms composed of medusa -like or polyp -like zooids, or both hence they are trimorphic. Jellyfish Phyllorhiza punctata Scyphozoa.

The following are various patters of polymorphism found in hydrozoa. Polyp and medusa are in fact homologous structures and from one another can easily be derived. In some species it also contains low concentrations of cnidocytes, which are used to subdue prey that is still struggling. In molecular phylogenetics analyses from onwards, important groups of developmental genes show the same variety in cnidarians as in chordates.

Pierre and Miquelon St. In Diphyes colonies are linear with one or more nectophores located at the apical end. Dactylozooid is defensive in function. This hydra like polyp gave rise to hydroid colony through asexual budding.

Siphonophore Physalia physalis Hydrozoa. Indigestible remains of prey are expelled through the mouth. Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top.

Gastrozooids catch the prey and digest it. Polyps are concerned with feeding, protection and asexual reproduction.