What is a medusa in cnidarians?

What is a medusa in cnidarians?

medusa, in zoology, one of two principal body types occurring in members of the invertebrate animal phylum Cnidaria. It is the typical form of the jellyfish. The medusoid body is bell- or umbrella-shaped. Hanging downward from the centre is a stalklike structure, the manubrium, bearing the mouth at its tip.

What are 4 main characteristics of Cnidaria?

The five main characteristics of cnidarians are:

  • Radial symmetry.
  • Diploblastic animals.
  • Tissue level of organisation.
  • Presence of cnidoblasts with stinging nematocysts on the tentacles.
  • Polymorphism and have two body forms, i.e. polyp and medusa.

Which animal is a cnidarian?

cnidarian, also called coelenterate, any member of the phylum Cnidaria (Coelenterata), a group made up of more than 9,000 living species. Mostly marine animals, the cnidarians include the corals, hydras, jellyfish, Portuguese men-of-war, sea anemones, sea pens, sea whips, and sea fans.

What is polyp and medusa in Cnidaria?

There are two basic cnidarian body shapes: a polyp form, which is attached to a surface; and an upside-down free-floating form called a medusa. Some cnidarians change form at different phases of their life cycle, while others remain in one form for their entire life.

Which cnidarian is pictured in the medusa form?

> Another hydrozoan, the spine-chilling Portuguese Man of War, with tentacles that can dangle down to as far as 165 feet, lives its life mostly in the medusa form. >Scyphozoans include the animals referred to as true jellyfish, such as the animal pictured.

What is the effect of the poison produced by cnidarians?

What is the effect of the poison produced by cnidarians on their prey? The poison paralyzes the prey of the cnidarian.

What is a Cnidaria known for?

Cnidaria (/nɪˈdɛəriə, naɪ-/) is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter. Their distinguishing feature is cnidocytes, specialized cells that they use mainly for capturing prey.

How does the medusa feed?

The medusae feed using tentacles to bring prey to the mouth. The tentacles contain nematocysts, or cells that sting the prey and are also used for protection. Medusae swim via jet propulsion (pulsing of the bell). Phialidium is an example of a hydroid medusa.

What are cnidarian characteristics?

What are the Characteristics of Cnidarians?

  • They are characterized by the presence of stinging cells called Cnidoblast and a cavity called coelenterates, justifying the name Cnidaria or Coelenterata.
  • They are exclusively aquatic and marine.
  • They are radially symmetrical and diploblastic animals.

How do you identify a cnidarian?

The Cnidaria display two basic structural types: 1) the sessile polyp, that is more or less cylindrical and has the mouth at the free distal end, with a thin mesogloea; 2) the free swimming medusa, that is saucer- or bell-shaped, with the convex surface upward and with the mouth and surrounding tentacles at the under …

How rare are cnidarian medusae?

Fossils of cnidarian medusae are extremely rare, although reports of fossil “medusoids,” most of which do not represent medusae, are rather common. Our previous inability to distinguish these fossils has hampered attempts to investigate patterns and processes within the medusozoan fossil record.

What is the mesoglea of a cnidarian?

The mesoglea layer of the medusa body wall is thick and jelly-like. Some cnidarians only exhibit the medusa form throughout their life while others first pass through other phases before maturing into the medusa form. The medusa form is most commonly associated with adult jellyfish.

What is the Medusa of a squid?

The medusa form is a free-swimming structure which consists of an umbrella-shaped body (called a bell), a fringe of tentacles that hang from the edge of the bell, a mouth opening located on the underside of the bell, and a gastrovascular cavity.

How old is Cnidaria?

Cnidaria. However, molecular clock analysis of mitochondrial genes suggests a much older age for the crown group of cnidarians, estimated around 741 million years ago, almost 200 million years before the Cambrian period as well as any fossils.

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