What is the life cycle of a jellyfish? Jellyfish life cycle. Jellyfish have a stalked polyp phase, when they are attached to coastal reefs, and a jellyfish medusa phase, when they float among the plankton.
The medusa is the reproductive stage; their eggs are fertilised internally and develop into free-swimming planula larvae. Is a jellyfish a hermaphrodite? Jellyfish are usually either male or female with occasional hermaphrodites. In most cases, adults release sperm and eggs into the surrounding water, where the unprotected eggs are fertilized and develop into larvae. Are Jellyfish polyps or Medusa?
A polyp is the form that attaches to a surface, while a medusa is the form that is free-floating; a species of cnidarian may take each form in a different phase of its life.
The medusa form predominates in the classes Scyphozoa the common, colourful, large jellyfish and Cubozoa. Are sexes separate in Coelenterata? The sexes are separate and fertilisation may occur in the sea or inside the body of the female. The zygote becomes a ciliated planula, swimming in the plankton. It eventually settles and develops into a new anemone.
Do all cnidarians have nematocysts? All Cnidarians have tentacles with stinging cells in their tips which are used to capture and subdue prey. In fact, the phylum name "Cnidarian" literally means "stinging creature. The nematocyst is a coiled thread-like stinger. Corals are found primarily in shallow tropical waters, but a few grow in deep cold ocean waters. Small anemone-like cnidarians like Hydra sp.
Cnidarians range in size from tiny animals no bigger than a pinhead to graceful giants with trailing tentacles several meters long. Some animals that look similar to cnidarians are actually not part of the same phylum. An example of this is a type of jelly called a ctenophore Fig. Ctenophores were removed from the phylum Cnidaria and placed in a new phylum called Ctenophora pronounced ti-NOF-or-uh. Although both ctenophores and cnidarians have similar bodies with thin tissue layers enclosing a middle layer of jellylike material, scientists now group them separately.
These comb rows, called ctenes ctene meaning comb is how the ctenophores get their common name of comb jellies.
In the phylum Porifera we saw a body formed of aggregated cells with no organization into tissue layers or organs. Cnidarians have a slightly more organized body plan, and have tissues, but no organs. Most cnidarians have two tissue layers. The outer layer, the ectoderm , has cells that aid in capturing food and cells that secrete mucus. The inner layer, the endoderm , has cells that produce digestive enzymes and break up food particles.
The jellylike material between the two layers is called the mesoglea. All of these body layers surround a central cavity called the gastrovascular cavity , which extends into the hollow tentacles Fig.
Figure 3. The body plans cnidarians generally have radial symmetry Fig. Because the tentacles of corals, jellyfish, and sea anemones have this radial structure, they can sting and capture food coming from any direction. Many cnidarians take two main structural forms during their life cycles, a polyp form and a medusa form. The polyp form has a body shaped like a hollow cylinder or a bag that opens and closes at the top Fig.
Tentacles form a ring around a small mouth at the top of the bag. The mouth leads to a central body cavity, the gastrovascular cavity Fig. Polyps attach to hard surfaces with their mouths up. Because they are sessile organisms, they can only capture food that touches their tentacles. Their mesoglea layer is very thin. Corals and sea anemones are polyps. Most of these animals are small, but a few sea anemones can grow as large as 1 meter in diameter.
The second structural form that cnidarians have is called the medusa form. Medusa bodies are shaped like an umbrella with the mouth and tentacles hanging down in the water. The mouth leads upward into the gastrovascular cavity. Medusae plural; the singular form is medusa are not sessile, but rather are motile, meaning that they swim freely in the ocean Fig. Their mesoglea is thick and makes up most of their bulk. Jellyfish are medusae. Medusae come in many sizes ranging from small 2.
In many ways polyps and medusae are really the same basic body plan, except each is upside down compared to the other. Some cnidarians go through both a polyp and medusa phase in their life cycle. However, one or the other is the dominant phase in different species. It may look like a plant, but it's not. Sea anemones are a group of water -dwelling, predatory animals in the phylum Cnidaria.
A sea anemone is a polyp attached at the bottom to the surface beneath it. They can have anywhere from a few tens of tentacles to a few hundred tentacles. And they eat small fish and shrimp. Cnidarians are invertebrates such as jellyfish and corals. They belong to the phylum Cnidaria.
All cnidarians are aquatic. Most of them live in the ocean. Cnidarians are a little more complex than sponges. They have radial symmetry and tissues. There are more than 10, cnidarianspecies. They are very diverse, as shown in Figure below. All cnidarians have something in common.
A nematocyst is a long, thin, coiled stinger. It has a barb that may inject poison. These tiny poison "darts" are propelled out of special cells.
They are used to attack prey or defend against predators. Cnidarian Nematocyst. A cnidarian nematocyst is like a poison dart. It is ejected from a specialized cell. There are two basic body plans in cnidarians. They are called the polyp and medusa. Both are shown in Figure below. In the class Anthozoa, comprising the sea anemones and corals, the individual is always a polyp; in the class Hydrozoa, however, the individual may be either a polyp or a medusa, with most species undergoing a life cycle with both a polyp stage and a medusa stage.
Jellyfish have a stalked polyp phase, when they are attached to coastal reefs, and a jellyfish medusa phase, when they float among the plankton. The medusa is the reproductive stage; their eggs are fertilised internally and develop into free-swimming planula larvae. Polyp, in zoology, one of two principal body forms occurring in members of the animal phylum Cnidaria.
The polyp may be solitary, as in the sea anemone, or colonial, as in coral, and is sessile attached to a surface. Asexual Reproduction Often a polyp produced by sexual reproduction initiates growth of a colony asexually by budding.
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