Which fertilisation is seen in coelenterata ?

Question

Answer

External mostly. Polyp and medusa stage are found in it..

Answer

Fertilization is internal in some species like hydra etc...&external also with indirect development

Answer

External fertilization mostly.
Two sexual stages are found that is polyp and medusa.
They show alteration of generations i. e. polyp produce medusa asexually and medusa produce polyp sexually.
In hydra and adamsia polyp stage is present while in aurelia medusa stage is present.
True metagenesis is shown by Obelia.

Answer

Fertilization in Coelenterata

Coelenterata, also known as Cnidaria, is a phylum of aquatic animals that includes jellyfish, sea anemones, corals, and hydrozoans. These animals reproduce sexually, and their fertilization process varies depending on the specific class within the phylum. In general, fertilization in Coelenterata can occur either internally or externally.

1. Internal Fertilization:

Internal fertilization is a process in which the fusion of sperm and egg occurs within the female's body. This type of fertilization is relatively rare in Coelenterata, but it is observed in some members of the class Scyphozoa, specifically in the order Rhizostomeae. Rhizostomeae are large jellyfish that have a complex reproductive system. During mating, the male releases sperm into the water, which is then ingested by the female. The sperm is stored in the female's body until the eggs are ready for fertilization. When the eggs are released, they are fertilized by the stored sperm, and the development of the embryo begins.

2. External Fertilization:

External fertilization is the more common method of reproduction in Coelenterata. It involves the release of both sperm and eggs into the surrounding water, where fertilization occurs. This process is observed in various classes within the phylum, including Hydrozoa, Anthozoa, and some members of Scyphozoa.

- Hydrozoa: In hydrozoans, such as hydroids and Portuguese man o' war, the male and female reproductive cells are released into the water column. The sperm and eggs are often released simultaneously, increasing the chances of successful fertilization. Once fertilization occurs, the zygote develops into a planula larva, which eventually settles and develops into a polyp.

- Anthozoa: Anthozoans, which include sea anemones and corals, also reproduce externally. They release eggs and sperm into the water during spawning events. The fertilized eggs develop into planula larvae, which float in the water before settling on a suitable substrate and developing into a polyp.

- Scyphozoa: Most jellyfish species, belonging to the class Scyphozoa, reproduce through external fertilization. During their reproductive cycle, mature male jellyfish release sperm into the water, while mature females release eggs. The sperm and eggs combine in the water, and the fertilized eggs develop into larvae called planulae. These larvae swim freely in the water before attaching to a surface and developing into a polyp.

In conclusion, fertilization in Coelenterata can occur through both internal and external methods. While internal fertilization is less common and observed in some jellyfish species, the majority of Coelenterata species reproduce through external fertilization, where the sperm and eggs are released into the water for fertilization to occur.

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