Simon Marweyi
Jan 31
With reference to obelia species, describe the life cycle in the class hydrozoa?
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Jan 31
The life cycle of Obelia species, which belong to the class Hydrozoa, involves both asexual and sexual reproduction.
1. Polyp Stage: The life cycle begins with a tiny, tubular polyp. The polyp attaches itself to a substrate, such as rocks or shells, using a basal disc. It has a cylindrical body with a mouth surrounded by tentacles. The polyp feeds on small organisms and plankton using its tentacles. It also reproduces asexually by budding. The buds grow into new polyps, forming a colony connected by a network of tubes called the coenosarc.
2. Medusa Stage: Under certain conditions, the polyps in the colony undergo a process called strobilation. Strobilation involves the development of specialized reproductive structures called medusae. The medusae are bell-shaped and free-swimming, resembling jellyfish. They are released from the polyp colony and enter the water column.
3. Sexual Reproduction: The medusae are dioecious, meaning there are separate male and female individuals. They produce eggs and sperm in their gonads. Fertilization occurs externally when the eggs and sperm are released into the water. The fertilized eggs develop into planula larvae.
4. Planula Larvae: The planula larvae are ciliated and swim freely in the water. They eventually settle on a substrate and undergo metamorphosis, transforming into polyps. This completes the life cycle, as the polyps grow and form new colonies.
It is important to note that the life cycle of Obelia species can vary slightly depending on the specific species and environmental conditions. However, the general pattern of alternating between polyp and medusa stages, with a combination of asexual and sexual reproduction, is characteristic of the class Hydrozoa.
1. Polyp Stage: The life cycle begins with a tiny, tubular polyp. The polyp attaches itself to a substrate, such as rocks or shells, using a basal disc. It has a cylindrical body with a mouth surrounded by tentacles. The polyp feeds on small organisms and plankton using its tentacles. It also reproduces asexually by budding. The buds grow into new polyps, forming a colony connected by a network of tubes called the coenosarc.
2. Medusa Stage: Under certain conditions, the polyps in the colony undergo a process called strobilation. Strobilation involves the development of specialized reproductive structures called medusae. The medusae are bell-shaped and free-swimming, resembling jellyfish. They are released from the polyp colony and enter the water column.
3. Sexual Reproduction: The medusae are dioecious, meaning there are separate male and female individuals. They produce eggs and sperm in their gonads. Fertilization occurs externally when the eggs and sperm are released into the water. The fertilized eggs develop into planula larvae.
4. Planula Larvae: The planula larvae are ciliated and swim freely in the water. They eventually settle on a substrate and undergo metamorphosis, transforming into polyps. This completes the life cycle, as the polyps grow and form new colonies.
It is important to note that the life cycle of Obelia species can vary slightly depending on the specific species and environmental conditions. However, the general pattern of alternating between polyp and medusa stages, with a combination of asexual and sexual reproduction, is characteristic of the class Hydrozoa.
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