Cnidaria
All cnidarians can regenerate, allowing them to recover from injury and to reproduce asexually. Medusae have limited ability to regenerate, but polyps can do so from small pieces or even collections of separated cells. This enables corals to recover even after apparently being destroyed by predators. In the Cnidaria sexual reproduction often involves a complex life cycle with both polyp and medusa stages. For example in Scyphozoa (jellyfish) and Cubozoa (box jellies) a larva swims until it finds a good site, and then becomes apolyp. This grows normally but then absorbs its tentacles and splits horizontally into a series of disks that become juvenile medusae, a process called strobilation. The juveniles swim off and slowly grow to maturity, while the polyp re-grows and may continue strobilation periodically. The adults have gonads in the gastrodermis, and these release ova and sperm into the water in the breeding season.
|
Atlantic Sea Nettle
In their polyp form, Atlantic Sea Nettle reproduces asexually. This is done through a variety of ways: strobilation, cyst production, and by changing polyp position through the use of stolons. Medusae are able to reproduce sexually. Females catch the sperm released into the water from the mouths of the males. The eggs, which are also held in the mouth,become fertilized, and remain attached to the female's oral arms. As the fertilized eggs develop, they grow into planula. These planula have a flattened, bean shape. Once the polyps develop fully into flower-shaped progeny, they are released into the ocean where they settle, and begin
asexual reproduction. The polyp buds to produce identical copies of themselves, and eventually detach to be released into the ocean where it will undergo metamorphosis to the medusa stage. Fertilized eggs will remain attached to the female parent's oral arms. The eggs into planula on the arms. Once the polyps develop fully into flower-shaped progeny, they are released into the ocean where they settle.
Heliofungia Corals
Heliofungia corals can reproduce sexually or asexually. During sexual reproduction, eggs and sperm are released into the water, where the
fertilised egg develops into larvae. Within a fortnight, the larvae will settle on to hard substrate. Asexually Reproduced young coral, or acanthocauli, can develop from partly buried, damaged or dying parent tissue.Either way, the result is a vase-shaped polyp that gradually grows into a flattened disc, attached to the substrate via a stalk. The stalk of the mushroom eventually dissolves, and the coral becomes mobile. The newly mobile coral rests on the bottom where it will mature and reproduce.
Pacific Sea Nettle
The Pacific Sea Netttle is capable of both sexual reproduction in the medusa stage and asexual reproduction in the polyp stage. The life cycle of C. fuscescens begins when females catch sperm released by the males to fertilize the eggs she has produced and is holding in her mouth. These fertilized eggs remain attached to her oral arms, and there they grow into flat bean-shaped planula. Once they grow into flower-shaped polyps, they are released into the ocean where they attach themselves to a solid surface and undergo asexual reproduction. The polyp makes identical copies of itself this by means of budding, where the new polyp grows from its side. After the new polyp is fully formed, it too is released into the ocean and undergoes
metamorphosis as it grows, developing a bell, arms, and tentacles until it is a fully formed medusa.
metamorphosis as it grows, developing a bell, arms, and tentacles until it is a fully formed medusa.