Reproduction of coelenterates can be asexual or sexual. In many species there is alternation of sexual and asexual phases.
Asexual reproduction usually occurs by budding. In this case, shoots are formed in certain regions of the animal's body; each bud develops and gives rise to a new individual.
This new animal can hold together with the originator, forming colonies, or stand out and have an independent life.
Hydra presenting a bud, which will detach from the adult organism, will fall on the substrate and form a new individual.
In this case, male gametes (sperm) are released into the water and swim in search of female gametes (eggs). Depending on the species, the egg may also be released into the water or remain adhered to the body surface of the animal in which it was produced.
After fertilization of the egg, the formed zygote develops into an embryo. In some species, the embryo directly gives rise to a new parent-like organism. In others, the embryo gives rise to a moving larva, it swims, and settles somewhere, where it becomes a new individual similar to parents.
Asexual and sexual phase switching
In many coelenterate species, reproduction involves the alternation of one asexual phase with another sexual phase. We will highlight, for example, what happens between jellyfish.
In jellyfish reproduction, the phase sexual happens in the form of jellyfish, the most developed phase of the cycle; The asexual occurs in the form of polyp, which is reduced. Observe the scheme:
After sperm fertilize the egg, the zygote forms, which develops into an embryo. From the development of the embryo a larva is formed that will give rise to a small polyp.
The polyp grows and reproduces asexually; In this process your body forms several fragments that stand out from it. Each fragment can give rise to a young jellyfish, which develops into an adult individual.
Sexual reproduction of hydra. Note that the embryo initially develops in the female body; after a while he detaches himself from his mother and originates a new hydra.