How do jellyfish reproduce?

Jellyfish reproduction involves both sexual and asexual processes: the fertilization of eggs, the release of hatched larvae and the asexual cloning of these larvae to produce infant jellyfish. The life cycle of a jellyfish lasts only a few months, although the larval stage can last many years or decades.

The reproduction of jellyfish can be outlined in the following four phases:

1. Male jellyfish release a cloud of sperm cells from their mouths, through which female jellyfish swim. Fertilization takes place either in the female's brood pouch or stomach, depending on the species and where it carries its eggs.
2. Once the eggs have been fertilized and gestated within the mother, jellyfish larvae hatch and leave via her mouth. These larvae are known as "planula."
3. Settling on smooth rocks and other solid surfaces, the planula transform into polyps, often multiplying to form colonies before laying dormant to await optimal environmental conditions for their next stage of development.
4. After the dormant period, the polyps bud (or strobilate) to release many thousands of infant jellyfish into the same small area of the ocean. The vast quantity of this release helps to ensure optimal survival rate. These infant jellyfish are termed "ephyra," which take a few weeks to fully mature into adult (or "medusa") jellyfish.