Life Cycle of a Jellyfish Jellyfish are probably some of the most unusual and mysterious creatures that you'll ever encounter. With their gelatinous bodies and dangling tentacles, they look more like something from a horror movie than a real animal. But if you can get past the weirdness -- and the fact that getting too close to one results in a nasty sting -- you'll discover that jellyfish are pretty fascinating. They've been around for more than 650 million years, and there are thousands of different species, with more species discovered all of the time. This lesson will summarize the life cycle of a jellyfish. Created by Jessica Brown

5 Phases Medua Planula Larva Polyp Strobilia Ephyra The most recognized image of a jellyfish is that of the adult jellyfish, with its bell-shaped body and long tentacles. But this image is just one of several stages in the life cycle of a jellyfish. Jellyfish progress through a number of forms: The medua, the planula larva, the polyp, the strobilia and the Ephyra.

Medua Also known as the mobile phase Typical jellyfish An adult jellyfish is a medua (plural: medusae), named after Medusa, the mythological creature with snakes for hair who could turn humans to stone with a glance. After the male releases its sperm through its orifice into the water, the sperm swim into the female's orifice and fertilize the eggs..

Planula Larva Tiny oval structure Outer layer is lined with minute hairs called cilia Cilia propel the planula through the water Short lived stage Planula Larva After the fertilized eggs have undergone embryonic development, they hatch and the free-swimming planula that emerge then leave the female's mouth or brood pouch and set out on their own. The planula larva is a short-lived stage in the jellyfish's life cycle. A planula is a tiny oval structure whose outer layer is lined with minute hairs called cilia. The cilia beat together to propel the planula through the water, but the motion of the cilia does not carry the planula far, instead ocean currents are responsible for transporting planula long distances. The planula floats for a few days at the surface of the sea. It then drops downward to settle on a solid substrate where it attaches itself and begins its development into a polyp.

Polyp Develops after the planula larva attaches itself to a hard surface Stationary stage Feeds by drawing food into its mouth This polyp stage in the jellyfish life cycle is a sessile stage, so called because the polyp is stationary and remains attached to a single spot on the sea floor. A polyp is cylindrical and stalk-like in form. At its base is a disc that adheres to the substrate and its top is a mouth opening surrounded by small tentacles. The polyp feeds by drawing food into its mouth. It grows and begins to bud new polyps from its trunk. As it does, the polyp develops into what is called a polyp hydroid colony or strobilia.

Strobilia Still stationary at this stage Asexual Reproduces by budding off new ephyra. Members of the polyp colony or strobilia are linked together by feeding tubes. The entire colony, like the originating polyp, is sessile. The strobilia can grow for several years. When polyps within the colony reach an adequate size, they are ready to begin the next stage in the jellyfish life cycle and are budded off into ephyra. This is an asexual phase.

Ephyra Tiny baby jellyfish Asexual Becomes the adult (medua) form of the jellyfish When the strobilia is ready to transform, the stalk portion of its polyps begin to develop horizontal grooves. These grooves continue to deepen until the polyp resembles a stack of saucers. The topmost groove matures the fastest and eventually buds off as a tiny baby jellyfish also known as an ephyra. The budding process by which polyps release ephyra is asexual. The ephyra grow in size and become the adult (medua) form of jellyfish.

Summary The lifespan of a Jellyfish typically range from a few hours to several months. The life span and maximum size of each species is unique. One unusual species is reported to live as long as 30 years and another species, is said to be effectively immortal because of its ability to transform between medua and polyp, thereby escaping death. Most of the large coastal jellyfish live about 2 to 6 months, during which they grow from a millimeter or two to many centimeters in diameter. They feed continuously and grow to adult size fairly rapidly. After reaching adult size jellyfish spawn daily if there is enough food in the ecosystem.