The facts of (jellyfish) life

Jellyfish lifecycle
The medusa form of jellyfish (with its bell-shaped body and long tentacles) is just one of several stages in the jellyfish life cycle. Jellyfish progress through a number of other forms.

Thanks to a recent intern project, the lagoon jelly area in our Tropical Pacific exhibit now features a small ephyra bowl to give Aquarium visitors a glimpse of another phase of the jellyfish life cycle. Ephyra are the free-swimming jelly stage that comes before full-grown medusa.

Jellyfish reproduce both sexually and asexually. One generation (the medusa) reproduces sexually and the next generation (the polyp) reproduces asexually.

Moon jelly (Aurelia aurita) males in their medusa form, which can be seen in the Ring of Life exhibit, release sperm trails that are taken up orally by moon jelly females and fertilized internally. Lagoon jelly (Mastigias papua) medusas, on display in Ocean Oddities, spawn directly into the water. For both species, fertilized eggs develop into a multi-cellular planula and then into polyps that live on the sea floor.

At the polyp stage, jellies resemble tiny anemones and reproduce asexually by strobilation. When a polyp strobilates—segmenting its body to reproduce—it releases tiny ephyra into the water. Within a few weeks, a bell appears and the ephyra are considered medusa, starting the whole process over again!

How small are the ephyra? They’re tiny! About the size of this circle.

Go see them for yourself in the Tropical Pacific exhibit on your next trip to the Seattle Aquarium.

Please note: The ephyra bowl may periodically be empty as the population of ephyra fluctuates.

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