When you think of a jellyfish, the image of a translucent, bell-shaped creature with flowing tentacles likely comes to mind.

While this medusa phase is the most recognizable, it's just a brief stage in the jellyfish's incredible and complex life cycle.

Let’s dive into the remarkable journey of jellyfish, focusing on the Aurelia moon jelly for consistency!

1. Life Begins: The Egg

Just like humans, a jellyfish’s life begins with reproduction. At dusk or dawn, mature jellyfish, known as medusae, gather in large numbers to spawn, releasing eggs into the ocean. Spawning events are triggered by proximity, light, and food availability. Some species, like moon jellies, even protect fertilized eggs by attaching them to their arms until the next stage of life begins.

2. Jelly Babies: Planula Larva

The fertilized egg develops into a planula larva, a tiny, free-swimming organism covered in hair-like cilia that propel it through the water. The planula searches for a solid surface, such as the seabed or even another animal, to attach itself. Once settled, it transforms into the next phase of life.

3. The Long Childhood: Polyps

After attaching, the planula becomes a polyp, a small stalked creature with tentacles surrounding its mouth. In this stage, the jellyfish develops a digestive system and begins feeding. Polyps can survive for years, waiting for ideal conditions to progress. They closely resemble their relatives, like sea anemones, but unlike anemones, polyps continue evolving into later stages of life.

4. Budding Teenagers: Scyphistoma

When conditions are optimal, polyps reproduce asexually through a process called strobilation. The polyp elongates and segments into stacks of clones, each segment capable of becoming a new jellyfish. These segments, called scyphistoma, eventually separate and form individual organisms.

5. Finding Themselves: Ephyra

The released segments, now known as ephyra, are free-swimming juvenile jellyfish. Though small and undeveloped, they are equipped with basic muscles, nerves, and digestive systems. As they feed and grow, ephyrae begin to resemble their mature form, preparing for their next phase.

6. Frisky, Hungry Mature: Medusa

As the ephyra matures, it becomes a medusa, the mature jellyfish form most people recognize. The medusa’s primary purpose is reproduction. Jellies in this phase grow quickly, as larger size increases reproductive success. Depending on the species, some mature jellyfish gather in massive spawning blooms, while others live solitary lives in the deep sea, relying on longer lifespans to reproduce.

7. Death (But Not Really)

The medusa stage is short-lived, with most mature jellyfish surviving only a few months. As they age, their energy is directed toward reproduction, often at the expense of their immune systems. Older jellies are more vulnerable to infections, like bell rot, which is common in their final days.

Jellyfish are masters of survival, reproducing rapidly when conditions are ideal. Their ability to clone themselves, combined with their simple yet effective life cycle, makes them one of the ocean’s most resilient creatures!

The LIfe Cycle of Jellyfish

Video by Raspitomaru