# Moon Jellyfish (*Aurelia aurita*)

> The moon jellyfish (Aurelia aurita) is a translucent pulsing disc common in harbours worldwide, harmless to most swimmers. Bell diameter reaches 40 cm and the species is Least Concern.

- **Category:** Invertebrate
- **Conservation status (IUCN):** Least Concern
- **Range:** Coastal waters nearly worldwide.
- **Canonical page:** https://globalanimalguide.org/animals/moon-jellyfish/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Cnidaria
- **Class:** Scyphozoa
- **Order:** Semaeostomeae
- **Family:** Ulmaridae
- **Genus:** Aurelia

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Aurelia aurita |
| Diet | Carnivore (plankton) |
| Habitat | Coastal seas and harbours |
| Lifespan | 1–2 years |
| Weight | 0.1–0.5 kg |
| Top speed | up to 3 km/h |
| Conservation status | Least Concern (IUCN) |

## Four rings in a glass bell

Transparent bells show four horseshoe gonads. Short fine tentacles carry mild stinging cells. Rhythmic pulsation drives slow cruising in weak currents.

## Plankton and mollusc larvae

Cilia on oral arms move food to the mouth. They thrive in nutrient-rich harbours where zooplankton blooms.

## Coastal seas nearly worldwide

Harbours, bays, and shelf seas in temperate and tropical waters. Aurelia aurita is a complex of similar species globally.

## Bloom and bust cycles

Least Concern and often superabundant. Warm water, aquaculture nutrients, and reduced predators trigger spectacular blooms that clog power plant intakes.

## Frequently asked questions

### Are moon jellyfish dangerous?

Stings are mild for most people — a tingle rather than the medical emergency of box jellyfish.

### What are the pink shapes inside the bell?

Horseshoe-shaped gonads — reproductive organs visible through the transparent tissue.

### Why do moon jellyfish bloom?

Nutrient runoff, warming water, and fewer predators can trigger huge seasonal swarms.

### Do moon jellyfish have brains?

They have a diffuse nerve net — enough to pulse and orient but not for complex thought.

### Where are moon jellyfish found?

Coastal waters worldwide, especially harbours and sheltered bays.

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Source: Global Animal Guide (https://globalanimalguide.org/animals/moon-jellyfish/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.