---
title: Upside-down Jellyfish (Cassiopea andromeda)
scientific_name: Cassiopea andromeda
common_name: Upside-down Jellyfish
taxon: Jellyfishes
published: 2023-12-27T22:47:25.631Z
updated: 2026-08-12T09:21:03.652Z
tags: Upside-down Jellyfish, Cassiopea andromeda, Jellyfishes, Red Sea, Marine Life, Diving
url: https://redseacreatures.com/taxon/invertebrate/stinging/jellyfishes/upside-down-jellyfish
---

# Upside-down Jellyfish (*Cassiopea andromeda*)

## Quick facts

- **Group:** Jellyfishes (*Scyphozoa*)
- **Size:** up to 30 cm across
- **Depth:** 0-10 m
- **Diet:** Omnivore
- **Activity:** Diurnal
- **Rarity:** Common
- **Habitat:** Sheltered shallow bays and mangrove flats, lying on the bottom
- **Reproduction:** Broadcast spawner, Budding, Gonochoric
- **Hazard:** Venomous

## How to recognise it

- lies on the bottom bell-down with the arms pointing up, like a flower
- branched frilly arms, blue-gray to olive with pale spots
- pulses gently in place rather than swimming anywhere
- bell up to 30 cm across

A jellyfish that lies on its back on the bottom of a shallow bay, bell down, frilly arms pointing at the sky, pulsing gently and going nowhere. Fields of them in ankle-deep water look like a bed of olive flowers.

The posture is agriculture. The tissue is packed with symbiotic algae, and the animal lies inverted to hold them in the sunlight for as long as the day lasts, living largely on the sugar they produce and topping it up with plankton caught in mucus. Where the water is clear and shallow, that is a better business than swimming.

It stings without touching. Swimmers over a bed of these report burning skin without contact, and the reason was only worked out in 2020: the animal releases little balls of stinging cells wrapped in mucus, self-propelled by tiny beating hairs, which drift through the water for up to ten days. The phenomenon has a name, stinging water, and this is the animal responsible.

Beds spread by budding as well as spawning, which is why a bay either has hundreds or none, and why they colonize new lagoons and marina basins so readily.

## Also known as

- **English:** sucker upsidedown jellyfish, suction cup jellyfish, upside down jellyfish
- **Hebrew:** מדוזה-הפוכה מטמיעה
- **French:** Méduse à l'envers indo-pacifique
- **German:** Saugschirmqualle, Mangrovenqualle
- **Spanish:** Medusa invertida de manglar
- **Portuguese:** Água-viva, Água-viva-de-ponta-cabeça-do-Indo-Pacífico
- **Czech:** kořenoústka pobřežní, kořenoústka sluneční
- **Chinese:** 倒立水母
- **Ukrainian:** Кассіопея Андромеда
- **HU:** talajlakó medúza

## Scientific synonyms

- *Cassiopea andromeda var. malayensis* Maas, 1903
- *Cassiopea picta* Vanhöffen, 1888
- *Cassiopea polypoides* Keller, 1883
- *Medusa andromeda* Forskål, 1775

## Range

Mediterranean Sea, North Atlantic Ocean, Red Sea, South Pacific Ocean

---

*Source: [Red Sea Creatures](https://redseacreatures.com/taxon/invertebrate/stinging/jellyfishes/upside-down-jellyfish)*
*Updated: August 12, 2026*