Mangrove Upsidedown Jelly

Overview

The Mangrove Upsidedown Jelly is a unique, benthic jellyfish frequently found resting on its bell in shallow, calm waters. Unlike most jellyfish that drift through the open ocean, this species spends much of its time on the seafloor with its oral arms facing upward to capture sunlight and prey.

Distribution & habitat

Native to the Indo-Pacific region and the Red Sea, this species has expanded its range into the Mediterranean Sea via the Suez Canal and has been introduced to areas like Hawaii and Brazil. It thrives in protected, shallow environments such as mangrove-sheltered lagoons, seagrass beds, and sandy or muddy intertidal flats where water movement is minimal.

Appearance

This jellyfish typically features a flattened, disc-like bell that ranges in color from yellow to brown, often patterned with pale streaks and spots. Its appearance is influenced by symbiotic algae living within its tissues. It possesses eight oral arms that are shorter than the radius of the bell, which branch out into dense, cauliflower-like structures covered in numerous small mouthlets and stinging cells.

Biology & behavior

This species maintains a mutualistic relationship with photosynthetic dinoflagellate algae known as zooxanthellae, which live in its tissues and provide essential nutrients. The jellyfish also hosts small shrimp within its oral arms, which help remove parasites. While it prefers to remain stationary on the bottom, it is capable of swimming by pulsating its bell if disturbed. It is known to release mucus containing stinging cells into the water, which can cause skin irritation to humans.

Feeding

As a mixotroph, it relies on two primary food sources: carbohydrates produced by its symbiotic algae through photosynthesis and small prey captured by its stinging tentacles.