Common Moon Jelly

Overview

The Common Moon Jelly is a widely recognized, translucent jellyfish characterized by its saucer-shaped bell and four distinct, horseshoe-shaped gonads visible through its upper surface. Primarily a coastal species, it is frequently encountered in temperate and tropical waters, where it drifts with currents and tides. While it possesses stinging cells, its effect on humans is typically mild or negligible.

Appearance

This species features a nearly transparent, gelatinous bell that can reach up to 40 cm in diameter. The four central gonads are a key identifying feature, appearing white or yellow in females and pink or violet in males. The margin of the bell is lined with numerous short, fine tentacles, and four oral arms hang from the underside to assist in capturing prey.

Distribution & habitat

Common Moon Jellies are highly adaptable and inhabit a variety of environments, including coastal bays, estuaries, fjords, and open ocean waters. They are tolerant of a wide range of temperatures and salinity levels, allowing them to thrive in diverse marine settings across the globe.

Feeding

As a carnivorous predator, the moon jelly feeds primarily on zooplankton, including copepods, mollusks, crustaceans, and fish larvae. It captures food by trapping organisms in mucus on its bell surface, which are then transported to the mouth by ciliary action. Recent observations also indicate they may opportunistically consume swarming polychaete worms.

Reproduction

Their complex life cycle alternates between a stationary benthic polyp stage and a free-swimming pelagic medusa stage. During the medusa phase, they reproduce sexually, with males releasing sperm that females collect to fertilize eggs. These develop into larvae that eventually settle on the seafloor to become polyps, which later undergo asexual budding to release new juvenile jellyfish.