Cannonball Jelly

Overview

The Cannonball Jellyfish (Stomolophus meleagris), often called the cabbagehead jellyfish, is a robust, spherical medusa known for its firm, dome-shaped bell. It is one of the most abundant jellyfish species along the southeastern coast of the United States and is widely distributed across tropical and subtropical waters in the Atlantic and Pacific Oceans.

Appearance

This species is easily recognized by its rigid, hemispherical bell, which can reach up to 25 cm in diameter. Its coloration varies by region; Atlantic populations typically appear milky white, yellow, or reddish, while Pacific individuals often exhibit bluish or gray hues. A distinct brown pigment frequently borders the margin of the bell. Instead of long, trailing tentacles, it possesses a cluster of 16 short, complexly branched oral arms beneath the bell that aid in both propulsion and prey capture.

Biology & Behavior

Cannonball jellyfish are strong, active swimmers that utilize their oral arms to move through the water column. When threatened or disturbed, they can secrete a mucus containing toxins that may deter most predators and harm small fish. While they are not considered dangerous to humans, their toxins can cause cardiac issues in some animals. They play a vital ecological role as a primary food source for the endangered leatherback sea turtle. Interestingly, these jellyfish are sometimes harvested commercially for export to Asian food markets.