food produced by tiny plants called zooxanthellae; zooplankton
up to 1 foot (30 cm) wide and 2 inches (51 mm) high
sea nettle, moon jelly; Family: Cassiopeidae
tropical waters in the Indo-Pacific Ocean, the Caribbean, Southern Florida and Hawaii
Down is up for this jelly—it rests its bell on the seafloor and waves its lacy underparts up toward the sun. Why? This jelly is a farmer. Its brownish color is caused by symbiotic algae living inside the jelly's tissues. By lying upside-down, the jelly exposes its algae to the sun, allowing it to photosynthesize. The jelly lives off food the algae produce, as well as zooplankton.
An upside-down jelly doesn't have a central mouth—instead, the edges of its eight oral arms are fused and folded into elaborate frills containing hundreds of tiny mouth openings. The mouth openings are connected by channels to its stomach. By pulsing its bell, it forces zooplankton into the nematocysts on its mouth openings.
Upside-down jellies are more vulnerable than jelly species that live in the open ocean or the deep sea. They live in mangrove forests and shallow lagoons along tropical coasts. Mangrove forests are among the most threatened ecosystems on Earth; they're constantly under siege from coastal development or questionable farming practices. People clear mangroves to build hotels, housing and fish farms. Pollution flows into mangrove forests from these coastal developments, endangering all life in this rich forest habitat.
This jelly is rarely found alone—it flips upside-down alongside others of its kind. Turned upside-down, with stubby oral arms pointed toward the sun, the jelly looks like a flower. It can grow to the size of a pie plate.
This jelly is a favorite meal for ocean sunfish and the endangered leatherback sea turtle.
The upside-down jelly uses its bell much like a suction cup to stick to the seafloor.