Spotted jelly. Mastigias papua.
This species is also known as a “lagoon jelly” because it lives in bays, harbors and lagoons in the South Pacific. Spotted jellies have rounded bells and strange clumps of oral arms with clublike appendages that hang down below. Instead of a single mouth, they have many small mouth openings on their oral-arms, which capture small animal plankton. In addition, each jelly grows a crop of algae, which gives them a greenish-brown color. They harvest some of their food directly from the algae.

Species Information

Diet
zooplankton, food produced by tiny algae (called zooxanthellae).

Size
up to 2 feet (61 cm) in diameter

Range
South Pacific Ocean, Hawaii and Puerto Rico

Relatives
blue jelly; Family: Magistiidae

Conservation Notes
The number of spotted jellies in some lakes on Palau island (part of Micronesia in the Western Pacific) declined dramatically in 1998. After studying the lakes, scientists think the jellies disappeared because of changes in the lake water due to the very severe El Ni??o of 1997-98. The temperature of the lakes rose, as did the saltiness, creating an unhealthy environment for the jellies. By the year 2000, jelly numbers were on the rise.

Cool facts
Some of the larger spotted jellies actually have small fishes living with them. The fishes use the inside of a jelly’s bell as protection from larger predators until they reach maturity.

Spotted jellies swim in huge swarms to stay in the direct rays of the sun???the sun’s rays fuel the growth of the symbiotic algae the jellies thrive on. At night, spotted jellies descend to deeper waters, to an anoxic (oxygen-deficient) layer that's high in concentrations of hydrogen sulfide. There, the jellies absorb ammonium, which acts just like fertilizer on the algae.

Text from Monterey Bay Aquarium (http://www.mbayaq.org/)