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Pacific Sea Nettle

Chrysaora fuscescens

Description

The Pacific Sea Nettle is distinguished from other jellyfish by its amber-colored bell, which is darkest near the margin. That bell can be up to three feet in diameter, but most are about a foot across. The 24 deep brown tentacles (arranged in eight groups of three) around the perimeter of the bell can be up to 16 feet long, and the 4 white, lacy-looking oral arms in the center can be up to 10 feet long.

Pacific Sea Nettle

Distribution and Habitat

Pacific Sea Nettles are found in all areas of the Pacific and Indian oceans but are most common off the shores of Japan and Siberia and from northern Alaska to Mexico.

Feeding

Unable to actively hunt for prey, the Pacific Sea Nettle must eat as it drifts. By spreading out its tentacles like a large net, the sea nettle is able to catch food as it passes by. When prey brushes up against the tentacles, thousands of nematocysts are released, launching barbed stingers which release a paralyzing toxin into the quarry. The oral arms begin digestion as they transport the prey into the sea nettle’s mouth. Pacific Sea Nettles feed on a variety of zooplankton, including other jellyfish, as well as fish eggs, baby and adult fish, crustaceans, and other floating animals.

Reproduction

Pacific Sea Nettles have a very complex life cycle made up of five stages. Their lifecycle begins when males broadcast sperm into the water and the females catch the sperm to fertilize the eggs she has produced and is holding in her mouth. The fertilized eggs remain attached to the mother’s oral arms and grow into flat jelly bean-shaped organisms called planulae. The planulae then grow into flower-shaped polyps, which are released into the ocean. Each polyp attaches to a solid surface and undergoes asexual reproduction through which it makes an exact copy of itself by budding. After the new polyp is fully formed, it is released into the ocean and starts to change shape, looking more like the adult nettle. The nettle develops a bell, arms and tentacles until it is a fully formed adult.

Other Information

Pacific Sea Nettles may form large groups just offshore on the open coast, and many may strand themselves on the beach.

Although the Pacific Sea Nettle can and will sting a human who comes into contact with its tentacles, the toxin it releases is generally harmless to most people. The sting can, however, be painful.

The Pacific Sea Nettle uses light-sensing organs called ocelli to migrate daily from dark, deep water to sunlit surface water.

Pacific Sea Nettles swim by squeezing their bell and pushing water behind them, allowing them to swim against currents, although most of the time they prefer to simply float. Sometimes they even pick up "hitchhikers," including small fish and crabs, which hide inside the sea nettle’s bell. Some of these hitchhikers feed on the sea nettle, but most are simply taking advantage of the protection afforded by the sea nettle's stinging tentacles.

Scientific Classification

phylum Cnidaria
class Scyphozoa
order Semaeostomeae
family Pelagiidae
genus & species Chrysaora fuscescens

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This page was last updated on 06/16/2017.