Chrysaora fuscescens

Chrysaora fuscescens Brandt, 1835 : Sea nettle
Phylum Cnidaria / Class Scyphozoa / Order Semaeostomeae / Family Pelagiidae
Sea nettle swarm, Chrysaora fuscescens, Pacific Grove CA, Pacific Ocean
Sea nettle swarm, Chrysaora fuscescens, Monterey CA, Pacific Ocean

Few underwater sights in Monterey Bay are more spectacular than a massive swarm of sea nettles. Nearshore aggregations are most common during fall and winter months, when dozens can be seen at one time. Sea nettles possess a distinctive golden-brown bell (up to 30 cm diameter). The whitish oral arms and thin maroon tentacles (24 in number) may trail behind for several meters. Contact with the tentacles can produce a painful sting.

Sea nettles are common visitors to California and Oregon nearshore waters, and may be found from Mexico to British Columbia. They swim continuously, usually against any current with the oral arms and tentacles extended. Prey include a wide variety of zooplankton – crustaceans, salps, pelagic snails, comb jellies, fish eggs and larvae, and other jellies. Despite the potent sting, many animals prey on sea nettles, including marine birds known as fulmars as seen in the fourth photo.

Dense swarms of thousands of sea nettles may persist in an area for many months and can be quite a nuisance for fishing activities, scientific trawls and any kind of water intake. The East Coast is also blessed with its version of the sea nettle (Atlantic sea nettle, C. quinquecirrha, bottom photo) that has a troublesome reputation. It is possible to establish polyps and culture both Chrysaora species in captivity. When provided with appropriate aquarium conditions (such as a kreisel tank), the medusae do well under captive conditions. Sea nettles have proven to be very popular for display at public aquariums.

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