Sea Nettle

• The fertilised female holds her eggs on the oral arms, where they develop into flower-shaped polyps.
• It eats zooplankton, crustaceans, salps, pelagic snails, small fish and other jellyfish.
• Its tentacles can reach 4.5 metres long.
• comportamientoIt can form mass swarms of thousands known as blooms, whose appearance is sometimes linked to changes in water temperature or pollution.
• Its amber bell and its extremely long oral arms, up to four metres, make it one of the most photographed jellyfish in the world, and it is the star of North America's aquariums.
• Its captive breeding was worked out at the Monterey Bay Aquarium, which developed the circular-flow tanks called kreisels, designed specifically to keep jellyfish without their becoming trapped against the walls or the filters. That technology is the reason there are jellyfish in the world's aquariums today.
• It is an efficient predator of zooplankton and of fish eggs and larvae, and its blooms in the California Current compete directly with the pelagic fish.
• Its sting is painful but not dangerous.
• Its populations fluctuate widely from year to year with the upwelling cycles, and that variability has made it an indicator of oceanographic conditions in the north-east Pacific.

Skeleton type

Invertebrate - no skeleton (gelatinous cnidarian)

Habitat & environment

Temperate waters of the north-eastern Pacific, from Mexico to British Columbia, especially off California and Oregon

Birth weight

Microscopic planula larva after fertilisation

Size at birth

An ephyra a few millimetres across as it breaks away from the polyp

Litter / clutch size

Numerous fertilised eggs held in the female's oral arms until the polyp stage

Lifespan in captivity

1-2 years in captivity (estimated from related species in the genus Chrysaora)

Sources consulted: Life in Water (Fandom); Pacific Science (life cycle study); Ocean Info; Mexican Marine Life; Animalia.bio; The Biofiles (Wikipedia); Reeflex