Japanese sea bettle

The umbrella of Chrysaora pacifica is almost hemispherical, divided into eight sectors, with a flexible and translucent mesoglea, thicker in the center.

Its maximum size reaches about 20 cm in diameter, with collected specimens generally ranging between 15 and 21 cm, which distinguishes it from C. melanaster which can exceed 30 cm.

The exumbrella (upper surface) is finely granulated and adorned with 32 brown radial stripes radiating from the center, sometimes of the "sunburst" type. The subumbrella (lower surface) does not show the characteristic black streaks of C. melanaster.

The species has four delicate oral arms, wrinkled in appearance like a curtain (hence its Korean name Keoteun-wonyang-haepari), measuring two to three times the length of the umbrella's diameter. These arms are covered with numerous stinging warts (nematocysts).

The capture system includes 40 filamentous tentacles, orange-brown in color, exceptionally elastic and capable of reaching two to three times the diameter of the umbrella in living specimens.

Coastal pelagic species, Chrysaora pacifica makes regular seasonal appearances, mainly from spring to summer (May to September) in Korean and Japanese waters. It is capable of actively swimming but remains largely dependent on currents for horizontal movements. Wild polyps have been identified in Sagami Bay, Japan, confirming the presence of a benthic phase in its cycle.

The species is known to form dense aggregations near the coasts during its peak abundance period, increasing the risks of encounters with human activities (swimming, fishing). A carnivorous predator, this species actively captures zooplankton and small pelagic organisms with its vast network of 40 stinging tentacles. Its specialized oral arms then allow for the manipulation and ingestion of prey. Its morphology and belonging to the genus Chrysaora indicate effective predation on fish larvae, planktonic crustaceans, and potentially other smaller jellyfish.

Like all Scyphozoans, C. pacifica exhibits an alternation of generations. The sexual phase (jellyfish) releases gametes that give rise to a planula larva. This larva attaches to form a polyp (scyphistome), a stage that has been observed in the wild in Sagami Bay.

The polyp reproduces asexually through strobilation to release young jellyfish (ephyrae). The species is gonochoric (separate sexes). The confirmed presence of wild polyps suggests a well-established life cycle in its North Pacific distribution range.