Description: It is a medium-to-large jellyfish belonging to the class Scyphozoa, characterized by a semi-spherical, translucent bell that usually reaches 20–35 cm in diameter, displaying milky or whitish tones crossed by subtle radial patterns. The margin bears numerous long, slender tentacles capable of delivering moderate stings, while four elongated and finely branched oral arms assist in prey capture and transport. Its delicate appearance contrasts with the effectiveness of its feeding and defensive structures.

Geographic distribution: This species is widely distributed in the southwestern Atlantic Ocean, ranging from southern Brazil to northern Patagonia in Argentina, including the Río de la Plata estuary and the Uruguayan coastline. Occurrence is often seasonal, with higher abundance during warmer months when environmental conditions favor reproduction and recruitment. It represents a characteristic component of temperate South American coastal jellyfish communities.

Habitat: It primarily inhabits shallow coastal waters, bays, and estuarine environments, where biological productivity is high. The species tolerates substantial fluctuations in salinity and temperature, allowing it to thrive in areas influenced by river discharge. Individuals are commonly observed near the surface or within the upper water column, especially during calm conditions. Its presence is strongly associated with high plankton availability, making it an important element of coastal pelagic ecosystems.

Feeding: The diet consists mainly of zooplankton, including copepods, crustacean larvae, small fish, and pelagic eggs. Prey capture occurs through cnidocytes located on the tentacles, which release immobilizing toxins upon contact. The oral arms then transport captured organisms toward the central mouth. This feeding strategy enables the exploitation of abundant microscopic prey and positions the species as an efficient predator in surface food webs.

Behavior: The species displays a largely passive drifting behavior, combining rhythmic bell contractions with the influence of ocean currents. It may form dense aggregations or blooms, particularly when environmental conditions enhance larval survival and prey availability. Such blooms can alter plankton dynamics and create competitive interactions with planktivorous fish.

Reproduction: Like other scyphozoans, it exhibits a complex life cycle with alternating sexual and asexual phases. Sexual reproduction occurs in the medusa stage through gamete release into the water column. After fertilization, the planula larva settles on a substrate and develops into a polyp, which later produces juvenile medusae through strobilation.

Conservation status: The species has not been formally assessed at a global scale and is not currently considered threatened. In some areas, increased occurrence has been linked to human-driven environmental changes, including eutrophication and reduced pressure from natural predators.

Author of this compilation: EcoRegistros – 01/18/2026