Atolla

Atolla is a genus of deep-sea jellyfish in the class Scyphozoa, best known for the species Atolla wyvillei. Members of this genus are medusae with a relatively small to medium, bell-shaped body and a crown-like arrangement of marginal structures, giving them a distinctive appearance in the dim deep sea. Adults typically range from a few centimeters in diameter, depending on the species.

Distribution and habitat: Atolla species inhabit the bathypelagic zones of the world’s oceans, often at depths of several hundred to a few thousand meters. They are not commonly encountered in surface waters and are usually collected from deep-water trawls or observed with submersibles.

Biology and behavior: These jellyfish are predatory, feeding on zooplankton and small crustaceans. They are noted for bioluminescence, producing a red glow in response to stimulation. This light emission has been discussed in ecological terms such as the burglar alarm hypothesis, which proposes that luminescence could attract higher predators to deter attackers, though the exact function of the glow remains a topic of study.

Life cycle: Like other scyphozoans, Atolla species undergo a life cycle that includes a free-swimming medusa stage and a polyp stage, with sexual reproduction generating planula larvae that develop into new medusae. The deep-sea habitat often means the polyp stage is rarely observed directly.

Taxonomy and discovery: The genus Atolla was established in the history of jellyfish research, with Atolla wyvillei as the most prominent representative. Ongoing deep-sea research continues to refine understanding of the diversity, distribution, and ecology of this group.