Gyrejen

Gyrejen is a term used in speculative biology to describe a genus of gelatinous pelagic zooplankton known for forming circular aggregations called gyres. Members are translucent medusae ranging from 2 to 5 cm in diameter, with a soft, umbrella-shaped bell and short, threadlike tentacles. Bioluminescence is often observed along the bell margin, especially in low light.

Habitat and distribution: Gyrejen are described as widespread in temperate and subtropical oceans, commonly around major current systems and productive upwelling zones. They inhabit the upper water column from the surface down to tens of meters depth, and may occur in large, seasonal swarms.

Behavior and ecology: The defining feature of gyrejen is their circular swarm behavior: swarms form temporary gyres that drift with prevailing currents, and may rearrange in response to prey density or thermal fronts. Diet consists of microplankton and small zooplankton. Predators include larger jellies, fish, and seabirds. Through their feeding and mucus production, they are imagined to contribute to short-term carbon cycling and to provide prey for higher trophic levels.

Life cycle and naming: In speculative models, gyrejen alternate between pelagic medusoid stages and polyp-like stages, with reproduction largely by broadcasting eggs and sperm into the water. The name derives from gyro- meaning circle and -jen as a coined suffix. In literature and modeling, gyrejen are used as a canonical example of circular current-driven dynamics in zooplankton populations.