Ecology and Invasion Dynamics of Freshwater Jellyfish

Freshwater jellyfish, chiefly represented by the hydrozoan Craspedacusta sowerbii, exhibit a complex metagenetic life cycle comprising benthic polyps and pelagic medusae. Native to East Asian river systems, C. sowerbii has become globally invasive, colonising temperate lakes and reservoirs on all continents except Antarctica. Polyps attach to submerged substrates and reproduce asexually, forming colonies that release medusae under favourable thermal and hydrological conditions. Medusae act as voracious predators of zooplankton, often overlapping trophic niches with native invertebrates and small fish, with the potential to trigger local food-web shifts and nutrient redistribution. Dispersal of resting stages via waterfowl, aquarium equipment and ballast water facilitates episodic medusa outbreaks in novel habitats. Invasion success is further enhanced by broad thermal tolerance, allowing medusae to persist under warming regimes and expand into higher latitudes. Despite increasing records of medusa sightings, the ecology, distribution and seasonal dynamics of polyps remain poorly understood, hampering early detection and management. Integrating population biology, ecological modelling and targeted sampling of benthic stages is essential to anticipate future range shifts, assess ecosystem impacts and inform mitigation strategies for this under-studied group of freshwater cnidarians.

Research from Nature Portfolio

Species distribution modelling reveals that precipitation, vapour pressure and temperature strongly govern the habitat suitability of C. sowerbii. Projections to mid and late twenty-first century scenarios indicate notable range expansion into high-latitude regions of both hemispheres, with reductions only in certain oceanic zones. These forecasts suggest that climate change will lengthen the seasonal window for medusa emergence and intensify invasion pressure on already vulnerable freshwater systems, calling for proactive monitoring in predicted hot spots.

Ecology and Invasion Dynamics of Freshwater Jellyfish publication trend

The graph below shows the total number of articles in ecology and invasion dynamics of freshwater jellyfish across all publications each year (not limited to Nature Index journals).

Technical terms

Medusa: The free-swimming, sexual life stage of a cnidarian that pulsates to capture prey and disperse gametes.

Polyp: The sessile, asexual life stage of a cnidarian that attaches to substrates and produces medusae through budding.

Metagenetic life cycle: A biphasic cycle alternating between solitary or colonial polyps and free-living medusae.

Species distribution model: A computational approach that correlates known species occurrences with environmental variables to predict potential geographic ranges.

Trophic niche: The ecological role of an organism defined by its feeding relationships, prey selection and position in the food web.

References

1. Trophic Positions of Polyp and Medusa Stages of the Freshwater Jellyfish Craspedacusta sowerbii Based on Stable Isotope Analysis. Biology (2023).
2. Predicting the current and future global distribution of the invasive freshwater hydrozoan Craspedacusta sowerbii. Scientific Reports (2021).
3. Hidden gems: Scattered knowledge hampered freshwater jellyfish research over the past one‐and‐a‐half centuries. Ecology and Evolution (2024).
4. Life Cycle Transitions in the Freshwater Jellyfish Craspedacusta sowerbii. Biology (2024).