Limnomedusae

Limnomedusae is an order of cnidarians belonging to the class Hydrozoa. These are small, typically freshwater jellyfish. Unlike most jellyfish, which are marine, limnomedusae are adapted to life in freshwater environments. Their bodies are generally bell-shaped and possess tentacles that hang downwards. They exhibit a typical cnidarian life cycle, which includes a polyp stage and a medusa (jellyfish) stage, though the relative importance and visibility of these stages can vary among species.

The polyp stage is usually sessile and attached to a substrate, while the medusa stage is free-swimming. Limnomedusae are carnivorous, feeding on small invertebrates like zooplankton and insect larvae. They capture prey using stinging cells called nematocysts, which are located on their tentacles. Reproduction can be sexual, with the medusae releasing gametes, or asexual, through budding from the polyp.

Several families are included within the order Limnomedusae, such as the Olindiidae and Microhydrulidae. Some species, like Craspedacusta sowerbii, are widely distributed and can form large populations in lakes and reservoirs. The presence of limnomedusae in an aquatic ecosystem can sometimes be an indicator of water quality, as some species are sensitive to pollution. Their ecological role includes acting as both predator and prey within freshwater food webs.