Anoxia-tolerant
Guides
Cloeon dipterum
Pond Olive
Cloeon dipterum is a small mayfly species with a Holarctic distribution, widespread across Europe, Asia, and North America. It is the most common mayfly in ponds of the British Isles, occurring in approximately 40% of all ponds and 70% in southern regions. The species is notable for being the only ovoviviparous mayfly in Europe: females retain eggs internally for 10–14 days after mating, and nymphs hatch immediately upon contact with water. Males possess distinctive turbinate eyes—dorsal "turban-shaped" superposition eyes that aid in locating females during mating swarms. The species has been established as a laboratory model for studying insect evolution, development, and ecotoxicology.