Alona intermedia is one of the smallest Alona-species with a postabdomen that widens strongly towards the end. It is quite common and characterised as moderate acid sensitive.

Key characteristics

A. intermedia is one of the smallest Alona-species, having a thin and transparent carapace. The head shield has only two head pores. Its postabdomen widens strongly towards the end and is evenly rounded. The spines at the basis of the abdominal claws are especially long and characteristic, and A. intermedia may be easily distinguished from the other Alona-species. The carapace has a distinct striation and is punctuated. Its colour is yellowish grey or greenish grey often with a tinge of brown.

Female: Length 0.3–0.5 mm

Male: Length 0.2–0.3 mm

Ecology and distribution

A. intermedia is recorded in 8 % of the investigated lakes, and is distributed all over the country. It occurs from sea level and up to the alpine zone (1376 m a.s.l.) with highest frequency below 500 m a.s.l. The species is evenly found in localities of all sizes, but is rare in acid water and is classified as acid sensitive. It is only found twice at pH<5.0. Though A. intermedia is found in electrolyte-poor water (0.6 mS/m), it most commonly occurs in electrolyte-rich waters.