Amur Bitterling, Rhodeus sericeus
The Amur Bitterling, (Rhodeus sericeus), is a species of fish in the carp family. This species is sometimes just called “bitterling.” However, bitterling properly refers to any species in the entire genus Rhodeus. This species is found in Siberia.
Mussels are an essential part of the Bitterling’s reproductive system, with bitterling eggs being laid inside them. It was long believed that bitterling and mussels were symbiotic — as mussel larval attaches to fish gills during development. However, recent research has indicated that the bitterling is parasitic, with co-evolution being seen in Chinese bitterling and mussel species.
Bitterlings usually reside in areas with dense plant growth. They are hardy and can survive in water that is under-oxygenated. They grow to between 3 and 4 inches in length. Their diet consists of plant material and small larval insects.
Image Credit: George Chemilevsky/Wikipedia