A living fossil
At first glance, the brook lamprey is reminiscent of a small eel. But even if it looks like one, it is not a fish. It belongs to the very original group of cyclostomes. Lampreys do not have a jaw and have eight orifices arranged in a row on both flanks behind each eye. In the past, these structures were mistakenly interpreted as additional eyes, which is what gave the brook lamprey its name. In fact, seven of these openings house gills and one the olfactory organ.
The brook lamprey spends a large part of its life in a larval stage, which is known as the Querder. The Querder sit in the bottom of the water and feed on dead plant material and algae. After about 4 to 5 years, the Querder transform into adult brook lampreys, mate, lay their eggs and die.