Brook Lamprey - Lampetra planeri
Although classed as fish, lampreys are possibly less closely related to true/boney fish than human beings are. Lampreys have cartilage skeletons and no jaws. Instead they have a sucker mouth ringed with small teeth. They are also extremely slimy to the touch, more like molluscs than fish.
This species is the smallest known, measuring only about 20cm long and resembling small ribbon-like eels. Wicklow is a great place to see them, when they mate over a period of days in shallow streams with rock and pebble beds. Their mating activity is extraordinary, as they writhe and thrash about, occasionally snatching pebbles and dragging them along the bottom in their ecstacies.
The males and females twine around each other, twisting and gripping with their sucker mouths. The females relsease eggs into the water and the males release clouds of sperm at the same time. The fertilised eggs become embedded in sand or gravel and slwoly develop over a period of six years. When they eventually hatch out the larvae embed themselves in the same substrate and snatch tiny planktonic creatures that the current carries their way.
After five years they reach adulthood, and cease to feed. The adults make their way to spawning beds and die from exhaustion after mating over a period of days.