Lamprey

Lampreys belong together with Hagfishes to the most primitive group of vertebrates called Cyclostomata. They do not have any ossified bones in their bodies, skeletal system is made of cartilagine. As their name suggests they do not have any jaws. However, mouthparts are complicated with strong tongue and horny teeth. Lampreys have very unusual biology that starts in fresh water when a female lays eggs and both parents die right after that. Larvae that hatch from eggs live burried in riverbeds where they feed by filtrating substrate. After several years they undergo the process of metamorphosis after which some species migrate to oceans where they totally change their feeding strategy and become predators. They firstly attack small animals, then fishes to whom they inflict deep wounds and suck their flesh and blood. Attacked fishes usually die. Some species of lapmreys stay, hovewer, in fresh water their entire life.They usually don´t feed at all when reaching adulthood (lasting for 6 months) and have reduced and partly closed digestion system. Only small part of lampreys that stay in fresh water when adults become predators.