Petromyzontidae, also known as octopus and Qixingzi, is a family of lampreys in lampreys subclass, and its suborder is one of the few existing jawless vertebrates. The oldest lamprey fossil has a history of 360 million years, before dinosaurs appeared. Therefore, lamprey is called "living fossil" and plays an important role in studying the evolution of vertebrates.
Lamprey's side is oblate, and its tail shape is original tail shape, with a body length of about 30cm. The body is divided into three parts: trunk and tail. The skin is bare and scaly.
Head: a single nostril is opened on the straight line between the two eyes on the top of the head, and the pineal gland eye is in the skin behind the nostril; The top eye is located below the pineal eye; There are 1 pairs of eyes without eyelids before the opening of branchial bursa on both sides of the head; Located on both sides of the head and behind the eyes, there are 7 round gill slits (hence the name lamprey). Some people used to think that its gill slits are eyes, seven gill slits and eyes have eight holes, so it is also called eight-eyed eel.
On the ventral side of the front end of the body, there is a circular funnel-shaped mouth funnel without a lower jaw. There are yellow horny teeth on the inside of the mouth funnel and special "file teeth" with horny teeth on the tongue end.
Trunk: Only odd fins, no lateral fins. There are 1-2 dorsal fins in the dorsal midline. The dorsal fin of male and female adults is different, and the second dorsal fin of male is higher.
Tail: A kind of caudal fin, whose shape is symmetrical with the internal skeleton, showing the original tail shape.
Relationship with human beings
An East Asian lamprey that once lived in the ocean became an invasive species after being accidentally brought into the Great Lakes of North America.
Because adult lampreys in East Asia feed on the blood of other fish, their invasion has caused great losses to the fisheries of the Great Lakes, especially the sand eel and the migratory whitebait salmon.
The European lamprey is also a kind of food, and the upper class in Europe has regarded it as a delicacy since the Middle Ages. According to the literature, King Henry I of England loved to eat European lampreys, and once died after eating too many European lampreys in Normandy.
Until today, in some countries in southern Europe (France, Spain, Portugal, etc. ), lamprey is still an expensive famous dish. Due to overfishing, the population of lamprey in Europe has been decreasing.