Lampreys digging holes to give birth to their young

During the breeding season, lampreys flock from their respective habitats to the middle and upstream sections of the river. The males choose shallow, fast-flowing, gravel-bottomed waters to build their nests. The females then arrive and build their nests together. They use their sucker-shaped mouth to suck up small stones, loosen them by dragging and shaking, and drag them to the downstream of the nest, where they build them into piles to form an oval or circular depression with a diameter of 500-800 mm. This is their ovary. After the ovaries are built, mating begins. The method of mating is very interesting. First, the female broodfish uses her mouth to attach to the stones on the nest, and the male broodfish uses his mouth to attach to the female's head. After that, the male fish attaches the rear part of his body to the head. The female fish rolls up so that the two fish form a "twist" shape. Then, the male and female fish each vibrate the rear part of their body violently, stirring up the fine sand, and at the same time discharge their eggs and sperm.

The surface of the eggs is sticky and can adhere to sand and sink to the bottom of the nest. After laying eggs, the male and female broodstock separate and immediately carry the small rocks above the nest to the pile of rocks below. Due to the strong current of the river, a lot of fine sand can be stirred up to the nest and bury the fertilized eggs. This reproduction method is repeated in a short period of time until the female fish has discharged all the eggs, and the two parent fish leave the ovary to lay eggs. Soon after breeding, all parent fish died.

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