How Do Earthworms Reproduce? A Detailed Explanation of Their Reproduction Methods
Earthworm reproduction: hermaphroditic, cross-fertilization, during reproduction the clitellum produces an egg cocoon to breed the next generation.
Earthworms are hermaphroditic; the male reproductive organs are on the posterior side of segments 10 and 11, with two pairs of testis sacs, each sac containing one testis and one spermatic funnel, connected through small pores in the septum to the posterior pair of seminal vesicles; the two pairs of seminal vesicles are located within segments 11 and 12. After sperm cells are produced in the testes, they first enter the seminal vesicles to develop, and once mature they return to the testis sacs and are discharged through the spermatic funnel via the vas deferens. The two vas deferens, after segment 13, run parallel in pairs, and upon reaching segment 18 they join the branches and main duct of the prostate gland, discharging through the male gonopore, which is located on both sides of the ventral surface of segment 18. The female reproductive organs include a pair of grape-like ovaries, attached behind the septum of segments 12 and 13. Mature eggs fall into the body cavity, pass through a pair of egg funnels in segment 13, travel through the shorter oviduct, converge at segment 14, and are discharged through the female gonopore; there is only one female gonopore. In addition, within segments 6 to 9, there are 2 or 3 pairs of spermathecae, which are the sites for receiving and storing sperm from another individual, opening on both sides of the ventral intersegmental grooves between segments 6 and 9.
Although earthworms are hermaphroditic, because the sex cells mature at different times, cross-fertilization is still required. The male reproductive cells of earthworms mature first. After maturation, two earthworms must mate; during mating, the accessory glands secrete mucus, causing their ventral surfaces to adhere to each other, with their head ends pointing in opposite directions. The male gonopores align with the other individual's spermathecal pores, and semen is discharged from each one's male gonopore, entering the other's spermathecae through the spermathecal pores. After exchanging semen, the two earthworms separate. Once the eggs mature, the clitellum secretes a viscous substance that solidifies outside the clitellum to form a ring-shaped mucus tube (the cocoon). Mature eggs are discharged from the female gonopore into the cocoon. As the earthworm moves backward in a wavelike motion, the cocoon gradually moves forward accordingly; when it reaches the spermathecal pores, sperm escape and fertilization occurs within the cocoon. The earthworm continues to move backward, and finally the cocoon leaves the body, with both ends sealed, remaining in the soil. Each cocoon contains 1 to 3 embryos, hatching within 2 to 3 weeks. If the environment is unsuitable, hatching may be delayed until the following spring.