Formation of cocoon in earthworm, Biology

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Formation of cocoon in earthworm:
  • In earthworm segments from 14 to 17 are swollen. Skin on these segments is thick and glandular. This is called clitellum.
  • When ovaries mature, the clitellum secretes a viscous substance in the form of a girdle.
  • This girdle hardens into a cocoon around the clitellum.
  • Earthworm wriggles out of the cocoon - cocoon moves anteriorly and the worm moves posteriorly.
  • Ova are discharged into the cocoon. When the cocoon moves over the spermathecae openings. Spermatozoa received from another animal are stored in the spermathecae are discharged into it.
  • The cocoon finally comes out of the body and both ends of cocoon get closed.
  • Fertilization takes place in cocoon. Since fertilization is taking place outside the body, it is external fertilization.
  • After about 8 to 10 weeks, young earthworms come out of the cocoon.

 

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