Mating in earthworm is a unique process, earthworm is a hermaphrodite organism. Breeding in earthworm takes place during rainy season and begins with copulation soon after maturation of the sperms.
The gametic exchange and the physiology reproduction during mating can described as below
(i) Earthworms are protandrous animal (i.e., maturation of sperm takes place much earlier then that of ova).
(ii) Mating process in earthworm occurs through cross-fertilisation.
(iii) The mating process involves exchange of sperms between the two worms.
(iv) Two individuals from adjacent burrows half emerge out and lie in contact with each other, and opposite gonadal opening exchange the packets of sperms called spermatophores.
(v) During the process, the skin encircling male pore, elevates little to form a temporary papilla that fits like a penis into the opposite spermathecal pore to keep it open.
(vi) After filling of spermathecal, the copulating worm moves a bit to adjust another pair of spermathecae to face the male pores of the other. This is accomplished in about an hour's copulation.
(vii) Within the spermathecae, the sperms mostly remain in their diverticula and the ampulla is associated with the secretion of nutritive substances for the sperms.
(viii) The sperm and egg are passed into cocoon which is secreted by clitellar gland.
(ix) Fertilisation is therefore external and cross fertilisation.
