Culture of fish food organisms (1+1)

Unit 6 - Microworms

6.2.3.Copulation and cocoon formation
Although the Tubifex worm is a hermoprodite, the male and female organs become mature at different times; and thus self-fertilization is avoided, and cross fertilization is encouraged. Two mature Tubifex worms undergo copulation by joining their ventral and anterior surfaces together with their anterior ends pointing opposite directions. Thus the spermathecal openings of each Tubifex worm be nearer to the male apertures of another worm. The penial setae of one Tubifex worm penetrate into the tissues of other worm and thus the conjugants are held together. At this stage the sperms of one worm are passed into the spermathecae of the other worm. After copulation the Tubifex worm separate and begin to produce egg cases containing eggs. These egg cases are called cocoons. The cocoon is formed around the clitellum as a soft box-like structure into which the ova and the sperms are deposited. Soon the Tubifex worm withdraws its body from the egg case by its backward wriggling movements. As the worm withdraws, the cocoon completely closes and become a round shaped case. The case contains both sperms and ova. After fertilization several eggs are formed in the cocoon. The fertilized eggs undergo complete development in the cocoon by utilizing the albuminous nutritive fluid for growth. The period of development varies with temperature and lasts for two to three weeks. After complete development the young worms come out of the cocoon.