“When 2 worms mate and they exchange sperm etc, when they withdraw, does each worm produce a cocoon or is there only one cocoon. I have been trying to find the answer to this question for some time, without success. If you can answer it for me that would be great.” ~ Kathie Oud
Thanks for your question, the answer is that they will produce 2 cocoons, one cocoon each.
After mating and the swapping of genetic material, they will each start forming cocoons for the fertilization of the eggs. Each cocoon can contain up to 20 eggs (20 potential worms), however in most composting worms, the average is 2-5 worms.
Earthworms are hermaphrodites, which means they are unisex since they posses both the female and male sex organs. Although they can each produce eggs and sperm, they can never self-fertilize and must reproduce through the swapping of sperm through mating with another worm.
The sex organ of earthworms is one of the more complex in the list of unisex animals, making it an interesting point of study.
Many people who have associated with earthworms will know the clitellum, which is a light thicker band near the head region of the worm; some may associate it as the ‘neck’ of the worm. Maybe because it is so visible to the naked eye, many people automatically think or have been told that the clitellum is the place where the sex organs are held.
Although the clitellum is an important part of the mating process, it is actually not where the sex organs are held.
The sex organs are held much nearer towards the head between the segments 9-13.
You may see that some worms don’t seem to have a clitellum, or a clitellum that is almost undetectable. All this means is that the worm is not yet sexually mature. As a worm develops and grow into sexual maturity, their clitellum band will grow larger and much more distinguishable.
Some worm farmers understand this and use this to develop a strategy for worm growing, since more mature worms in close proximity with each other will increase their chances of mating considerably.
Each worm has a pair of ovaries which produces eggs called oocyctes, which is what need to be fertilized. Different species of worms can have different number of pairs of testes (where sperm are made) and can be between 1 to 2 pairs, and these are contained in a large sack called the seminal vesicle.
The seminal vesicle contains a long tube which is where the sperm travels to reach the mate during mating.
The clitellum is important for two reasons: connecting the two worms together during mating and for the formation of cocoons.
The clitellum produces a thick mucus for the worms attachment, and the sperm is swapped between them and is then stored in each others seminal receptacle, a small compartment, until their own eggs are ready and mature. The worms then separates from each other.
Once the eggs in the ovaries are mature, each worm will form a thick mucus around their clitellum, this time for cocoon formation. This thick mucus is moved towards the head passing through the reproductive organs. Here the eggs are first picked up, and then the sperm. As the worm backs away from the mucous, it slips over its head and off the worm, hardening during the process, with the ends closing forming the lemon shaped cocoon.
Within the cocoon is where the sperms and eggs are mixed and where fertilization takes place, giving you baby worms in 4-6 weeks!