Oviposition behaviour in the clitellate annelid Tubifex tubifex: video recordings of mature worms under laboratory culture conditions

In the present study, videos were recorded to observe oviposition in living, mature worms of Tubifex tubifex. After the formation of a lemon shaped cocoon around the clitellum at segments 11 and 12, mature eggs that have been stored in the ovisac at segments 12–14 begin to move into segments 11–12 through the constricted posterior end of the cocoon. Within a second or so, ovisac eggs emerge out of the posterior margin and return to the posterior segments. Such movements are repeated several times before the ovisac eggs settle in the ovarian coelom of segment 11. Within a few seconds of the eggs moving into the ovarian coelom, the clitellar region begins to change its contour slightly; it looks as if something round is tapping on the coelomic wall of this region. As this tapping ceases, the coelomic eggs begin to move to the space between the cocoon and the clitellum. Coelomic eggs are individually squeezed out of the female gonopores located near the midpoint of the cocoon. This process, referred to as egg deposition, is accomplished within 30 s. The egg deposition is followed by the backward withdrawal of the anterior segments from the cocoon.