Mating Plugs

In cockroaches, the physical presence of a spermatophore in the genital tract of a female may play a dual role in preventing sperm transfer from other males. Besides acting as mechanical triggers in turning off female receptivity, they may also serve as short-term physical barriers to the placement of additional spermatophores. Copulating males typically deposit spermatophores directly over the spermathecal openings. If a female accepts an additional male and a second spermatophore is inserted, it is doubtful that the second male's sperm could access female sperm storage organs. Additional spermatophores are usually improperly positioned (Roth, 1962; Graves, 1969). Spermatophore shape and its mechanism of attachment vary among cockroach taxonomic groups and some types are probably more refractory to dislodgment than others. In some blaberids the spermatophore has a dorsal groove that fits closely against the female genital papilla (Graves, 1969). In blattellids with uricose glands, uric acid deposited on the spermatophore can fill the genital atrium of the female (Roth, 1967c).

The spermatophore is discarded by the female after 20-24 hr in P. americana (Jaiswal and Naidu, 1976), after 2-3 days in Blatta orientalis (Roth and Willis, 1954b), after 4-9 days in Eub.posticus (Roth, 1968c),by the 5th day in Blab. craniifer (Nutting, 1953b), by the 6th day in D. punctata (Engelmann, 1960), and after 6-13 days in R. maderae (Roth, 1964b). Young females of N. cinerea extrude the spermatophore after 5 or 6 days, but older females may retain it for over a month (Roth, 1964b). The mechanism by which cockroach females eject the spermatophore is not altogether clear. In B. germanica, the spermatophore remains in place about 12 hr and then shrinks; the shriveled remains may adhere to the female for several days (Roth and Willis, 1952a). Jaiswal and Naidu (1976) indicate that shrinkage of the outermost layer also causes spermatophore separation in P. americana, but Hughes and Davey (1969) thought that it disintegrated as a result of exposure to spermathecal secretions. Disintegration of the spermatophore is also reported in Blab. craniifer (Hohmann et al., 1978). A secretion from the spermathecal glands apparently facilitates spermathecal extrusion in four examined Blaberi-

dae (D. punctata, R. maderae, N. cinerea, Byr. fumigata). The secretion is under the control of the corpora allata, and loosens the spermatophore by softening the material covering it (reviewed by Roth, 1970b). Nonetheless, a few experimental females of R. maderae were able to extrude their spermatophores despite surgical removal of the spermathecal glands (Engelmann, 1957).

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