Secondary Effects of Copulation

The primary role of copulation is egg fertilization, but a variety of secondary effects also occur. In cockroaches these include the suppression of female receptivity, but also diverse processes that facilitate female reproduction, such as the acceleration of oocyte growth, the prevention of oocyte degeneration, an increase in the number of oocytes matured and oviposited, the appropriate construction of the egg case, and, in ovoviviparous species, its proper retraction. The degree to which mating influences these processes as well as the details of their physiological control vary among studied species (Griffiths and Tauber, 1942a; Wharton and Wharton, 1957; Roth and Stay, 1961, 1962a, 1962c; Engelmann, 1970; Roth, 1970b; Adiyodi and Adiyodi, 1974; Hales and Breed, 1983; Goudey-Per-riere et al., 1989). These secondary effects clearly promote female reproductive fitness, but are also considered beneficial to the male because they increase the likelihood that his sperm will be used by the female to sire her eggs (reviewed by Cordero, 1995; Gillott, 2003).

Mating has been shown to stimulate oocyte maturation in all cockroach species studied to date (Holbrook et al., 2000b), but the instigating stimuli differ. The physical presence of the spermatophore, stimulation from male genitalia, mechanical pressure from a filled spermatheca, and the chemical presence of the spermatophore all have varying degrees of influence on female reproductive processes. The action of these stimuli also may be moderated, sometimes strongly, by nutritional and social factors. The mechanical stimulation caused by the firm insertion of the spermatophore in N. cinerea not only suppresses female receptivity, but is also responsible for stimulating oocyte development and for ensuring the normal formation and retraction of the ootheca during the first reproductive cycle (Roth, 1964b). The physical presence of the spermatophore has been similarly demonstrated to be sufficient stimulus for accelerating oocyte maturation in oviparous Su. longipalpa; an artificial spermatophore is a reasonable substitute (Schal et al., 1997). Diploptera punctata females are dependent on spermatophore insertion for rapid development of their oocytes. However, the act of mating alone, without passage of a spermatophore, may be sufficient for oocyte maturation in some females. The physical stimulus of the spermatophore together with the action of the male genitalia appear to produce maximum reproductive effects (Roth and Stay, 1961). The acceleration of oocyte growth that occurs after mating in P. americana can be prevented by removing the spermatophore prior to the movement of sperm into the spermatheca, or by mating the female to males whose spermatophores are of normal size and shape but lack sperm. Pipa (1985) concluded that the stimulus for oocyte growth in this species originates from the deposition of sperm or other seminal products into the spermatheca. The proper formation and retraction of the ootheca into the brood sac in N. cinerea (Roth, 1964b) and Pyc. indicus is dependent on the presence of sperm in the spermatheca. After spermatheca removal, severance of spermathecal nerves, or mating with castrated males, females produced abnormal egg cases or scattered the eggs about (Stay and Gelperin, 1966).

Male accessory glands typically contain a variety of bioactive molecules that, when transferred to the female during mating, influence her reproductive processes (Gillott, 2003). The spermatophore of Blab. craniifer is richly invested with enzymes whose activities change during the three days subsequent to mating; the longer the spermatophore remains in place (from 0-24 hr), the sooner oviposition occurs. Acetone extracts of the sper-matophore topically applied to the female induce the same increases in vitellogenesis as do juvenile hormone mimics. Nonetheless, the physical presence of the spermatophore is also required for the full expression of reproductive benefits, and both mechanoreceptors and chemoreceptors are found in the bursa (Brousse-Gaury and Goudey-Perriere, 1983; Perriere and Goudey-Per-riere, 1988; Goudey-Perriere et al., 1989).

In many cockroach species the female either internally digests and incorporates, or removes and ingests the spermatophore sometime after it is transferred to her (Engelmann, 1970). However, there is currently little evidence that spermatophores are of nutritional value, aside from the uric acid that covers them in some species. Mullins et al. (1992) injected 3H leucine into male B. germanica. The males transferred it to females during mating, who sub sequently incorporated it into their oothecae. The source of the leucine-derived materials is unknown, but the authors suggested that it may have originated from the sper-matophore or seminal fluids.

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