Sexual Conflict Over Sperm

Male and female reproductive interests do not always coincide, and the conflict may be evident in their genital morphology. "Disagreement" over the removal or repositioning of stored sperm can select for male genitalia better designed to penetrate the female's sperm storage organs, as well as female organs that are more resistant to male intrusion (Eberhard, 1985, 1996; Chapman et al., 2003). There is a potential example of such antagonistic co-evolution among cockroaches in the Moroccan and Spanish species of Loboptera (Blattellinae) studied by Horst Bohn (1991a, 1991b). As noted above, males have a genital whip as part of the left phallomere complex. Females have spermathecae that are multiply lobed with long, convoluted ducts and as many as 10 branches on each side (L. glandulifera). In some species, the length of spermathecal ducts appears correlated with whip length in the male (Fig. 6.19), suggesting that as the female receptacle elongates, so does the adaptive value of a long whip in potential sires (and vice versa). Some males additionally have a sclerite densely covered with bristles, or membranes covered with long, narrow, hair-like scales in the vicinity of the intromittent organ (also occurring in other genera—Fig. 6.11B). In some Loboptera species the whip itself is covered in small bristles (L. delafrontera) or is densely hairy (L. juergeni). Spermathecae appear to have valves, sphincters, or other adaptations that serve to control sperm movement or to interact with male intro-mittent organs. Ducts can have accordion-like walls (L. truncata, L. cuneilobata), or a series of irregular swellings,

Fig. 6.19 Spermathecae of female Loboptera (Blattellidae: Blat-tellinae) and corresponding genitalic structure in male. (A) Multi-branched spermathecae of L. decipiens nevadensis; (B) whip in male of the same species; (C) multi-branched spermathecae of L. barbarae (phase contrast); (D) whip in male of the same species. From Bohn (1991b), courtesy of Horst Bohn, and with permission from the Journal of Insect Systematics and Evolution ( = Entomologica Scandinavica).

Fig. 6.19 Spermathecae of female Loboptera (Blattellidae: Blat-tellinae) and corresponding genitalic structure in male. (A) Multi-branched spermathecae of L. decipiens nevadensis; (B) whip in male of the same species; (C) multi-branched spermathecae of L. barbarae (phase contrast); (D) whip in male of the same species. From Bohn (1991b), courtesy of Horst Bohn, and with permission from the Journal of Insect Systematics and Evolution ( = Entomologica Scandinavica).

giving them the appearance of a string of pearls (L. minor minor). Multiple reversals in the coiling direction of long thin, spermathecal ducts are common in the genus. Terminal ampullae may be globular, club shaped, or the same width as the spermathecal duct; branch points of ducts may be widely separated or originate from a single point. The morphological evidence for co-evolution of genital structures in male and female Loboptera is compelling; nonetheless, sexual biology and behavior in the genus are largely unknown.

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