Protocol comments

Protocol comments - Miles Meyer EEB 187-2 Prof Gowaty TA...

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Miles Meyer 3/1/08 EEB 187-2 Prof. Gowaty, TA: Meachen-Samuels Protocol Rough Draft I. “Does Sexual Cannibalism Result in Increased Offspring Viability in Praying Mantises?” II. Introduction Sexual Cannibalism, when a male is eaten by the female before, during, or after copulation or mating is a well documented phenomena in invertebrate species such as mantises (Birkhead, 1988; Fagan, 1991; Hurd, 1994; Lelito, 2006; Liske, 1984; Loxton, 1979; Maxwell, 1999; Prokop, 2005 & Roeder, 1935) , certain scorpions and numerous arachnids (Arqvist, 1992; Buskirk, 1984; Johns, 1997; Prenter, 2006 & Thornhill, 1976, 1983). Studies by Roeder (1935) show that female mantises are known to decapitate and devour their mates’ heads either prior to or after the act of copulation. Males were even observed to engage in copulation behavior more aggressively after their heads were removed (Roeder, 1935). Despite numerous studies, sexual cannibalism is still misunderstood. More importantly, none of the previous studies (Fagan, 1991; Hurd, 1994; Lelito, 2006; Liske, 1984; Loxton, 1979; Maxwell, 1999; Prokop, 2005 & Roeder, 1935) have made it clear whether or not the male is nutritionally valuable enough to provide adaptive significance for the female (Fromhage, 2003), or for the offspring viability. Lab observations by Birkhead (1988) of mantis sexual behavior under food restriction suggests that sexual cannibalism may be adaptive for females and maladaptive for males (p.117). Conversely, Buskirk (1984) and Roeder (1935) suggest that cannibalism may be adaptive for males if opportunities for mating with females were limited and if the males could increase his and his mate’s fecundity by being cannibalized. I believe that sexual cannibalism can be adaptive to the male by increasing his offspring’s viability through providing the female with vital nutrients during oogenesis, thereby increasing the likelihood of his genes being passed on. My methodology for testing this hypothesis follows Birkhead’s (1988) study, using the ratio of offspring to survive to adulthood to offspring hatched as a measure of viability. Birkhead’s (1988) study used the dry weight of the female’s ootheca or egg pouch as an indicator of fecundity without quantifying the number of hatchlings that survive to adulthood as an indicator of viability. In this paper, I propose a study of measuring the variability in mantis offspring viability as a result of the occurrence or absence of sexual cannibalism. III. Methods Study Species, Study Site: The species of mantis to be studied for this experiment will be Hierodula membranacea , a relatively large mantis with apparent sexual dimorphism: females are up to five times heavier than the males (Birkhead, 1988). The
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species Hierodula membranacea is an ideal candidate for this experiment due to their size dimorphism between sexes, females deposit ootheca that are easily weighed, quantifiable offspring and are documented to exhibit sexually cannibalistic behavior (see Birkhead, 1988). For the site of observations and experiments I plan on using Moffett Field’s Hangar One located about three miles north of Mountain View, Ca in the Santa Clara County.
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