Prof. Gowaty, TA: Meachen-Samuels
Protocol Rough Draft
“Does Sexual Cannibalism Result in Increased Offspring Viability in
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).
Roeder (1935) show that female mantises are known to decapitate and devour
their mates’ heads either prior to or after the act of copulation.
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.
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.
Study Species, Study Site:
The species of mantis to be studied for this experiment will be
, a relatively large mantis with apparent sexual dimorphism:
females are up to five times heavier than the males (Birkhead, 1988).