Wendy Nixdorf

Degree Name

Master of Science (MS)

Semester of Degree Completion

1993

Thesis Director

Kipp C. Kruse

Abstract

The evolutionary significance of senescence and death is poorly understood. Life history theory suggests that the allocation of energy to growth or reproduction is necessarily associated with a decrease in energy available for maintenance of the soma. This study attempted to determine if an investment in reproduction would decrease longevity in the giant waterbug (Belostoma flumineum). Male and female waterbugs were collected from the field as last instar stage nymphs and maintained under controlled laboratory conditions. Individuals were randomly assigned to mating effort treatments, (virgins or breeders with breeding efforts ranging from 1 to >5 times). Following breeding, one half of the males had their egg pads artificially removed whereas the other half were allowed to brood eggs pads through hatching.

Female waterbugs lived, on average, longer than males; though when considered by level of mating effort the difference was statistically indistinguishable. Neither breeding nor number of breeding efforts had a detrimental effect on lifespan; virgins and breeders lived for approximately the same length of time. There was no significant difference between the lifespan of brooding and non-brooding males. Both male and female waterbugs that were paired with the opposite sex, yet yet failed to breed, died significantly sooner than either virgins or breeders; casual factors for this decreased longevity are uncertain. There was a significant positive relationship between age at first reproduction and age at death in both male and female waterbugs; those bugs that bred early in life died sooner than those that bred for the first time late in life. These results suggest that male and female waterbugs pay a longevity cost by reproducing early in life.

Download

Share

COinS