Degree Name

Master of Science (MS)

Semester of Degree Completion

1996

Thesis Director

Kipp C. Kruse

Abstract

Senescence is the process by which organisms age and ultimately die. Life history theory suggests that the allocation of energy into growth and reproduction is necessarily associated with a decrease in energy available for the maintenance of the soma. Many studies have shown that early or increased rates of reproduction are often correlated with a decrease in longevity, but few studies have investigated physiological correlates to this event. Catalase is an enzyme involved in the removal of oxygen free radicals implicated in damaging cellular components that contribute to senescence. A decrease in catalase activity with age could increase the organism's maintenance cost and lead to an increased rate of senescence. This study investigated the possibility that changes in catalase activity are related to the energy trade-off between reproduction and longevity in the giant waterbug, Belostoma flumineum. This species is a good model for this type of investigation because both males and females contribute a significant amount of parental investment.

Waterbugs were collected as fifth instar nymphs and maintained under controlled laboratory conditions. Males and females were randomly allocated to either virgin or breeder reproductive treatments. Waterbugs were assayed for catalase activity at ages of 10, 60, 100, and 150 days.

Catalase activity/ g bug was shown to increase with chronological age in male and female virgins, but not in breeders of either sex; most of this change was early in life (0-60 days). Virgin bugs also had higher catalase activity I g bug than those that were allowed to breed. This might suggest that waterbugs that breed are less protected from free radical damage than virgins, and could help explain the shortened life span of breeders relative to virgins.

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