Degree Name

Master of Science (MS)

Semester of Degree Completion

1987

Thesis Director

Kipp C. Kruse

Abstract

Female water bugs (Belostoma flumineum) deposit eggs in a mucilaginous cement on the back of conspecific males, who then brood these eggs until hatching. Sex role reversal, in which females compete for males and males are discriminating, is predicted in this species because males provide parental care exclusively, and represent a limited resource. Presumably the advantage of this paternal behavior is increased survival of young. However, the potential exists for this egg-brooding behavior to incur evolutionary costs, and quantifying some of these costs was the thrust of this study.

One cost, a loss of polygynous opportunity, was investigated in both laboratory and semi-natural field conditions by measuring the length of time the male spends brooding to the time females spend between successive clutches. Results suggest that females, after ovipositing one clutch of eggs, will oviposit a second clutch before her first clutch has hatched, if a mate is available. This suggests a cost of decreased polygynous opportunity for the male.

Presumably, male water bugs would be less able to escape predators or capture prey while egg-ladden because of decreased swimming capabilities. Therefore an experiment was designed to measure swimming speed. Encumbered male B. flumineum swam significantly slower than unencumbered males or females. In addition, an experiment was undertaken to measure food intake. It was found that males eat less during the brooding period than after hatching. Therefore swimming speed reduction and decreased feeding may also be potential costs to male care.

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