Murray State Theses and Dissertations

Abstract

The differences in energetic input between the sexes required to produce gametes translates to the differences in reproductive behavior and overall mating systems seen in a species. Females generally produce a few energetically and resource expensive eggs and typically choose a high-quality suitor to ensure she has high quality offspring. In contrast, males produce abundant energetically cheap sperm and attempt to fertilize as many eggs as possible in as many females as possible. Both sexes are trying to maximize their inclusive fitness, but the dichotomy of interests can lead to sexual conflict and perhaps extreme or unusual behaviors such as sexual cannibalism or manipulation of a mate. However, occasionally, the sexes evolve to help increase each other’s fitness during mating, known as sexual cooperation. In spiders, sexual cannibalism of the male by the female is a common occurrence and males of some species have evolved behavioral, morphological, and physiological adaptations to avoid being cannibalized during courtship and copulation. Female Rabidosa rabida, a wolf spider, attack their male partners often during the courtship and copulation process but can be left in a quiescent, or stunned, state post-copulation where they remain unresponsive to external stimuli after the male moves away. Behavioral and microscopy studies with other spiders suggest the quiescent state could be induced by a male produced pheromone from cuticular structures on his legs (transferred by either direct contact or volatile transmission), a chemical in the male ejaculate transferred during insemination, or a component of the male’s venom that he injects in the female. Using R. rabida, I investigated proximate and ultimate questions about male induced female quiescence to avoid sexual cannibalism where I used scanning electron microscopy (SEM), mating trials with modified/ablated males, male homogenate trials, and gas chromatography-mass spectrometry (GC-MS). Specifically, I aimed to locate the organ of compound production (SEM and mating trials), to determine whether the compound was transferred directly or if it was airborne (male homogenate trials), and to identify the compound (GC-MS). I found R. rabida wolf spiders have cuticular structures on their legs that are presumed to be associated with semiochemical emitting organs. Males likely use these organs to induce a quiescent state in their female mates, and females attack the males less often when quiescent. I also found a variety of lipids, hormones, fatty acids, and other hydrocarbon molecules from the two sexes at different life stages with GC-MS. The compound in question was not identified.

Year manuscript completed

2021

Year degree awarded

2021

Author's Keywords

sexual cannibalism avoidance, pheromone, quiescence, manipulation, sexual conflict, sexual cooperation

Thesis Advisor

Laura Sullivan-Beckers

Committee Member

Oliver Beckers

Committee Member

Sterling Wright

Committee Member

Michael Flinn

Committee Member

Bikram Subedi

Document Type

Thesis

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