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Thesis Abstract – Garlick-Ott (2018)

Title:

Factors shaping gender role adoption by the freshwater hermaphrodite snail Physa acuta

Author and college:

Kay Garlick-Ott, Pomona College

Date:

April 2018

Degree:

Bachelor of Arts in Biology

Advisor:

Jonathan Wright, Department of Biology, Pomona College

Abstract:

Differential reproduction investment has often been used to explain patterns sexual selection, even for simultaneous hermaphrodite species. Most of the classic demonstrations of this theory assume asymmetrical investment, in which eggs are more costly than sperm and thus females will invest more into a given gamete than males will. It has become clear in more recent studies that the effect of differential reproductive investment (parental investment theory) is more nuanced than previously thought. Simultaneous hermaphrodites are particularly interesting case studies because researchers can evaluate allocation decisions in real time. In some species, one gender role is preferred over the other. In others, traits of the individual, such as mating history, size, or condition are the most important comparative features to consider when predicting decisions made during copulation. Less attention has been given to the importance of environmental factors, like temperature, on these mating systems. Using Physa acuta, gathered from a freshwater pond in Southern California and isolated in aquaria, mechanisms of mating and several factors including temperature were addressed. At higher temperature, mating duration and frequency decreased; however latency to copulation and reciprocity were unaffected. The precise impact of temperature on P. acuta reproduction requires further analysis. Three additional hypotheses were examined: Gender role 1) is size-dependent, 2) is determined by mating history, 3) appears random. Gender preference was not found to be size-dependent, perhaps due to reduced asymmetry of parental investment into male and female gender role adoption. The precise impact of mating history on gender role remains unclear; however, increased isolation time reduced snail proclivity to mate. As such, mating appeared random, perhaps because of population density in situ. Some recommendations were made for future experimentation.

For more information:

Contact Jonathan Wright – Jonathan.Wright@Pomona.edu