Male mate preference in the eastern mosquitofish (Gambusia holbrooki)

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Michael Mcmillan (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Katherine Bruce

Abstract: As a live-bearing fish, Gambusia holbrooki offers unique opportunities to study sexual selection. While males of this species invest little time or energy per offspring, sexual selection theory should predict that if a male is presented with two females of differing size, a preference should be shown for the larger of the two females. Evolution should favor the choice of a larger female because of increased brood size, better health, and ability to survive the environment. Only two studies to date have looked at male mate preferences in Gambusia holbrooki, and the results were mixed. In this study, to measure male preference a dichotomous choice test was used with female fish of varying sizes placed in clear containers at opposite ends of an aquarium. The elapsed time a free swimming male spent in “side time” (on same side of aquarium as either female) and “proximity time” (within one male length) was recorded. Experiment 1 looked at male preference for females differing in size by at least 5mm and found that males (n=12) spent significantly more time in close proximity to larger (compared to smaller) females in the first 10 minutes of a 20-minute preference test. The males, however, did not show a significant preference in side time. Experiment 2 sought to increase the size discrepancy between the two females tested and included very large females, as they might provide a supernormal stimulus for the male (n=9). However, the results of Experiment 2 showed no such preference in side time or proximity time. Experiment 3 increased the number of subjects to 27 to provide a more representative sample of female fish a male might encounter in the wild and added a social interaction portion to the testing. Female size differential groupings were broken in to three categories: Small (2-6mm), Medium (8-11mm), and Large (13-17mm). The results of this experiment showed a significant preference for the larger females that was dependent upon the size differential grouping, with proximity time in the medium grouping being most pronounced. In the social interaction portion of the testing, a significant preference was found for larger versus smaller females, but there was not a significant preference found between the size groupings. As predicted by the sexual selection theory, the results of the aforementioned experiments seem to indicate that a male mate preference for larger females does exist, but only within certain parameters.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Arts
Language: English
Date: 2009
Keywords
Courtship in animals , Eastern mosquitofish--Reproduction, Eastern mosquitofish--Research, Eastern mosquitofish--Sexual behavior
Subjects
Eastern mosquitofish -- Research
Eastern mosquitofish -- Reproduction
Courtship in animals
Eastern mosquitofish -- Sexual behavior