A Methodology for Determining Morphological Variation in the Gonopodium in Livebearing Fishes of the Genus Gambusia
Date
2008-04-26
Authors
Stoops, Stacy
Deaton, Ph.D., Raelynn
Journal Title
Journal ISSN
Volume Title
Publisher
Sam Houston State University. Elliott T. Bower's Honor College
Abstract
Description
Mosquitofish are a model system to study sexual conflict, because males of all sizes use forced copulations to mate with females. The intromittent organ, or gonopodium, of the male also is equipped with hooks on the tip, further suggesting a potential role for sexual selection via decreased female fitness. Currently, we are investigating the morphology of the gonopodium, coupled with the forced mating by males to see if this resulted in decreased female fitness via increased tissue damage. The morphological variation in the gonopodium may be related to the strength of sexual selection on the gonopodium itself, which has been shown to be a trait selected for by female mosquitofish (Langerhans et al. 2005). In this study, we collected two species of mosquitofish (G. affinis and G. geiseri) from several different populations throughout Texas in order to test for interpopulation, intrapopulation, and interspecific variation in gonopodial morphology. We predict increased morphological variation across populations of G. geiseri (spring dwelling) than G. affinis (throughout rivers). These findings would support that gonopodial variation may be under sexual selection, and may result in reproductive isolation across disjunct populations of mosquitofish. In order to test our predictions, using 30 males from each population, we measured male body length and gonopodial length, removed gonopodia, and developed a methodology for measuring morphological variation of gonopodia using scanning electron microscopy.
Keywords
Reproduction, Fishes--Spawning, Gambusia geiseri, Gambusia affinis, Mosquitofish