1 Lack of body shape plasticity in mosquitofish exposed to predatory fish Briana Lindsley, Kaylee Pickwell, Chris Roberts, Katie Bridge, Thomas J. DeWitt Bioenvironmental Sciences, Department of Plant Pathology and Microbiology, Texas A&M University Introduction and Objectives Results (Template Revised Summer 2015) Poster is meant to be flexible with defined/standardized sections. Posters are standardized to 36X36 inches for the symposium. Additional recommendations and required information are indicated within the template. Feel free to change the background colors and or design of the headers as you would like. The idea is to simply use the template to organize your presentation. Each section can be whatever length you find appropriate to fully describe your project. Environmental fluctuation stresses organisms because the consequence of trait variation differs across environmental states. For example, in plants short stems are maladaptive in foliar shade from light competitors but are adaptive in bright light to conserve energy and retain robust architecture. Many organisms facing such tradeoffs across environments have evolved the capacity to alter gene expression and development in such a way as to produce alternative, relatively more adaptive trait values in response to environmental cues, relieving stress as the biotic or abiotic environment shifts. Environment-dependent development is termed phenotypic plasticity or “plasticity” (1). One aspect of the environment that can fluctuate is the presence or abundance of predators. Predator-induced phenotypes are common in plants and invertebrate animals, but are less common for vertebrates. Our study organism, mosquitofish (Gambusia affinis) is known to be under strong natural selection for a fast-swimming morphology in the presence of predatory fish such as bluegill sunfish (2). Previous work demonstrates the fast-swimming morphology is under at least partial genetic control (2), but it is unknown if plasticity also plays a role in the body shape differentiation seen in natural populations of mosquitofish. We therefore conducted an experiment to test whether body shape in mosquitofish was responsive to the presence of bluegill (Lepomis macrochirus) during development. Body shapes of mosquitofish from the predator presence and absence treatments were similar with a small but nonsignificant margin of difference (Table 1). Because the P-value was marginally significant, further study and some scrutiny of the nature of the effect, in case it proves to be real, is warranted. The shape difference apparent between treatments involved mosquitofish raised with bluegill having an upturned snout, lower eye position and elongated posterior thrust generating region of the body (Fig. 2). Table 1. MANCOVA results for the effects of size and            fish on body shape in mosquitofish. Source F dfnum dfdenom P Size 5.20 16 63 <.0001 Fish 1.58 0.103 no-predator shape possible bluegill-induced shape Fig. 2. Albeit only a suggestive (marginal but not significant) result in our study, shown is the shape visualization for mosquitofish raised with and without bluegill. Methods Mosquitofish (Gambusia affinis) were caught in Hensel Park and behind the Horticulture building on Texas A&M campus. Pregnant females were placed in holding tanks with breeding traps and allowed to deliver young, which were subsequently used for the experiment. Newborn mosquitofish were reared for 63 days in tanks containing bluegill sunfish or no sunfish. The setup included three tanks of each treatment and each tank held 12 mosquitofish isolated in plastic cups that precluded predation. Mosquitofish body shape was measured by digitizing 10 landmarks, as per Figure 1, on each fish and calculating size and shape variables, all using TPS software (3). Multivariate analysis of covariance (MANCOVA) was run to find the p-value indicating whether the experimental treatment produced a significant result. Discussion & Conclusions The marginal difference in body shape between mosquitofish raised with or without bluegill is perplexing. Plasticity evolves in response to variable environments (1), yet bluegill once present in a mosquitofish population probably do not fluctuate in terms of presence, and perhaps not meaningfully in terms of abundance. So lack of plasticity could fit the natural history of the system. But negative results are hard to interpret. The predator effect was marginally significant, so it is possible there is in fact plasticity. At our sample size, plasticity would have to be a weak effect not to have presented here. It is compelling however, that the nature of the shape difference observed, significant or marginal, is parallel to that found across natural mosquitofish populations with or without bluegill. Given that a genetic contribution to population differences in body shape has been reported (2), and given the marginal result for plasticity, we conclude that the majority of predator-associated morphology observed in the field is due to genetic population differentiation, with little or no plasticity. Fig. 1. Landmarks used to assess body shape of mosquitofish. References Acknowledgements Phenotypic Variation from Single Genotypes. (2004). In T. DeWitt & S. Scheiner (Eds.). Phenotypic Plasticity: Functional and Conceptual Approaches (p. 2). New York, New York: Oxford University Press. Langerhans, B., & DeWitt T. (2004). Predator-driven phenotypic diversification in gambusia affins. Evolution, 58(10), TPS software is available at: We thank the BURS Program that enabled funding for research. Sponsors for high impact experiences for BESC and the BESC poster symposium include the Department of Plant Pathology and Microbiology,  the College of Agriculture and Life Sciences, the Office of the Provost and Executive Vice President for Academic Affairs.