Meeting Abstract
Endocrine disrupting chemicals (EDCs) are globally ubiquitous in aquatic systems. Chronic exposure to EDCs can disrupt endocrine functions and cause reproductive impairment in aquatic species. Western mosquitofish (Gambusia affinis) are an ideal model species for EDC exposure studies because they are distributed globally in surface waters, are sexually dimorphic and they exhibit specific shifts to secondary sex characteristics in response to xenoestrogens. Less is known about whether exposure affects other growth parameters and whether there are population differences in response to exposure. We hypothesized that fish body shape differs between populations and in response to exposure to estrogenic compounds. We collected G. affinis from each of two sites differing in their chemical profiles. Fish from each site were exposed in water from their collection sites to 1 nM ethynylestradiol (EE2) in 0.0002% ethanol (EtOH) or to vehicle. We used geometric morphometric analysis to define morphological landmarks of bodies and gonopodia and Procrustes superimposition to exhibit the variation between the four groups. Canonical variate analysis revealed significant site-related body shape differences between populations, and significant differences between treatment site animals in response to EE2 treatments, with greatest body changes in basal gonopodial width and centroid shape. These results suggest that a genetic bottleneck in fish collected from the spring may have resulted in selective forces that acted differentially on shape between the two populations and limited capacity to respond to xenobiotic exposure; these shifts in responsiveness to chemical pollution may affect reproductive success and have possible fitness outcomes that differ across populations.
