Meeting Abstract
Across the fish genus Poeciliopsis there are varying degrees of placentation, determined by the amount of continued maternal nourishment provided to the embryo after fertilization. This placenta variation can be studied using a morphological approach to examine the placenta structures involved in maternal-fetal nutrient exchange. Possible comparative features include the maternal follicle that surrounds the developing embryo, the amount of yolk present in the yolk sac of embryos, and embryo structures potentially utilized for nutrient absorption. Recent comparative morphological studies in Poeciliopsis have used scanning electron microscopy techniques, finding surface features of the maternal follicle and embryos that vary across species. We present a preliminary histological analysis that compares the gestating ovaries from four different species of Poeciliopsis representing placentation variation. Histological slides were previously prepared from fixed, embedded, sectioned, and hematoxylin and eosin stained gestating ovaries of Poeciliopsis gracilis, P. infans, P. prolifica, and P. turneri. Slides were observed at 40x under light microscopy and digital images were captured using the program Infinity Analyze. We are in the process of creating an extensive digitized collection and panoramic images of entire ovaries. With these panoramas we have begun to grasp a clearer picture of the overall features of the ovary, embryos, maternal tissues and cellular structures. We are currently using these images to determine which ovarian and placenta structures to compare across species. Once determined, future microscopy at higher magnification will enhance our understanding of the evolution of placentation in Poeciliopsis.
