Prize Poster:Document Sperm Head Morphology Among Fruit Flies in the Genus Drosophila
Pictured : Undergraduate biology major, Stefan Barone and his faculty research mentor, Dr. Valerie Schawaroch.
Stefan's poster was presented at the Metropolitan Association of College and University Biologists (MACUB) meeting. Barone was awarded second prize for his poster and accompanying presentation in the category of undergraduate research at a four year college.
Morphological features (characters) are compared among species to hypothesize their evolutionary relationships. This paper is the first to report on efforts to employ scanning electron microscopy (SEM) to document the ultrastructural morphology of sperm heads among fruit fly species in the genus Drosophila. Previous investigations report that the mature sperm head takes on the form of a “needle-like” structure. However, these studies have utilized bright field, fluorescence, and/or confocal microscopy which lack the fine resolution needed to identify any ultrastructural differences in the surface morphology of sperm heads among species. Representative species within the genus Drosophila were chosen based on their relative taxonomic position and on the fact that their genomes have been sequenced. Mature sperm were collected and fixed in either glutaraldehyde alone or glutaraldehyde followed by post-fixation with osmium tetroxide. The samples were then dehydrated in an ethanol series, critical point dried, sputter coated with gold/palladium, and imaged using a Hitachi S 4700 cold field-emission scanning electron microscope. Images obtained using the SEM provide fine details of surface morphology that may be useful for proposing hypotheses of evolutionary relationships among species.