USING INCIDENT LIGHT TO MAXIMIZE RESOLUTION OF STRUCTURE ON DIATOM VALVES WITH A LIGHT MICROSCOPE

Abstract

Siver, P. A.Botany Department, Connecticut College, New London, CT 06320Because of their abundance in a diverse array of aquatic habitats and chemical conditions, and the fact that their species‐specific siliceous outer coverings remain for millennia in sediments, diatoms have become one of the most powerful organismal groups used in the reconstruction of historical environmental conditions. Although SEM is now needed to identify some species, the bulk of the identifications and data collection is still accomplished with a light microscope. In this paper I will demonstrate the use of interference reflection contrast (incident light) for the examination of diatoms that significantly improves the resolution of structural detail. Using incident light one can routinely distinguish between structures close to the theoretical limit of resolution for visible light, and about 70 nm closer together than resolvable with standard transmitted light optics. Examples of how the incident light technique can improve data collection with light microscopy will be given. Most research light microscopes could be easily and inexpensively outfitted to use this technique.