Confocal laser scanning fluorescence microscopy of Botryococcus alginite from boghead oil shale, Boltysk, Ukraine: selective preservation of various micro-algal components

Abstract

Confocal laser scanning fluorescence microscopy (LSM) has exceptional potential for resolving micrometer scale morphological details within fluorescing macerals (e.g. alginite) of hydrocarbon source rocks and oil shales. This investigation of well preserved Botryococcus alginites from a Paleogene boghead oil shale from central Ukraine clearly illustrates that LSM can effectively resolve microalgal cellular organization. A dominance of highly resistant, outermost cell walls in Botryococcus confirms that selective preservation was an effective process during kerogen formation. Three dimensional serial section compilations of images taken through Botryococcus alginites reveals a number of cellular features including: (i) micro-layering within resistant outer cell walls; (ii) preservation of resistant, very thin, outer walls of apical cells and; (iii) stacks of successive thimble-shaped layers and funnel-shaped cups which comprise the resistant stalk framework of fossilized compound colonies. LSM also discloses preservation of pairs of ‘reproducing’ Botryococcus cells consisting of outer resistant walls enclosing mainly unstructured, granular organic matter in the ‘cell contents region’. Some serial images from these areas do, however, show evidence for cellular organization and possible selective preservation of possible resistant biomacromolecules derived from aplanosphores or zoospores.