A MORPHOMETRIC AND STEREOLOGICAL ANALYSIS OF ULTRASTRUCTURAL-CHANGES IN 2 SCENEDESMUS (CHLOROCOCCALES, CHLOROPHYTA) STRAINS SUBJECTED TO DIESEL FUEL-OIL POLLUTION

Morphometric and stereological analysis was used to study ultrastructu ral changes induced in two Scenedesmus strains by oil pollution. The s trains exhibited quite different susceptibilities to aqueous fuel oil extract (AFOE): Scenedesmus quadricauda (Turpin) Brebisson G-15 was re sistant, but Scenedesmus microspina Chodat B2-76 was sensitive to a hy drocarbon concentration of c. 50 ppm. Both strains were grown in a bat ch culture system for 7 d on AFOE, after which they were analyzed morp hometrically. Circumferences of the cells and their components were me asured with a digitizer; the mean surface (S) and the mean number ((N) over bar) of cell component profiles and the relative volume (V-v) an d surface density (S-v) of the organelles were then calculated. The re sults indicate that the S of S. microspina cells exposed to AFOE was a pproximately twice that of the control cells, whereas (S) over bar of S. quadricauda cells did not change. Moreover, the cell components of S. quadricauda underwent far fewer changes than did those of S. micros pina. AFOE caused the cells of both strains to become vacuolated, but to different extents. The V-v of the chloroplast and the pyrenoid decr eased, but V-v of the plastoglobuli within the chloroplast increased. The V-v of S. microspina mitochondria increased markedly, whereas in t reated S. quadricauda cells, the mitochondrial V-v did not change, alt hough their S, did decrease significantly. The relative volumes of the cells' nuclei increased in S. quadricauda but decreased in S. microsp ina. Though the mean volumes and surfaces of the microbodies were larg er in both strains, the changes were more clear-cut in S. quadricauda.