Aluminium toxicity induced poikilocytosis in an air-breathing teleost, Clarias batrachus (Linn.)

The present study was undertaken to assess the toxicity of acid alone and two different sublethal concentrations of aluminium, (25% and 75% dose of 96 hr LC50 value in acidified soft water of pH 5) on red blood cells of a stenohaline catfish, C. batrachus for an acute exposure of 5 days. The scanning electron microscopic studies on all the three treated groups revealed several kinds of erythrocyte alterations and modifications with abnormal morphology. These included abnormal surface-wrinkling accompanied with excessive roughness on the membrane, erythrocytes with surface granulation in higher dose and finally the appearance of morphologically abnormal forms, the codocyte (target cell) and the stomatocyte. The results suggest that abnormality in the shape of erythrocytes could be linked to altered surface membrane area to volume ratio, decrease in cytoplasmic volume owing to reduced Hb content or increase in the amount of water content within the cell resulting from osmotic disequilibrium. In this context, the abnormal surface membrane morphology could be attributed to cytoskeleton fragility and defects in structural proteins. Further, the acid group exhibited a striking behavior of cellular adhesion and bonding to adjoining cell surfaces, culminating in several bunches which thereby reduces the surface area for gaseous exchange and could produce blocking effect while flowing through microcirculation.

Electron microscopic studies of the corpuscles of Stannius of an airbreathing teleost (Heteropneustes fossilis)

The ultrastructure of the corpuscles of Stannius (CS) of Heteropneustes fossilis reveals a homogenous cellular composition characterized by only one cell type, with large secretory granules and abundant ribosomal endoplasmic reticulum. These cells are comparable to the type 1 cell described in the CS of other teleosts; type 2 cells, whose presence is ubiquitous in the CS of freshwater species are absent in H. fossilis. Our data on the CS of H. fossilis demonstrate that not all freshwater species possess type 2 cells in their CS and these are not essential for life in freshwater