Nuclear Morphology and Lysosomal Stability of Molluskan Hemocytes as Possible Biomarkers of Arsenic Toxicity

The frequency of nuclear aberrations and neutral red retention time of hemocytes in the mollusk Lamellidens marginalis were recorded under exposure to sublethal concentrations of sodium arsenite in order to examine the sensitivity and effectiveness of these inexpensive assays for screening the toxicity of As³⁺ in a freshwater ecosystem. A dose and time dependent increase in the density of micronucleated and binucleated hemocytes and gill cells was indicative of the pronounced genotoxic effect of arsenic on this animal. The disruption of intrahemocyte homeostasis imposed by this natural toxicant was evident from a dose and time dependent reduction in the lysosomal stability of the hemocytes of the animal. The tested parameters are indicative of arsenic toxicity in L. marginalis in the freshwater systems of the arsenic affected geographical areas of West Bengal, India.     

Folding of boudinaged layers

The boudinage structure in the Väddö area in Sweden developed during an early isoclinal folding. During a second deformation which deformed the axial surfaces and the limbs of the isoclinal folds, the shapes of boudins were variously modified. The resulting structures include folding of the individual boudins into half-waves, a tile-like piling up of straight or gently folded boudins and arrangement of straight boudins in a herring-bone pattern. Similar structures have been produced experimentally in soft models containing ‘boudins’ of different competencies. The relative importance of the different physical parameters which contribute towards the development of the various structures is examined. In particular, the experiments showed that when the competence contrast between the boudin and the host material was rather small, the shape of the boudins was modified by a second deformation into trapezoidal forms often with flame-shaped projections at the edges. From an analysis of the experimental and natural structures, a set of criteria has been formulated which can be used to identify structures formed by superposed deformations and to give an approximate idea of the competence contrast between the boudin and the host rock during the second deformation.