Abstract
We examined, from a morphological and ultrastructural point of view, the gill epithelium of Triturus italicus, both in basal conditions and after acute exposure to low pH. Our analysis of gill morphology began with the aim of determining lethal pH levels; we found that the pH value at which 50% of mortality occurs (LC50) is 4.0. We then investigated the effects of the larvae's exposure to a critical value of pH (pH 4.5).
No change was observed in the gill during the first 24βhr. After 48βhr, a cellular response was evident and the gills appeared covered with a dense mucous layer. Observations that were carried out by light microscopy (LM) and electron microscopy, both scanning (SEM) and transmission (TEM), showed considerable histological and ultrastructural changes.
As regards the principal filament, the alterations resulted in the presence of an external keratinized layer. More changes affected the mitochondriaβrich cells (MRCs) in both a qualitative and quantitative way; this cell type shows a wide surface and seems to protrude more than the near pavement cells that, in normal conditions, partially cover the MRCs, thus reducing their external surface. The microvilli were extremely lengthened and often anatomized each other. Changes in the secondary filament affected the thickness of the epithelium, which appeared considerably smaller in the gills of the newts exposed to acid stress. The ciliated cells appeared to be more numerous than in the control specimens and the MRCs showed a widening of the apical surface. J. Exp. Zool. 303A:946β957, 2005. Β© 2005 WileyβLiss, Inc.