ABSTRACT
Estuarine euryhaline teleosts as reared spotted scat will be continnously encounterd with alterations to water salinities. The aim of the present study was to evaluate osmoregulatory capacity of the spotted scat in response to different salinities. 120 fish were categorized into 4 groups of 30 fish each. The fish were transferred from the freshwater to different salinities [5, 10, 20, and30 g/L] and kept for one month. Tissue sections of the secondary lamella and gill branches were staind using hematoxyline eosin and studied by the light microscope. Transfer from freshwater to different salinities made significant increase [p<0.05] in total chloride cells of the secondary lamella. Furthermore, while chloride cells alterations have been accompanied with decrease in the chloride cell numbers of the lamella such changes made an increase in chloride cell numbers of the gill branches. It can be concluded that the mentioned species has limited osmoregulatory capacity when encountering abrupt salinity changes.
Subject(s)
Animals , Salinity , Chlorides , Gills , FishesABSTRACT
In order to study the role of the kidney in fish osmoregulation, freshwater acclimatized juvenile spotted scat [Scatophagus argus L.] were subjected to four different salinities and observed for histomorphometric changes of the kidney at 1, 2, 10 and 15 days post transfer time points. The overall morphological changes displayed by fish kidney included significant decrease in the density of collecting tubules and glomeruli when subjected to higher salinity levels [10, 20 or 30 g/l] in comparison to proliferated, extensive, dense and muscular ones retained in the kidney of residents in freshwater and also of 5 g/l adapted animals. In conclusion, the observed histomorphological changes in the current study agree well with previously established physiological differences in the function of teleost kidney in freshwater and in the seawater