Changes in RNA and oxidative enzymes in Nephelopsis obscura (Erpobdellidae) as indices of environmental stress

Abstract

Low salinity concentrations (1.25 and 2.5 ppt), starvation (1–4 weeks), and temperature (15 °C) produce no changes in the acridine orange – RNA fluorescence of intestinal and tegumentary epithelial cell cytoplasm of Nephelopsis obscura. However, after exposure to 5.0 ppt salinity, or starvation for 5 weeks at 20 °C, ribosomal fluorescence becomes less intense and peripherally redistributed. The large, granular, orthochromatic mucus-secreting cells increase in number with increasing salinity and starvation, and glycogen increases in the muscular and epithelial layers. Nephelopsis obscura exposed to 5.0 ppt salinity show histochemical clumping of mitochondrial oxidative enzymatic activity in degenerating myofibres. Collagen and muscle proteins decrease with increasing salinity and starvation. Changes in oxidative enzymatic activity and RNA synthesis may serve as cytological markers of environmental stresses.