RODLET CELLS IN THE EPIDERMIS OF FISH EXPOSED TO STRESSORS

Rodlet cells (RC) were detected in the epidermis of carp (Cyprinus car pio) and trout (Oncorhynchus mykiss) exposed to stressors (e.g. acid w ater, heavy metals, thermal elevation, polluted water of the Rhine riv er, water loaded with organic manure, and distilled water), as well as after wounding, These cells were not found in the epidermis of fish k ept under control conditions, thus suggesting that the appearance of R C in the epidermis is stressor-related. Immature RC, resembling mucous cells, were found in deeper epidermal zones while mature RC were foun d close to and at the skin surface, The latter contained several rodle ts embraced within a capsule-like structure composed of filaments, At the skin surface, RC opened the filamentous capsule at the cell apex a nd a cytoplasmic tuft, containing the rodlets, protruded outwards into the surrounding water, Structures which appeared to be free rodlets w ere also observed in the water, near the ridges of the pavement cells. Cytochemical and immunocytochemical study revealed that the rodlets c ontain alkaline phosphatase at their periphery and peroxidase activity at their cores, These enzymes have been previously reported in mucous cells of stressed fish, All together, the location of RC, their struc ture, cytochemistry and direction of migration suggest that these cell s form part of the non-specific defence mechanism of the skin, and pos sibly other epithelial tissues.