Effects of exposure to overcrowding on rodlet cells of the teleost fish Dicentrarchus labrax (L.).

Farmed fish are usually exposed to routine procedures which have strong effects
on stress responses. Rodlet cells may represent an useful biomarker for studies on the
presence of stressors in aquaculture. This work focused on the localization of rodlet cells by
light and electron microscopy in gills of sea bass (Dicentrarchus labrax) subjected to
different conditions of overcrowding. In general, a significant increase in number of rodlet
cells has been observed in all animals subjected to overcrowding stress. In gills of control
group rare rodlet cells were detected at the level of both primary and secondary lamellae,
whereas in stressed group clusters of rodlet cells have been found in the epithelium of
primary and secondary lamellae indicating that these cells are influenced by stocking
density.