Epithelial cell renewal in the digestive gland and stomach of mussels, season, age and tidal regime related variations

Abstract

The natural variability in cell proliferation activity in the epithelium of the digestive gland and stomach was investigated in mussels, Mytilus galloprovincialis (Lmk), of different age and tidal level at different seasons. After treating mussels with the thymidine analogue bromodeoxyuridine (BrdU) for 6 hours, BrdU immunohistochemistry was performed every 2 hours for the next 36. The relative proportion of BrdU positive cells was quantified as BrdU labelling (‰). Marked seasonal differences were recorded in BrdU labelling, with much higher proliferating activity in summer than in autumn and winter. Cell proliferation seemed not to be significantly dissimilar between mussels of different age (size). In contrast, the digestive gland epithelium of mussels from intertidal and subtidal populations differed not only in the levels but also in the pattern of variation of BrdU labelling, which in intertidal mussels appeared to be modulated by photoperiod and tide, unlike in subtidal mussels, in which variations followed a circatidal pattern.