DIFFERENTIATION OF B-CELLS IN THE HEPATOPANCREAS OF THE PRAWN PENAEUS-MONODON

The genealogy of B-cells in the hepatopancreas of decapod crustaceans is still a matter of intense debate. According to widely accepted two-cell-line concepts, B-cells are supposed to originate either from secretory F-cells or absorptive R-cells. These concepts are based on the putative lack of B-cells in the differentiation zone of the hepatopancreas tubules. In the giant tiger prawn Penaeus monodon I could clearly identify differentiating B-cells in that zone by using an ultrastructural distinguishing mark, the apical complex, that is much more sensitive than markers used before. Tracking of this feature from mature B-cells through the differentiation zone up to the embryonic E-cells revealed that B-cells directly originate from E-cells. The recognition of B-cells as a separate cell line calls for a new functional interpretation. Ultrastructural and histochemical data suggest a degrading function. B-cells may clear the hepatopancreas tubules from remnants of digestion in the time span between nutrient absorption and secretion of new digestive enzymes.