ULTRASTRUCTURAL ANALYSIS OF THE DIGESTIVE GLAND OF THE LOBSTER HOMARUS-GAMMARUS - ROLE OF VARIOUS CELL-TYPES IN DIGESTIVE PROCESSES

An ultra-structural study is realised on the digestive gland of the lo bster Homarus gammarus. This work shows the presence of five cellular types, four of them being involved in the digestive processes. One typ e (E-cell) has embryonic characteristics and differentiate, along dige stive cycle, into F-cells or R-cells. F-cells appear to play a role in secretory processes, whilst R-cells are responsible for resorption an d long-term retention of nutrients. Only one type (B-cell) is involved in nutrient incorporation and digestion. The fith cellular type are i n fact blood cells, which penetrate into hepato-pancreatic tissue and act as the vertebrate macrophage cells.