Phagocytic and enzymatic activities of cells and urn cell complexes in the coelomic fluid of the marine worm Sipunculus nudus (Sipuncula)

摘要

Particulate components of the coelomic fluid of the marineudworm Sipunculus nudus were studied by light microscopy andudtheir phagocytic and enzymatic activities examined. Coelomocytesudinclude haemerythrocytes (about 90%), granulocytes and hyalinocytesud(about 9%). In addition, multicellular structures, i.e., urn celludcomplexes are found with low frequency (about 1%). Haemerythrocytesudare nucleated cells, containing the respiratory pigmentudhaemerythrin, which show neither phagocytic nor enzymatic activities.udGranulocytes and hyalinocytes (about 7% and 2% of totaludcoelomocytes, respectively) may be distinguished into two differentudsubpopulations, small and large cells, which may appear asudround or amoeboid. Small cells appear positive to the anti-CD34udantibody for stem cells. The present study demonstrated that bothudcirculating granulocytes and hyalinocytes represented mainudphagocytes, since they were able to recognise and engulf yeastudcells in vitro and contain inducible hydrolytic and oxidative enzymes.udIn addition, both phagocytes produced superoxide anion,udand the neutral red retention suggested that granulocyte granulesudwere lysosomes. The phagocytic ability of urn cell complexes appearsudcontroversial: their ciliated basal cells can trap numerousudyeast cells and show positivity for some hydrolases, but evidenceudof engulfment has never been observed. Lysozyme-like activityudwas found in coelomocyte lysate and to a lesser extent in cell-freeudcoelomic fluid.