Review Article

Clot Formation in the Sipunculid Worm Themiste petricola: A Haemostatic and Immune Cellular Response

Figure 3

(a) Flow cytometry of coelomic cells. Forward light scatter (FSC) versus side light scatter (SSC) dot plot of a sample harvested in EDTA-containing saline. The cluster of LGLs is indicated by the arrow. The large cluster in lower-right position corresponds to haemerythrocytes and large hyaline amebocytes and accounts for more than 90% of all cells in the sample. (b) A similar dot plot corresponding to coelomic fluid from another worm harvested in Ca++ containing saline. The sample is depleted of LGLs due to activation, adhesion, and exclusion of the clotted cells by filtration through a 30 μm mesh. (c) The non-clotting haemerythrocytes (arrows) are the most abundant cells in the coelomic fluid, have a characteristic biconcave disk shape, often have a single large acid vacuole, and are red coloured due to the presence of the respiratory pigment haemerythrin. Bar 15 μm. (d) Large hyaline amebocytes (LHA) also have a single or a few large acid vacuoles and are actively phagocytic. In the photograph LHA can be observed with DAPI-stained bacteria ingested within a large acid vacuole (arrows). Small granular leukocytes (SGLs) are very active phagocytes. The cytoplasm of SGL in the figure is seen densely packed with phagocytosed DAPI-stained bacteria (phase contrast and fluorescent images were digitally overlaid). Bar 15 μm.
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