Clot Formation in the Sipunculid Worm Themiste petricola: A Haemostatic and Immune Cellular Response
Figure 2
(a) A large clot formed by the aggregation of large granular leukocytes (LGLs) is shown entrapping magnetic beads (thick white arrows). These cellular clots are rapidly formed by contact with sea water and may serve a haemostatic purpose precluding loss of coelomic fluid upon body wall injury but may also serve an immune function entrapping foreign agents. The preparation corresponds to a male worm and numerous activated spermatozoids can be seen interspersed all around the microscopic field (thin black arrows). Bar 50 μm. (b) A large granular leukocyte (LGL) is shown in resting state as observed when coelomic fluid is harvested using EDTA-containing saline solutions. Bar 15 μm. (c) The presence of sea water or Ca++ containing saline induces massive morphological changes that include the extrusion of filopodia. Bar 15 μm. (d) Activated LGLs adhere to each other to form a clot but may also adhere firmly and spread over glass surface acquiring very peculiar shapes. However, cell death and cytoplasmic disintegration of glass-adhered LGLs ensues within minutes, and samples must be fixed quickly in order to be observed microscopically. Phase contrast image digitally overlaid to a fluorescent image of a DAPI-stained preparation. Bar 15 μm.
