Clot Formation in the Sipunculid Worm Themiste petricola: A Haemostatic and Immune Cellular Response
Figure 4
(a) A small clot-entrapping bacteria (arrows). Lysosome rupture, cell death, and nucleic acid degradation occur first in the inner parts of the clot creating a hostile degradative environment for the captured pathogens. Green fluorescence corresponds to viable cells as indicated by fluorescein-diacetate (FDA) probe. The dark area in the centre of the clot is due to the abundance of dead cells which do not retain FDA. Nonclotting phagocytic cells (LHAs and SGLs; shown in Figure 3(d)) are found in the neighbourhood and have an ancillary role engulfing self and foreign material detached from the clot. Phase contrast and fluorescent images were digitally overlaid. Bar 30 μm. (b) The clot hardness is brought by preserving F-actin after death of adhered cells. The insoluble mesh of F-actin is detected by staining with red-fluorescent probe phalloidin rhodamine. Bar 15 μm. (c) Phase contrast image of the clot shown in (b). Bar 15 μm. (d) When particles are injected in vivo, several small clots (arrows) with a size comparable to that of female ovocytes or male clusters of maturing spermatic cells are formed instead of a massive single clot as occurs ex vivo. This may facilitate extrusion of entrapped material through the nephridia. Bar 50 μm.
