Resistance of Biomphalaria alexandrina to Schistosoma mansoni and Bulinus truncatus to Schistosoma haematobium Correlates with Unsaturated Fatty Acid Levels in the Snail Soft Tissue

Figure 6

Histological transverse sections showed normal cephalopodal tissue structure of naïve B. truncatus snails maintained on algae or lettuce, respectively (a, b). (c, d) are of infected snails showing live mother sporocysts with normal development pattern; some of them contain single sporocyst cluster (arrowhead), and others contain multiple sporocyst clusters (twin thick arrows). All sporocysts contain viable germinal cells with nucleoli; the vacant space (dashed arrow) between the sporocyst and the tegument of the mother sporocyst also appears normal. Regarding resistant snails, cephalopodal tissue shows the sporocysts losing their characteristic cluster-like shape and dissolution of the surrounding tegument (dashed arrow), leading to dispersion of germinal cells (arrowhead) (e). The mantle collar region displays sporocycts have lost their cluster-like shape, and no viable germ cells are observed (thick arrow). Note, the negligible presence of hemocytes (thin arrow) and fibroblasts lamination (arrowhead) surrounding the sporocysts (f).

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(b)

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(f)