Fig. 5

a Backscattered electron SEM images (with inverse contrast) of a thin section longitudinal to the gill filament close to the marginal food groove (at the top, not visible). The collagenous structure [cs] supporting the hemolymph vessel of the epithelium, the smooth basal membrane [bm], and hemocytes [h] are shown. b, c Higher magnification images of the squares shown in (a). A lobed hemocyte in the central hemolymph shown in (b). Large vacuoles, cs and bm are shown in (c). Three types of cells are indicated, types I and II with a dark nuclei, and the type III with a bright nucleus. The filled arrowheads indicate the microvilli on the apex of cells of type II. The lfc that arise from the cells of type I are also shown