Figure 5.

Schematic drawings of enteric phagocytes in representative phyla. Organelles of she phagosome/lysosome system are differentially rendered in yellow (apically located pits, endocytic vesicles, phagosomes), orange (phagolysosomes), blue (lysosomes), and violet (residual bodies; see bottom right of figure). a Phagocytes in platyhelminths (Dugesia gonocephala; from Garcia-Corrales and Gamo 1988, with permission). b Gastrodermal cell types in cnidarians (Tripedalia cystophora; from Chapman 1978, with permission). Numbers refer to phagocyte (1), secretory (spumous) cell (2), neurosecretory cell (3). c Choanocyte in sponges (Ephydatia fluviatilis; from Weissenfels 1976, with permission). Enteric phagocytes in (a-c) perform “canonical” phagocytosis, whereby large food particles are surrounded by lamellipodia and drawn into large apical phagosomes. Panels of middle row (d-g) show different scenario, where food particles and macromolecules are endocytosed into small endocytic vesicles which, together with lysosomes, merge into larger phagolysosomes. This has been described, among others, for chelicerates (d; Hyalomma asiaticum; from Coons and Alberti 1999, with permission), ascidians (e; generic; from Burighel and Cloney 1997, with permission), chaetognaths (f; Tenuisagitta setosa; from Shinn 1997, with permission) and molluscs (g; Mya arenaria; from Pal 1972, with permission). h A similar type of endocytosis has also been described and illustrated for absorptive enterocytes of newborn mammals by (Rattus norvegicus; Wilson et al. 1991, with permission). Asterisks and grey arrows in panels (a) and (d) indicate time sequence, with cell marked by asterisk presenting morphology prior to food uptake, followed by later stages.