Figure 4.

Digestive cell types in animals. Representative phyla are named (blue boxes) and ordered according to currently widely used phylogenetic trees (Peterson and Eernisse 2016; Kocot et al. 2017; Giribet and Edgecombe 2017) as indicated by blue lines. For each phylum, colored icons in right gray box symbolize major cell types forming the epithelium of the mid-intestine, as explained in framed box at upper right of figure. Nutrient absorption by enteric phagocytes described in the literature can be tentatively assigned to two types: Type A (orange) represents “canonical” phagocytosis, where entire cells or large particles are taken up; type B (yellow) describes a process where mostly smaller particles are taken up into endocytic vesicles that secondarily fuse into large phagosomes. Left grey boxes show different types of apical specializations (cilia, microvilli, dense microvilli organized as brushborder) of enteric phagocytes. For references of publications documenting digestive cell types, see Table 1.