Fig 1.
Anatomical view of the alimentary canal of G. gratiosa. Scale bar = 5 mm.
Fig 2.
General organization of the midgut in G. gratiosa.
(A) Longitudinal section of the gastric caeca. (B) Transverse section of the ventriculus. (C) The region delimited by the rectangle in (B). (D) Regenerative cells under TEM. pm: peritrophic membrane; ep: epithelium; bl: basal lamina; mu: muscle layer; ef: epithelial fold; rc: regenerative cell; pc: principal cell; ec: endocrine cell; lmu: longitudinal muscle; L: lumen. Scale bars: (A) = 1 mm; (B) = 200 μm; (C) = 20 μm; (D) = 1 μm.
Fig 3.
The apical region of principal cells from four parts of the midgut of G. gratiosa, as observed by TEM.
(A) The gastric caeca. (B) The anterior ventriculus. (C) The middle ventriculus. (D) The posterior ventriculus. sv: secretory vesicle; mv: microvilli; sg: secretory granule; ld: lipid droplet; fm: filaments; ls: lysosomes; m: mitochondria; SER: smooth endoplasmic reticulum. Scale bars: (A) = 2 μm; (B) = 1 μm; (C) = 2 μm; (D) = 2 μm.
Fig 4.
TEM photographs of various-sized lysosomes, multivesicular bodies (MVBs), autophagosomes and a few lipid droplets.
(A) MVB endocytosed by a lysosome. The inset shows the dilation of the MVB in the white rectangle. The MVBs contain dense material, similar to a secretory vesicle. (B) Lipid droplets hydrolyzed by a lysosome. (C) The MVBs contain dense material, which appears identical to the contents of secretory vesicles. (D) An autophagosome containing cytosolic components in the middle zone of a principal cell. ls: lysosome; MVB: multivesicular body; ld: lipid droplet; m: mitochondria; g: Golgi apparatuses; li: lipid; au: autophagosome. Scale bars: (A) = 1 um; (A, inset) = 200 nm; (B-D) = 1 μm.
Fig 5.
The middle zone of principal cells of the midgut of G. gratiosa, TEM.
(A) The gastric caeca. (B) The ventriculus. n: nucleus; RER: rough endoplasmic reticulum; g: Golgi apparatuses; v: vesicle; trs: tracheoles. Scale bars: (A) = 1 μm and (B) = 500 nm.
Fig 6.
The basal region of principal cells from four parts of the midgut of G. gratiosa, TEM.
(A) The gastric caeca. (B) The anterior ventriculus. (C) The middle ventriculus. (D) The posterior ventriculus. ld: lipid droplet; trs: tracheoles; bl: basal lamina; m: mitochondria; trc: tracheolar cell; cmu: circular muscle; lmu: longitudinal muscle; tr: tracheas; n: nucleus. Scale bars: (A and D) = 3 μm; (B) = 2 μm; (C) = 1 μm.
Fig 7.
Cell junctions of principal cells and the distribution of tracheoles in the midgut of G. gratiosa, TEM.
(A) Desmosomes and septate junctions with deep interdigitations of an adjacent cell. (B) Tracheoles in the apical region of a principal cell. (C) Tracheoles in the middle region of a principal cell. ds: desmosomes; sj: septate junction; m: mitochondria; trs: tracheoles; mv: microvilli; RER: rough endoplasmic reticulum. Scale bars: (A) = 300 nm and (B and C) = 1 μm.
Fig 8.
Fine structure of the secretory devices of the midgut of G. gratiosa.
(A) Secretory devices in the gastric caeca, SEM. (B) Secretory devices in the ventriculus, SEM. (C) Merocrine secretion, TEM. (D) Apocrine secretion, TEM. (E) Holocrine secretion, TEM. bsb: bulb-shaped bubble; csb: cylindrical-shaped bubble; sg: secretory granule; mv: microvilli; n: nucleus. Scale bars: (A) = 2 μm; (B) = 10 μm; (C and D) = 1 μm; (E) = 3 μm.