Figure 4.

Midgut of spider mite. (A–C) Serial sagittal sections of spider mite female progressing from outside part of the body (A) showing lateral caecal pouches (i–iii) to the middle (C) where posterior midgut (pm) becomes visible. Red arrowheads point to the ventricular epithelium at cranial caeca and ventriculus (v). Blue arrowheads point to the thin single-layered squamous cells that lack microvilli projections at the dorsal and posterior region of the posterior midgut, DE. r, rectum. (D–F) Transverse sections through region of cranial caeca (c1), ventriculus (v), and anterior portion of posterior midgut (pm). (G) Detail of thin dorsal ventricular epithelium (red arrowheads) which transitions to cuboid generative cell (GC) epithelium anteriorly. (H) Detail of thin ventral ventricular epithelium (red arrowhead) adjacent to silk gland (sg) and ovary (ov). (I) Representative transverse section of mite digestive system showing generative cells (GC) of midgut epithelium, large cells (LC) of midgut epithelium adjacent to posterior midgut (pm), and microvilli cells (MC) of posterior midgut. (J) Large cells (LC) of midgut epithelium opposite of microvilli cells (MC) of posterior midgut epithelium. Yellow arrowhead points to basement membrane. (K) Transverse section of LR White plastic embedded and Toluidine Blue stained spider mite. (L) Large cells (LC) of midgut epithelium opposite of microvilli cells (MC) of posterior midgut epithelium. (M) Longitudinal section through ventriculus (v), midgut and posterior midgut (pm) stained with hematoxylin and eosin. (N) Detail of the interface between LCs of midgut and MCs of posterior midgut. Basement membrane (yellow arrowhead) is very well defined in this preparation. Notice the immediate change of cell types in both midgut and posterior midgut epithelia as two become separated in the posterior region (blue arrowheads). Scale bars: (A–C): 100 μm; (D–F): 50 μm; (G,H): 20 μm; (I): 50 μm; (J): 10 μm; (K): 30 μm; (L): 10 μm; (M): 100 μm; (N): 20 μm.