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United States Department of Agriculture

Agricultural Research Service

Atlas on Ultrastructure of Infective Juveniles of the Soybean Cyst Nematode, Heterodera glycines


Chapter 5—Ultrastructure of Esophageal Gland Secretory Granules in Juveniles of the Soybean Cyst Nematode, Heterodera glycines

Figure Captions

Figure 113. Longitudinal section of Heterodera glycines J2 at feeding site at 3 days after inoculation of 'Lee' soybean roots. Stylet (St) is retracted, and a feeding plug (FP) fills stylet entry point. Ovate body in host cytoplasm is secretory product of the nematode that may function as a feeding tube (FT). Nematode shows an early stage of growth as indicated by thickening of hypodermis (H) and stretching of the hemidesmosomes (hd). Cuticle (cu) has uniform layer of fibrillar material oriented perpendicular to surface. Ac, amphidial cilia; CW, cell wall; Pm, stylet protractor muscles; Sm, somatic muscles; SW, stomatal wall; Syn, syncytium. Bar=1.0 µm.

Figure 114. Longitudinal section through lip region. Tangential section through stylet tip (St) shows attached feeding tube (FT) with filamentous internal matrix. Cytoplasm of syncytium (Syn) contains large concentrations of rough endoplasmic reticulum (RER) and mitochondria (Mc). Cell wall (CW) near feeding site shows signs of proliferation. FP, feeding plug; so, stylet orifice. Bar=1.0 µm.

Figure 115. Section of syncytium stimulated by nematode shown in fig. 113. Series of ovate secretion structures in cytoplasm are oblique sections through a sinuous feeding tube (FT) extending into host cell. Stimulated cell of syncytium initially shows accumulation of dense cytoplasm with many free or endoplasmic reticulum-associated ribosomes, plastids, and mitochrondria. Size of vacuoles (Va) depends on cytoplasmic density. CW, cell wall; FP, feeding plug. Bar=1.0 µm.

Figure 116. Section of a syncytium (Syn). Wall perforations (CWO) induced by nematode feeding result in cytoplasmic continuity and multinucleate condition. Calloselike material (Ca) is deposited along intact and fragmented cell walls. RER, rough endoplasmic reticulum. Bar=1.0 µm.

Figure 117. Transverse section through dorsal gland ampulla (DA). Ampulla is distended by accumulation of many secretion granules (SG). Adjacent procorpus tissue (prc) contains many mitochondria and extensive rough endoplasmic reticulum that is associated with stylet protractor muscle system. Dorsal esophageal gland valve (DAv) lies within ampulla cytoplasm close to esophageal lumen (EL). Bar=1.0 µm.

Figure 118. Transverse section through dorsal gland ampulla (DA), showing two types of spherical secretion granules. The electron-opaque, relatively small granules (SG) are similar to granules at extreme anterior of ampulla and in central component of dorsal gland cell. Low-density secretion granules (LSG) are found in dorsal gland extension and in posteriad region of ampulla. They have filamentous or flocculent contents. GlR, glycogen rosettes; prc, procorpus. Bar=1.0 µm.

Figure 119. Enlarged view of metacorporeal sphincter muscle valve, showing closely packed microtubules (Mt) and a neural process (NP) within dorsal gland extension (Dx) surrounded by network of sphincter muscle elements (Spm). These muscle cells and compressed gland extension are supported by membrane junctions that adhere to esophageal lumen wall. Bar=1.0 µm.

Figure 120. Longitudinal section through procorpus-metacorporeal sphincter muscle (Spm) valve, showing tightly packed microtubules (Mt) that control movement of secretion granules (SG) but allow cytoplasmic continuity within dorsal gland extension. EL, esophageal lumen; m, metacorpus; prc, procorpus. Bar=1.0 µm.


Figure 121. Longitudinal section through isthmus-metacorporeal sphincter valve, showing accumulation of secretion granules (SG) in dorsal gland extension. Note absence of secretion granules in region of valve and also dorsal gland extension that traverses the metacorpus (m). i, isthmus; Mt, microtubules; Spm, sphincter muscle. Bar=1.0 µm.

Figure 122. Cross section of dorsal gland extension (Dx) as it traverses anterior region of metacorpus. Electron-opaque, spherical secretory granules (SG) in gland extension are similar to those observed in dorsal gland cell. Esophageal lumen wall (ELW) and border of dorsal gland extension are surrounded by network of membranes (LWM). These lumen-wall-associated membranes lie close to muscle elements of metacorpus. Mt, microtubules. Bar=1.0 µm.

Figure 123. Cross section through sphincterlike muscle (Spm) region at base of metacorpus. Dx, dorsal gland extension; Svx, subventral gland extension. Bar=1.0 µm.


Figure 124. Oblique section through base of metacorpus pump and isthmus, showing difference in secretion granule morphology between subventral and dorsal gland extensions. Sphincterlike muscle serves as isthmus-metacorporeal valve (imV) and appears to regulate movement of secretion granules within dorsal and subventral gland extensions. DSG, dorsal gland secretory granules; SSG, subventral gland secretory granules. Bar=1.0 µm.

Figure 125. Longitudinal section showing a subventral gland ampulla (SvA) with closed subventral gland valve (SAv) and small electron-opaque, irregularly shaped secretion granules (SSG). Posterior metacorpus sphincter valve appears closed, restricting movement of secretion granules of dorsal gland (DSG). These dorsal gland granules are similar to enlarged granules in other specimens (see figs. 117, 118). Dx, dorsal gland extension; imV, isthmus-metacorporeal valve. Bar=1.0 µm.

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Last Modified: 2/6/2002
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