Page Banner

United States Department of Agriculture

Agricultural Research Service

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

 

Chapter 9—Ultrastructure of Intestine of Second- and Third-Stage Juveniles of the Soybean Cyst Nematode, Heterodera glycines

Figure Captions

Figure 179. Diagram of an infective Heterodera glycines J2. Arrows indicate sectors used for diagrams. DA, dorsal gland ampulla; DN, dorsal gland nucleus; IE, intestinal epithelium; GP, genital primordium; m, metacorpus; nr, nerve ring; prc, procorpus; SvN, subventral gland nucleus.

 

Figure 180. Nematode at feeding site showing stylet (St) in contact with feeding plug (FP).

 

Figure 181. Diagram of isthmus region showing triradiate lumen (TL) of esophagus.

 

Figure 182. Diagram showing cross section of esophago-intestinal valve (Eiv) made up of two esophageal cells with apposed noncuticular apical membranes. Esophago-intestinal valve lies in proximity to dorsal gland nucleus (Dn). Dg, dorsal gland.

 

Figure 183. Diagram showing cross section of intestinal epithelium (IE). Intestinal lumen (IL) is lined with microvillilike (MvL) invaginations and surface folds. Enlargements of microvillous invaginations and surface folds sculptured with enteric surface materials (ES) are shown in tangential and cross sections.

 

Figure 184. Intestinal epithelium (IE) displaced by genital primordium (GP). IL, intestinal lumen.

 

Figure 185. Diagram of longitudinal section showing intestinorectal valve (IRv), rectal channel (rC), and anus (an). ADM, depressor ani muscle; IL, intestinal lumen.

 

Figure 186. Longitudinal section of an infective Heterodera glycines J2, showing esophago-intestinal valve (Eiv) and lumen of anterior region of intestine (IL). Lumen is partially blocked by microvillilike (MvL) and related surface folds of lumen membrane. Intestinal epithelial cells contain characteristic lipid droplets (LD). cu, cuticle; Sm, somatic muscles. Bar=1.0 µm.

 

Figure 187. Longitudinal section of an infective J2 showing spatial relationship of (1) the cells of the esophago-intestinal valve (Eiv) with their nuclei and (2) the dorsal esophageal gland with a single prominent nucleus (DN). Tangential section into lumen of anterior intestine reveals one of three membrane junctions (MJ) that join epithelial cells of intestine. IE, intestinal epithelium; IL, intestinal lumen; Dg, dorsal esophageal gland. Bar=1.0 µm.

 

Figure 188. Longitudinal section of J3 at 1 hour after inoculation, showing expanded esophago-intestinal valve (Eiv) and lumen ( IL) apparently filled with ingested host contents. Bar=1.0 µm.

 

Figure 189. Cross section of an infective Heterodera glycines J2, showing a portion of esophago-intestinal valve (Eiv). Closed mode of valve is depicted by unlined noncuticularized membranes (uM) bordered by electron-translucent cytoplasm and supported by membrane junctions. Esophago-intestinal valve is bordered by branch of intestinal lumen (IL), dorsal esophageal gland (Dg), and extensions of subventral glands (Svx). Bar=1.0 µm.

 

Figure 190. Cross section of an infective J2 showing tripartite nature of intestinal epithelium. Intestinal lumen (IL) in its nonexpanded state is delineated by cells joined by two of three membrane junctions (MJ) located at centripetal boundaries of intestinal epithelium. Mc, mitochondria. Bar=1.0 µm.

 

Figure 191. Cross section of Heterodera glycines J2 at 18 hours after inoculation, showing esophago-intestinal valve of nematode located at feeding site. Noncuticularized cell membranes of esophago-intestinal valve are separated by apparent ingested products (ip) from host. Prominent nucleus (N) is typical of cells forming esophago-intestinal valve. Bar=1.0 µm.

 

Figure 192. Cross section of J2 at 18 hours after inoculation, showing region posteriad to esophago-intestinal valve in fig. 191. Open lumen of intestine (IL) is formed by three cells joined at their inner cell boundaries with membrane junctions (MJ). Lumen surface ranges from smooth to irregular with invaginations of portions of lumen membrane, some of which have sculptured surfaces (arrow). Dg, dorsal esophageal gland. Bar=1.0 µm.

 

Figure 193. Longitudinal section through esophago-intestinal valve complex (EvC) and the most anterior sector of intestine of a Heterodera glycines J2 at 2 days after inoculation. Esophago-intestinal valve complex merges anteriorly with cuticular esophageal lumen lining (CEL), which is supported by network of membrane junctions (MJ). Esophago-intestinal valve complex is surrounded by intestinal epithelium (IE). IL, intestinal lumen.

 

Figure 194. Cross section of J2 at 2 days after inoculation, showing intestinal lumen (IL) just anterior to rectal valve. A muscle fiber (rm) is related to other muscle elements that are part of intestino-rectal system. IE, intestinal epithelium. Bar=1.0 µm.

 

Figure 195. Section through J2 at 2 days after inoculation, showing rectal valve of same specimen described in figs. 193 and 194. Network of membranes and membrane junctions (MJ) constitutes parts of intestino-rectal valve. Muscle elements (rm) in three of four corners of micrograph are part of intestino-rectal muscle system. Bar=1.0 µm.

 

Figure 196. Section through terminus of esophageal lumen cuticle (CEL) of a Heterodera glycines J2 at 3 days after inoculation. Lumen is closed with lumen wall contacting membrane junctions (arrows) at four points. Bar=1.0 µm.

 

Figure 197. Transition between cuticular esophageal lumen (CEL) and membranous portion of esophago-intestinal valve (Eiv). This is same specimen as shown in fig. 196. N, nucleus of esophago-intestinal valve cell. Bar=1.0 µm.

 

Figure 198. Cross section of esophago-intestinal valve (Eiv) of fig. 196 with various gradations of membrane junctions and noncuticularized cell membranes. Anterior extremity of intestinal lumen (IL) is adjacent to esophago-intestinal valve. Dg, dorsal esophageal gland; MvL, microvillilike membrane folds. Bar=1.0 µm.

 

Figure 199. Cross section of anterior intestinal region of Heterodera glycines J2 at 3 days after inoculation. Intestine lies adjacent to esophageal glands and occupies about half the cross-sectional area of the nematode. Individual epithelial cells are not clearly defined by membrane junctions as noted among infective juveniles. Lumen of intestine (IL) is irregular and blocked with numerous microvillilike membrane folds. Epithelial cells contain prominent lipid droplets (LD) and numerous glycogen rosettes (GlR). Dg, dorsal esophageal gland. Bar=1.0 µm.

 

Figure 200. Cross section through midsection of J2 at 3 days after inoculation. Intestinal epithelial cells form a partially collapsed intestinal lumen with microvillilike membrane folds (MvL). Epithelial cells contain densely stained lipid droplets (LD) and numerous glycogen rosettes (GlR). Intestinal epithelium (IE) occupies about half the cross-sectional area of the nematode and is bounded on each side by hypodermal (H) tissue. Bar=1.0 µm.

 

Figure 201. Enlargement of microvillilike membrane folds within intestinal lumen of J2 at 3 days after inoculation. Microvillilike membrane folds (MvL) vary widely in dimensions as they form elongated evaginations of apical membranes of intestinal epithelial cells. Surfaces of microvilli are sculptured with an enteric coating (EC) when viewed in cross, longitudinal, and tangential sections. L, central lumen. Bar=1.0 µm.

 

Figure 202. Enlargement of sector of lumen of J2 at 3 days after inoculation, showing enteric coating (EC) on surface of microvillilike membrane folds (MvL). Longitudinal and cross sections of microvillilike membrane surfaces show uniformity of projections made by enteric coating. GlR, glycogen rosettes; IL, intestinal lumen. Bar=0.5 µm.

 

Figure 203. Cross section of central region of intestine of Heterodera glycines J2 at 4 days after inoculation, showing three-celled structure of intestinal epithelium (IE) indicated by membrane junctions (MJ) near surface of central lumen (IL). Lipid droplets (LD) occur throughout intestinal epithelium. Cell membranes extend from membrane junctions to periphery of intestine. Bar=1.0 µm.

 

Figure 204. Cross section of posteriad region of J2 at 4 days after inoculation, showing bilayered structure of intestine. Lipid droplets (LD) and glycogen rosettes (GlR) are abundant in epithelium (IE). Microvilli are varied in morphology within expanded intestinal lumen (IL). Sculpturing from enteric coating materials occurs on microvillilike (MvL) and other surface areas within lumen. H, hypodermis; MJ, membrane junction. Bar=1.0 µm.

Figure 205. Heterodera glycines J2 at 4 days after inoculation, showing enlargement of fig. 204 with uniform surface sculptures of an enteric coating (EC) on microvillilike and other membrane surface folds. IL, intestinal lumen. Bar=1.0 µm.

Figure 206. Cross section of Heterodera glycines J3 at 5 days after inoculation, showing intestine that occupies about 3/5 the cross-sectional area of the nematode. Third-stage cuticle (cu3) has separated from second-stage cuticle (cu2). Intestinal lumen (IL) has moderate proliferation of microvilli in addition to broad units of cell extensions into lumen. Lipid droplets (LD) surrounded by numerous glycogen rosettes (GlR) occur throughout epithelium (IE). IEN, intestinal epithelial nucleus; H, hypodermis. Bar=1.0 µm.

Figure 207. Longitudinal section through genital primordium of Heterodera glycines J2, showing two large central germinal nuclei (gN) bordered terminally by two smaller somatic nuclei (N). Bar=1.0 µm.

 

Figure 208. Section through genital primordium of J2, showing part of somatic cell with characteristic crystalline bodies at high magnification. Compare with numerous crystalline arrays in fig. 207. Bar=1.0 µm.

 

Figure 209. Cross section of Heterodera glycines J3 at 5 days after inoculation, showing intestino-rectal valve with intercellular membranes, membrane junctions (MJ), and muscle elements (rm). Bar=1.0 µm.

 

Figure 210. Cross section posteriad to intestino-rectal valve of J3 at 5 hours after inoculation. Centrally located rectal lumen (rL) extends posteriad and ventrally to cuticularized anal opening shown in fig. 211. Bar=1.0 µm.

Figure 211. Longitudinal section of rectal and anal regions of infective Heterodera glycines J2. Lumen of intestine (IL) is shown anterior to intestino-rectal valve (Irv). Unlined membranes and membrane junctions constitute parts of intestino-rectal valve. Rectum (r) extends from posterior of intestino-rectal valve to cuticularized anal opening. Dorsal surface of rectum is attached to depressor ani muscles (ADM) that extend to dorsolateral sides of nematode body. an, anus; cu, cuticle; Sm, somatic muscle. Bar=1.0 µm.

Figure 212. Longitudinal section through tail region of Heterodera glycines J2, showing a dendritic process related to a phasmid. Slender neural rootlet (Nr) extends anteriad from phasmid site. Bar=1.0 µm.

Figure 213. Longitudinal section of Heterodera glycines J2, showing extreme posteriad region of body cavity in transition with amorphous fibrillar (f) region of tail terminus. Body cavity and fibrillar regions are enclosed by cuticle with characteristic epicuticle (Ep), exocuticle (Ex), flocculent electron-translucent intermediate zone (I), and striated endocuticle (En). Bar=1.0 µm.

 

Figure 214. Cross section through tail terminus showing fibrillar tail region enclosed by body cuticle with narrow noncontinuous zone of striated endocuticle (En), a wider flocculent intermediate zone (I), and an exocuticle (Ex) with indistinct boundary merging with I and bounded externally with well-defined electron-opaque epicuticle (Ep). Bar=1.0 µm.

 

Figure 215. Longitudinal and slightly tangential section of J2 tail, showing relatively homogeneous fibrillar (f) contents throughout tail region. Bar=1.0 µm.


Go to Chapter 10—Figure Captions

Back to Contents

Last Modified: 2/6/2002
Footer Content Back to Top of Page