Chapter 5Ultrastructure of Esophageal Gland Secretory
Granules in Juveniles of the Soybean Cyst Nematode, Heterodera
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.
section through lip region. Tangential section through stylet
) shows attached feeding tube (FT
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;
, stylet orifice. Bar=1.0 µm.
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.
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.
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
) lies within ampulla cytoplasm close to esophageal
). Bar=1.0 µm.
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.
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
section through procorpus-metacorporeal sphincter muscle (Spm
valve, showing tightly packed microtubules (Mt
control movement of secretion granules (SG
) but allow
cytoplasmic continuity within dorsal gland extension. EL
esophageal lumen; m
, metacorpus; prc
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.
Cross section through sphincterlike muscle (Spm
region at base of metacorpus. Dx
, dorsal gland extension;
, subventral gland extension. Bar=1.0 µm.
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.
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.
Go to Chapter 6Figure Captions
Back to Contents