Chapter 3Ultrastructure of Anterior Neurosensory Organs
of Juveniles of the Soybean Cyst Nematode, Heterodera glycines
Figure 43. Composite
median dorsoventral view of stylet region of soybean cyst nematode,
Heterodera glycines J2. Three of seven amphidial cilia
are shown. Dendrite forming the microvillar nerve process is ventral
to the nerve bundle (note fig. 62)
that gives rise to amphidial and accessory cilia. Cephalic framework
includes the base shown here and the hexaradiate cuticular structures
anterior to it.
section through two inner labial receptor canals (ILC
opening into prestoma. Right sector shows cilia (ILci
) within inner labial (ILC
) and amphidial receptor
). Electron-opaque intermembrane accumulations
vary among outer (OAci
) and inner accessory receptor cilia
, cephalic framework; St
, stomatal wall. Bar=1.0 µm.
Figure 45. Illustration
of an inner labial receptor cilium (ILci) with an electron-opaque
central core (EOC). Bar=0.1 µm.
Figure 46. Cross section
through cephalic framework (CF) showing canals of inner
labial receptors (ILC), outer labial receptors (OLC),
cephalic receptors (CRC), and amphid (AC). Canals
enclose secretion products and, in some cases, sections of ciliary
extensions. EOM, electron-opaque material; IAci,
inner accessory receptor cilium; St, stylet; SW,
stomatal wall. Bar=1.0 µm.
Figure 47. Cross section
of a dense core region of an inner labial receptor cilium. Bar=0.1
section through inner labial (ILC
), outer labial (OLC
and cephalic (CRC
) receptor canals. cu
, inner accessory receptor cilia; OAci
accessory receptor cilia; SW
, stomatal wall. Bar=1.0 µm.
Figure 49. Transverse section
through base of cephalic framework. Portions of an inner accessory
receptor cilium (IAci) extend from initial lateral position
to a subventral cephalic sector. Section also shows transverse
orientation of several outer accessory receptor cilia (OAci)
extending from a peripheral lateral position to adjacent subventral
and subdorsal cephalic sectors. AC, amphidial canal. Bar=1.0
through base of cephalic framework (CF
) showing paired
cilia in each of six inner labial receptor canals (ILC
Each of the outer labial (OLC
) and cephalic (CRC
receptor canals contains a single cilium (OLci
Amphidial canals (AC
) are bounded centripetally by inner
accessory receptor cilia (IAci
) and dorsoventrally by outer
accessory receptor cilia (OAci
). Electron-opaque membranous
) in dorsal and ventral segments of cephalic
framework are regions where somatic and stylet protractor muscles
attach to cephalic framework. Irregular masses of electron-opaque
) fill channel openings that appear to be
formed by hypodermis. LS
, lumen of stylet; St
, stomatal wall. Bar=0.5 µm.
Figure 51. Section through
an inner labial receptor canal (ILC) showing enclosed cilia
(ILci) and electron-opaque materials (EOM) that
surround the cilia. Mt, microtubules. Bar=0.1 µm.
through anterior sensilla below cephalic framework, showing dendrite-related
laminar membrane (LM
) and vesicular membrane (VM
Figure 53. Longitudinal
section through a sensillum showing convoluted (cvM) and
related laminar membranes (LM) surrounding basal region
of receptor. Membranes evaginate into a support cell. Bar=0.5
Figure 54. Cross section
through basal regions of an inner labial receptor, showing doublets
and singlets of microtubules within paired cilia. Bar=0.5 µm.
Figure 55. Section of cilia
slightly posteriad to sector in fig. 54, showing a receptor with
irregular membrane outline. Doublets and singlets of microtubules
of both cilia eventually form basal bodies, which in turn are
supported by nerve cell bodies. Bar=0.5 µm.
Figure 56. Cephalic receptors
(CR1, CR2, CR3, CR4)
having up to eight doublets and four singlet microtubules per
cilium. Sections of outer labial receptors OLR1 and
OLR2 were made through basal region of cilia, while
receptors OLR3 and OLR4 were sectioned
anteriad. Inner accessory receptor cilia (IAci) appear
circular in outline and lack membrane complexes of electron-opaque
deposits that characterize outer accessory receptor cilia. Large
number of outer accessory receptor cilia (OAci) in anterior
region is attributed to branching of those cilia present in basal
region. Sheath cells of various receptor cilia are bordered by
dense network of microtubules (MtH) that extend from hypodermal
layer between cuticle and somatic musculature to these receptor
sites. Hypodermis bordered by these microtubules forms irregular
channels (IC) that may have electron-opaque materials (EOM),
especially in anterior regions of cephalic framework. AC,
amphidial canal; ILR, inner labial receptor. Bar=1.0 um.
frontal section through anterior region. Anteriad to branched
cilium is a lateral sector of cephalic framework showing ciliary
terminals of inner (IAci
) and outer (OAci
receptors. Bar=1.0 µm.
Figure 58. Longitudinal
section through basal portion of several outer accessory cilia
corresponding to area shown in figs. 5961. Micrograph shows
doublet microtubules (MtD) within cilia and their continuity
with rootletlike (R) formations of dendrite terminals that
contain numerous singlet microtubules (MtS) and mitochondria
(Mc). One of the dendrites projects two cilia. Membrane
junction (MJ) between dendrites restricts accumulation
of electron-opaque materials (EOM) anteriad to junction.
through basal region of cilia that enter amphidial canal and constitute
the outer accessory receptors (OAci
). Electron-opaque material
is dispersed throughout interciliary spaces at a level where microtubule
doublets and singlets have a symmetrical arrangement. Bar=1.0
Figure 60. Transverse section
through cilia and supporting dendrites within basal region of
an amphid, showing diverse arrangement of microtubule doublets
(MtD), ciliary rootlets (R), membrane junctions
(MJ) between cilia, and a sheath cell. Tubular (to)
or microvillar outgrowths are part of nerve process dendrite.
Figure 61. High magnification
of a portion of basal region of amphidial canal and outer accessory
cilia. Four cilia show clearly defined peripheral doublets of
microtubules in each cilium. Eight evenly spaced doublets of microtubules
are attached to a fibrillar ring (fr) centripetally. Each
doublet also has a fibrillar strand that extends from apposed
boundaries of their membranes to cilium membrane. Strand from
each doublet traverses the axoplasm to form bifid attachments
to membrane of each cilium. Four singlets that occur within central
ring are attached to ring opposite alternate microtubule doublets.
through vertical projection of nerve process dendrite (NPD
where it is attached by membrane junctions (arrows
other dendrites of lateral nerve bundle (LNB
tubular outgrowths (to
) of dendrites are shown in terminal
region of nerve process dendrite. Bar=1.0 µm.
Figure 63. Nerve process
dendrite (NPD) with ventral and posterior orientation within
amphidial sheath cell (ASC) and completely surrounded by
microvillar and tubular outgrowths or membrane extensions. These
tubular outgrowths (to) occur either singly or in groups
as they contact the unit membrane of the amphidial sheath cell.
Electron-opaque material between tubular outgrowths and supporting
cell is part of intermembranous accumulation that occurs through
nerve process. Some terminal accumulations appear in electron-opaque
vesicles (EOV) or elongated sacs. Bar=1.0 µm.
Figure 64. Pair of cilia
(arrows) projects from nerve process dendrite. Cross sections
of comparable cilia show that each cilium has a set of eight peripheral
doublets of microtubules in basal region. Bar=1.0 µm.
section of a microvillar nerve process with paired cilia (NPci
Electron-opaque materials (EOM
) are retained in elongate
membranelike sacs (s
) and vesicles (EOV
). Some electron-opaque
vesicles appear to distend into larger vesicles with granular
contents. Bar=1.0 µm.
Figure 66. Rootlet (R)
supporting the microvillar nerve process of paired cilia of fig.
65. Bar=0.5 µm.
Figure 67. Terminals of
some microvilli of nerve process of fig. 65. EOV, electron-opaque
vesicles. Bar=0.5 µm.
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