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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 3—Ultrastructure of Anterior Neurosensory Organs of Juveniles of the Soybean Cyst Nematode, Heterodera glycines

Figure Captions

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.

Figure 44. Frontal section through two inner labial receptor canals (ILC) opening into prestoma. Right sector shows cilia (ILci, Aci) within inner labial (ILC) and amphidial receptor canals (AC). Electron-opaque intermembrane accumulations vary among outer (OAci) and inner accessory receptor cilia (IAci). CF, cephalic framework; St, stylet; SW, 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 µm.

 

Figure 48. Frontal section through inner labial (ILC), outer labial (OLC), and cephalic (CRC) receptor canals. cu, cuticle; IAci, inner accessory receptor cilia; OAci, outer 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 µm.

 

Figure 50. Section 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, CRci). Amphidial canals (AC) are bounded centripetally by inner accessory receptor cilia (IAci) and dorsoventrally by outer accessory receptor cilia (OAci). Electron-opaque membranous materials (EOMM) 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 materials (EOM) fill channel openings that appear to be formed by hypodermis. LS, lumen of stylet; St, stylet; SW, 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.

 

Figure 52. Cross section through anterior sensilla below cephalic framework, showing dendrite-related laminar membrane (LM) and vesicular membrane (VM). Bar=0.5 µm.

 

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 µm.

 

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 (CR–1, CR–2, CR–3, CR–4) having up to eight doublets and four singlet microtubules per cilium. Sections of outer labial receptors OLR–1 and OLR–2 were made through basal region of cilia, while receptors OLR–3 and OLR–4 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.

 

Figure 57. Longitudinal 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) accessory receptors. Bar=1.0 µm.

 

Figure 58. Longitudinal section through basal portion of several outer accessory cilia corresponding to area shown in figs. 59–61. 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. Bar=1.0 µm.

 

Figure 59. Section 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 µm.

 

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. Bar=1.0 µm.

 

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. Bar=0.25 µm.

 

Figure 62. Cross section through vertical projection of nerve process dendrite (NPD) where it is attached by membrane junctions (arrows) to other dendrites of lateral nerve bundle (LNB). Microvillar 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.

 

Figure 65. Longitudinal 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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Last Modified: 2/6/2002