Claeys, M.

Coomans, A.

Heyns, J.

Horizon / Pleins textes

Fundam. appl. NemalOl., 1992, 15 (4), 341-346.
Ultrastructure of the uterus of Xiphinema pinoides (Nematoda)
August COOMANS *, Myriam CLAEYS * and Juan HEYNS **
* Rijksuniversiteit Gent, lnstituut vaal' Dierkunde, K. L. Ledeganckstraat 35, 9000 Gent, Belgium and
** Department of Zoology, Rand Afrikaans University, P. O. Box 524, 2000 Johannesburg, South Africa.
Accepted for publication 7 August 1991.
Summary - A study of the ultrastructure of the uterus of Xiphinema pinoides showed that the basic features are similar to those
reported for X. mendianum and X. lheresiae. However, it differs in sorne details, and in the extreme rariry of crystalloids and absence
of spines. Apparently the glandular cells of the pars dilalala uleri produce large amounts of secretion which forms a thick layer
covering the inner plasma membrane of the cells bordering the lumen of the uterus. From this layer, membranous structures project
into the lumen that connect with globular inclusions of the Z-differentiation. The latter seem to be derived from the same secretion,
plus sorne engulfed material.
Résumé - Ultrastructure de l'utérus de Xiphinema pinoides {Nematoda} - L'etude de l'ultrastructure de l'uterus de
Xiphinema pinoides montre que sa structure de base est identique à celle precedemment rapportee pour X. meridianum et X.
lheresiae. Cependant, certains details sont différents, de même que l'extrême rareté des cristalloïdes et ['absence d'epines.
Apparemment, les cellules glandulaires de la pars dilalala Ulen produisent une quantite importante d'une secrétion formant une
couche epaisse recouvrant la membrane plasmatique interne des cellules bordant la lumiére de l'uterus. A partir de cette couche,
des structures membraneuses font saillie dans la lumiére, reliant ainsi sa couche interne aux inclusions globuleuses de la
différentiation Z. Ces derniéres paraissent constituees à partir de cette même secrétion et de materiel englobe.
Key-words : Xiphinema, u!trastructure, nemalOdes.
This paper is one of a series on the structure of the
female reproductive system in the genus Xiphinema.
The entire system has been investigated in X. pinoides)
but as ail other parts are completely comparable to those
in X. meridianum and X. lheresiae (Van de Velde el al.)
1990a) b), this study deals only with the uterus. The
terminology used follows Coomans (1965) and Van de
Velde el al. (1990a) b).
Materials and methods
Soil samples were collected in South Africa and
shipped to Ghent. In the laboratory, the nematodes were
extracted from the soil by the centrifugal-flotation
method, using a non-toxic silica gel (Ludox AS, Du Pont
de Nemours).
Adult females were picked out of the extraction
medium and placed in an ice bath for a few minutes in
order to stretch the specimens. Then they were killed
and fIXed in ice-cooled fIXative, composed of 0.75 %
acrolein, 1.5 % glutaraldehyde and 0.75 % paraformal-
dehyde in 0.1 M sodium cacodylate buffer. Mter ap-
proximately 15 h of fIXation at 7 "C, they were rinsed in
0.2 M sodium cacodylate buffer for 8 h. During this
rinse the nematodes were cut into pieces of roughly
200-300 llm, to facilitate penetration.
PostflXation took place in 2 % osmium tetroxide in
0.2 M sodium cacodylate buffer for 36 h and was
followed by an en bloc staining of 1 h in 2 % uranyl
acetate. The specimens were dehydrated in a graded
ethanol series and embedded in Spurr's resin.
Ultrathin sections were cut on a Reichert OMU-2
ultramicrotome and picked up on formvar-coated slot-
ted grids. The sections were post-stained in a LBK
ultrastainer) for 30 min in uranyl acetate at 40 "c and
5 min in lead stain at 20 "c.
Results
The uterus is comprised of a wide proximal part, the
pars dilacaca Uleri (p.d. u.) and a tubulaI' part that is
distally connected to the ovejector. Inside the tubulaI'
part, a short distance from the p.d.u. occurs the Z-
differentiation with four irregularly shaped inclusions
(Fig. 1).
The wall of the whole uterus consists of an outer basal
lamina, a muscle layer and an inner lining. A prominent
glandular epithelium occurs in the p.d. u.
The tubular part has a wide lumen and a relatively
thin wall (Fig. 2 A). The outer basal lamina (250-500 nm
thick) covers the outer plasma membrane of the muscle
cells (Fig. 2 B). The muscle filaments run predominantly
transverse and are arranged in bundles separated by thin
strands of cyroplasm. The filaments occupy a 1-2 llm
thick zone throughout most of the length of the tubular
part, but in the short (proximal) area between the p.d.u.
ISSN lJ64-5571/92/04/341 06 $ 2.60/ © Gauthier-Villars - ORSTOM 341
A. Coomans, M. Claeys & J. Heyns
\
i
., -t. p.
;
(~~?}.,\
" '\ i
\ i\ ,
\ 1
!.I
\~.
\\
; 1
"
O.j.- "
, ~
{ (
i. )
Fig. 1. Anrerior uterus of Xiphinema pinoides.
List of abbreviations : b.l. : basal lamina; cr. : crystalloid;
g.e.r. : granular endoplasmic reticulum; g.i. : globular inclu-
sion; i.l. : inner lining; m.l. : muscle layer; m.v. : microvilli; N:
nucleus of muscle cell; N' : nucleus of gland cell; n : nucleo-
lus; o.j. : ovejector; p. d. u. : pars dilatata uleri; s.e. : sperm cells;
s.V. : secretory vacuole; l.p. : tubular part of uterus; Z.d. :
Z-differentiation. (Bar = 60 .um.;
342
and the Z-differentiation (Fig. 2 C) the zone is 3-5 llm
thick. The nuclei of the muscle cells are quite promi-
nent, irregular in shape, with fineIy granular nucleo-
plasm, very electron-dense chromatin and a somewhat
less electron-dense nucleolus. The nuclei usually occur
near the outer cell membrane, buIge out of the uterus
contour, and are located peripheral ta the muscle fila-
ments (Fig. 2 A-C). Occasionally the nuclei may occur
inside the inward protrusions of the muscle cells where
they appear to lie between the muscle filaments and the
lumen wall (Fig. 2 A, lower nucleus). The inner cell
membrane is covered by a 250-500 nm thick, amorphous
substance, that together form the inner, folded lining of
the lumen. The folds are variable in shape and length,
they enclose cytoplasm and occasionally a nucleus (see
above). The lumen contains a fine granular material
within which are scattered sorne small electron-dense
globules and very few small crystalloids (Fig. 2 A).
The wall of the Z-differentiation has essentially the
same structure as that of the tubular part, but is slightly
thicker due to the greater number of muscle filaments
that occupy a 4-8 llm thick zone (Figs 2 C, 3 A). The
amorphous material on the inner plasma membrane
forms thin membrane-like extensions into the lumen
that sometimes encompass parts of the lumen (Figs 2 D,
3 B, C). Sorne of these projections enlarge, seem ta
engulf granular and other material from the uterine
lumen and connect with globular inclusions (Figs 3 B,
C). The latter consist of the same amorphous material
that forms the inner lining, and of vacuolar spaces with
different kinds of usually electron-dense material. These
vacuoles are formed when the amorphous material
encompasses material from the lumen; they vary con-
siderably in size and content, but crystalloids were not
observed in any of them (Figs 2 C, 3 A, C).
The pars dilalala uleri, which is about 50-70 Ilm long
and 15-18llm wide, is highly glandular throughout most
of its length, but compared ta the main part of the p.d. u.
the cells near the distal end are smaller. These gland ceIls
contain weil developed granular endoplasmic reticulum
and have abundant secretory material stared in a variery
of inclusions ranging from small granules ta huge
vacuoles (Figs 4 A, B). The secretory material, which is
moderately electron-dense, contains various inclusions
that are sometimes reminiscent of degenerated cell
organelles (Fig. 4 C). At the borderline of the large
vacuoles, the endoplasmic reticulum appears partly
broken up. The nuclei of the gland cells are larger and
less electron-dense than those of the muscle cells; the
nucleolus is generally bigger than that in the muscle cell
nuclei (Fig. 4 B). The gland cells occupy most of the
p.d. u. Towards the centre of the lumen, the apical
membranes of these cells may be higWy folded or give
rise ta long microvilli-like projections (Fig. 4 B). The
lumen becomes more evident distally where it connects
with the lumen of the tubular part. In between the gland
Fundam. appl. NemalOl.
UlLraslruClUre ojXiphinema pinoides
Fig. 2. A : SlightJy oblique transverse section through the tubular part of the uterus; B : Detail of the wall of the tubular part,
transverse section; C : Longirudinal section through the Z-differenriation; D : 1nner lining with membrane-like extensions
(arrowheads) near Z-differenriation, transverse section. (Bar equivalenl : A = 2 p.m; B = 1 ,um; C = 2 p.m; D = 1 pm.) For
abbreviations, see Fig. 1.
Vol. 15, nO 4 - 1992 343
A. Gaamans, M. Glaeys & J. Heyns
Fig. 3. A : Transverse section through Z-differentiation. B-C : Details of connections between inner lining, membrane-like
extensions (arrowheads) and globular inclusions in the Z-differentiation, transverse section. (Bar equivalenl "A = 2 .um; B = l.um;
G = 1 .um,) For abbreviations, see Fig. 1.
344 Fundam. appl. NemalOl.
U/lraslruClure ojXiphinema pinoides
Fig. 4. A : Longitudinal section of the glandular part of the pars di/alQlQ uleri; B : Transverse section of the same; C : Details
of the eytoplasm and inclusions of a gland cell. (Bar equivalenl .' A = 4 ,um; B = 2 j1m; C = 0.5 j1m.) For abbreviations, see Fig. 1.
Vol. 15, nO 4 - 1992 345
A. Coomans, M. Claeys & J. Heyns
cells, and more so distally than proximally, sperm cells
are usually stored in clusters of five to about twenty
(Fig. 4 A).
At the base of the glandular epithelium the inner cell
membrane of the muscle cells forms narrow infolds
filled with cyroplasm and sporadically wider folds enclos-
ing nuclei. However, most of the muscle cell nuclei are
inside the main part of the wall, i.e. below the glandular
epithelium, centrally from the muscle filaments. The
latter are mainiy transverse, but also oblique in orien-
tation and form a 0.65-1.3 llm thick layer. The outer
basal lamina is 250-500 nm thick; it forms many
short (1-2 llm) outward protrusions (Fig. 4 A).
Discussion
The structure of the uterus in X pinoides resembles
that described for X meridianum (Van de Velde el al.,
1990a) and X lheresiae (Van de Velde el al., 1990b)
except in sorne details, such as the extreme rarity of
crystalloids and the absence of spines.
Large and active glandular cells in the p.d. u. appar-
ently produce large amounts of a secretion which, once
in the uterine lumen, covers the entire inner plasma
membrane of the bordering cells to form a thick inner
lining of the lumen. The same secretion also seems to
form the globular inclusions of me Z-differentiation
since - apart from the" engulfed " material - these
inclusions have the same electron density and are in
direct contact wim the lining. Why the globular inclu-
sions form in the Z-differentiation area and not else-
where is not known. However, the membrane-like pro-
jections from the inner lining in that area may " catch"
or act as accretion centres for sorne of the secretion that
enters the uterine lumen. The globular inclusions could
then form around such centres by further deposition of
secretion, thereby also engulfing other substances pre-
sent in the lumen. This would explain me differences in
electron-density and configuration of these inclusions.
The amorphous secretion on the inner plasma mem-
brane of the muscle cells presumably protects these cells
from damage during egg passage. Such a function does
not exclude the previously proposed hypothesis that the
secretion contributes to the formation of an outer layer
of me egg shell (Coomans, 1965; Bird, 1976; McClure
& Bird, 1976; Bleve-Zacheo el al., 1976), but is comp-
lementary to it. In a number of species the secretions
346
also form the globular or variously shaped inclusions,
called the Z-differentiation. We are still unable to offer
any proof of their function. Siowing down the egg pas-
sage may be a result of their presence, but is not neces-
sarily a primary function. The globules may be simply
by-products of the secretory activity of the p. d. u. The
same could be true for the crystalloids found in a num-
ber of species.
The secretion process in the gland cells of the p.d. u.
is to sorne extent enigmatic. Among gland cells there
have been clear signs of organelle degeneration includ-
ing fragmentation of endoplasmic reticulum at the
margin of or inside the large secretion-filled vacuoles.
Almough the possibility of artifacts cannot be excluded,
me constant presence of these phenomena in ail five
specimens studied with TEM points to the occurrence
of an apparently autophagous mechanism and a possible
apocrine (cf. also Van de Velde el al., 1990a) or even
holocrine type of secretion.
Acknowledgments
This research was supported by the Belgian Fund for
Collective Fundamental Research, grant 2.0003.86.
References
BlRo, A. F. (1976). The development and organization of
skeletal structures in nematodes. In : Croll, N. A. (Ed.). The
Organizalion of NemalOdes, London & New York, Acade-
mie Press: 107-137.
BLE\'E-ZACHEO, T., CASTELLi\:"O, M. A. & L.AMBERTI, F.
(1976). Preliminary studies on the ultrastructure of the
female gonad of Xiphinema index and X. medilerraneum
(Nematoda : Longidoridae). NemaLOI. medil., 4 : 41-55.
COOMANS, A. (1965). Structure of the female gonads in
members of the Dorylaimina. NemaLOlogica, 10 : 601-622.
MCCLURE, M. A. & BIRD, A. F. (1976). The rylenchid (Nema-
toda) egg shell : formation of the egg shell in Meloidogyne
javanica. ParasiLOlogy, 72 : 19-28.
Vc\':'-! DE Vu. DE, M. c., COO,\\Al'S, A., HEYNS, ]. & CU\EYS, M.
(1990a). Ultrastructure of the female reproductive system
of Xiphinema meridianum (Nematoda). Revue NémaLOI.,
13: 211-223.
VAN DE VELDE, M. c., COOMANS, A., HEYNS,]. & CLAEYS, M.
& HUTSEBAUT, M. (1990b). Ultrastructure of the female
gonoduct of Xiphinema lheresiae (Nematoda). Revue Néma-
101., 13 : 449-461.
Fundam. appl. NemaLOI.


Ultrastructure of the uterus of Xiphinema pinoides (Nematoda)

Abstract

Similar works

Full text

Available Versions

Horizon / Pleins textes