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STICHOSOME ULTRASTRUCTURE OF THE FISH NEMATODE CAPILLARIA PTEROPHYLLI
HEINZE, 1 9 3 3
ZD'ÁRSKÁ Z*. & NEBESÁROVÁ J . *
Summary:
Résumé
The stichosome (posterior glandular esophagus) of Capillaria
pterophylli Heinze, 1933 consists of large gland cells (stichocytes|
and lumenal epithelium with cuticular lining. Both structures are
enclosed in a reticulum of muscle cells. The stichocyte cytoplasm
contains small cisternae of rough endoplasmic reticulum, Golgi
complexes, one kind of electron dense secretory granules,
mitochondria and a branching system of intracellular collecting
ducts without filament bundles around them.
PTEROPHYLLI HEINZE, 1933, PARASITE DE POISSON
KEY WORDS : Nematoda, Capillaria pterophylli, ultrastructure,
stichosome.
: ULTRASTRUCTURE DU STICHOSOME DE CAPILLARIA
te stichosome (partie postérieure glandulaire de l'œsophage) de
Capillaria pterophylli Heinze, 1933 est formé de grandes cellules
glandulaires (stichocytes) et d'un épithélium revêtu de cuticule
entourant la lumière œsophagienne. Ces deux structures sont
enfermées dans un réseau de cellules musculaires. Le cytoplasme
du stichocyte contient des petites citernes de reticulum
endoplasmique rugueux, des complexes de Golgi, un seul type de
granules de sécrétion denses aux électrons, des mitochondries et
un système ramifié de canaux collecteurs intracellulaires qui ne
sont pas entourés de faisceaux de filaments.
MOTS CLÉS : Nematoda, Capillaria pterophylli, ultrastructure, stichosome.
T
h e present paper, describing the ultrastructure
o f t h e s t i c h o s o m e o f Capillaria
pterophylli
Heinze, 1 9 3 3 , c o m p l e t e s o u r studies o n the
ultrastructure o f this nematode (Zd'arska & Nebesáfová
1999. 2 0 0 0 ) . T h e e s o p h a g u s o f the superfamily Trichinelloiclea
Ward, 1907 ( 1 8 7 9 ) consists o f t w o distinct
parts, the anterior muscular part and posterior glandular
part termed the s t i c h o s o m e . T h e s t i c h o s o m e is an
e x o c r i n e organ. T h e main c o m p o n e n t o f the stichos o m e are large glandular cells, the stichocytes. Stic h o s o m e ultrastructure has b e e n studied earlier in the
family Trichuridae b y Sheffield ( 1 9 6 3 ) in
Trichuris
muris ( O w e n , 1 8 3 5 ) a n d T. vulpis Froelich, 1789, and
b y Wright ( 1 9 7 2 ) in Trichuris
myocastoris
Enigk and
T. vulpis Froelich, 1789; in the family Trichinellidae b y
Bruce (1970), Despommier (1974), Despommier &
Müller ( 1 9 7 6 ) and Takahashi et al. ( 1 9 9 2 ) in
Trichinella
spiralis (Schrank, 1 7 8 8 ) ; in t h e family Capillaridae b y
Wright ( 1 9 7 2 ) in Capillaria
hepatica
Bancroft, 1 8 9 3 ,
1933 a n d by McDarby et al. ( 1 9 8 7 ) in Capillaria
catostomi (Pearse, 1 9 2 4 ) . From the family Cystoopsidae
only histological date are available o f t w o species o f
Dioctowittus
Chabaud & Le Van Hoa, 1 9 6 0 (Bain &
Ghadirian ( 1 9 6 7 ) ) .
* Institute of Parasitology, Academy of Sciences of the Czech Republic. Branisovská 31, 37005 Ceské Budejovice, Czech Republic.
Correspondence: Z. Zd'árská, DSC.
Tel.: +42-38-7775437 - Fax: +42-38-5300388.
E-mail: [email protected]
In the recently accepted c o n c e p t i o n o f Moravec (1982,
1 9 8 7 ) o f a n e w systematic arrangement o f nematodes
o f t h e family Capillariidae, Capillaria
hepatica
(Bancroft, 1 8 9 3 ) d o e s not b e l o n g to the genus
Capillaria
s.s., but to the g e n u s Calodium
Dujardin, 1 8 4 5 , a n d
Capillaria catostomi (Pearse, 1924) to the genus Pseudocapillaria
Freitas, 1 9 5 9 . Therefore, in the n e w systematic arrangement, our study represents the first description o f the stichosome ultrastructure in the genus
Capillaria
s.s.
MATERIALS AND METHODS
F
e m a l e a n d male s p e c i m e n s o f C. pterophylli
Heinze, 1 9 3 3 collected from the intestine o f an
angel fish Pterophyllum
scalare
(Lichtenstein,
1823) w e r e rinsed in saline, fixed in 3 % glutaraldehyde in 0.1 M phosphate buffer (pH 7 . 2 ) at 4 ° C for
two hours, postfixed in 1 % O s O ai 4° C for two hours,
dehydrated in an ethanol series a n d e m b e d d e d in
Durcupan via a c e t o n e . A series o f ultrathin sections o f
the w h o l e stichosome (from the first stichocyte to the
last o n e encircled b y t w o p s e u d o c o e l o m o c y t e s ) w e r e
cut using a Reichert J u n g Ultracut E ultramicrotome,
double-stained with uranyl acetate a n d lead citrate
and v i e w e d in a transmission electron m i c r o s c o p e
J E O L 1010 operated ai 8 0 kV. Semi-thin sections were
stained in toluidine blue.
4
181
Figs 1-4. - Stichocyte of C. pterophyili. Fig. 1. Oblique TEM section through the body of C. pterophylli in the region of the stichosome.
The stichosome fills the entire pseudocoelom. The stichocyte (ST) surrounds the lumen (L) of the esophagus. NU: nucleus, N: nucleolus,
S: dense secretory granules, D: collecting ducts, BB: bacillary band gland cells, arrow: pore of BB, C: cuticle, scale bar = 5 µm. Fig. 2. Detail
of Fig. 1. NU: nucleus, N: nucleolus, S: secretory granules, D: collecting ducts, CI: small cisternae of rough endoplamic reticulum, scale
bar = 1 µm. Fig. 3. Detail of Fig. 2 (bottom right). Collecting ducts (D) contain electron dense secretory material (arrows). S: secretory granules, scale bar = 200 nm. Fig. 4. Lumen of the esophagus lined by a thin cuticle (arrows) connected with a thin epithelial layer. D: collecting ducts, S: secretory granules, scale bar = 1 µm.
182
RESULTS
T
he s t i c h o s o m e o f C. pteropbylli
consists o f a
single row o f large gland cells, the stichocytes
(Fig. 1) and an e s o p h a g u s with cuticular lining
(Figs 1, 4). T h e w h o l e surface of the stichocytes adheres
to a thin basal lamina. O v e r this basal lamina the stic h o s o m e surface through the w h o l e length covers a
meshwork (fenestrated layer) of muscle cells (Figs 5, 6 ) .
T h e dimensions of the lobes on the surface of the stic h o c y t e (Fig. 1) d e p e n d on the contraction or dilatation o f the peristichocytal muscle bands. T h e muscle
cells, localized external to the stichocyte basal lamina
contain myofilaments (Fig. 5) and are c o n n e c t e d with
the basal lamina b y h e m i d e s m o s o m e s (Fig. 6 ) .
Concentration of electron dense granules occur around
the nucleus and collecting ducts (Figs 1, 2, 3, 4 ) .
T h e r e is a great size diversity in granules (Figs 2, 3).
Smaller-sized granules could represent stages of granulogenesis. Mature granules measure 500 nm. S o m e
o f them are round, other o f irregular shape. T h e stic h o c y t e cytoplasm contains a high concentration o f
rough endoplasmic reticulum with abundant small cistemae (Fig. 2 ) , Golgi systems, and mitochondria mainly
concentrated at the periphery o f the cell. Around the
nucleus, a m o n g the dense secretory granules, there are
aggregations o f narrow collecting ducts containing
small amount of electron dense material (Fig. 3 ) . T h e s e
collecting ducts, o f irregular contour, pass through the
cell to the e s o p h a g u s (Figs 1, 4 ) .
T h e e s o p h a g u s (Fig. 4 ) comprises the cuticle and flattened epithelial cells c o n n e c t e d by means o f very fine
d e s m o s o m e s . No myofilaments were identified in this
part o f esophagus. T h e epithelial cells are separated
from the stichocyte p l a s m a l e m m a by a thin basal
lamina. At s o m e parts these epithelial cells are not
detectable, mainly at the level o f the last stichocyte,
w h e r e small cytoplasmic evaginations of the stichocyte
are c o n n e c t e d directly to the cuticle by dense material. At the level o f the last stichocyte, the stichosome
is c o n n e c t e d with the basal lamina of two pseudoc o e l o m o c y t e s . At this level the esophagus, bordered
by a cuticle, terminates, and continues as the intestinal
lumen bordered by a microvillous z o n e o f the entero¬
cytes ( s e e Zd'árská & N e b e s á r o v á 1999 - Figs 1, 2, 3 ) .
DISCUSSION
I
n cross sections o f C. pteropbylli
o n e unicellular stichocyte surrounds the e s o p h a g u s as in
Calodium
hepaticum
(Wright, 1972), Pseudocapillaria
cato-
Figs 5-6. - Stichocyte of C. pteropbylli. Fig. 5. Muscle cells (ME) on the stichocyte surface. Arrows: basal lamina on the stichocyte surface,
S: secretory granule, PC: pseudocoelom, scale bar = 200 nm. Fig. 6. Contracted part of the muscle cell (ME) with cross sectioned myofilaments and hemidesmosome (arrow), attaching this part to the stichocyte basal lamina (BL). PC: pseudocoelom, scale bar = 200 nm.
183
stomi (Mc Darby et al,
1 9 8 7 ) , Trichuris
s p e c i e s (Shef-
field, 1963; Jenkins, 1970; Wright, 1972) and
Trichinella
(Khan, 1966; B r u c e , 1970; D e s p o m m i e r , 1974;
spiralis
D e s p o m m i e r & Müller, 1976; Takahashi et al,
1 9 9 2 ) . T h e unicellular stichocytes o f C.
1990,
pterophylli,
and the a b o v e m e n t i o n e d s p e c i e s , differ from
voluminous syncytial stichocytes o f the g e n u s
wittus
the
T h e well d e v e l o p e d peristichocytal m u s c l e reticulum
hepaticum
and Trichuris
Trichinella
spiralis
as in
Calodium
species (Wright, 1 9 7 2 ) and
( B r u c e , 1970; D e s p o m m i e r , 1974;
Takahashi et al., 1 9 9 0 ) is important for the contractions
that can b e transmitted through the s t i c h o s o m e to the
e s o p h a g u s and from the e s o p h a g u s to the intestine.
Their function is probably to s q u e e z e the content o f
the s t i c h o s o m e part o f the e s o p h a g u s to the intestine.
T h e s t i c h o s o m e part o f the e s o p h a g u s in C.
undoubtedly
C. hepaticum,
C. pterophylli
o c c u r in
T. spiralis
C. pterophylli
and Dioctowittus
as in Trichuris
as in
s p p . In
spp, they have not yet
b e e n s e e n in electron microscopy b e c a u s e o f the great
sampling p r o b l e m involved in locating this single,
small structure in the large stichocytes.
Diocto-
( B a i n & Ghadirian, 1967; Moravec 2 0 0 1 ) .
o f the s t i c h o s o m e in C. pterophylli,
lumen
pterophylli
ACKNOWLEDGEMENTS
W
e are grateful for the help given by Dr F. Moravec and Ing. B . Skoríková in collecting the
parasitized hosts. W e
also appreciate
the
technical assistance o f Mr. A. Polák and Mrs. P. Masarová.
This study was supported b y a grant from the Grant
Agency o f the Czech Republic n o . 524/97/0009 and a
grant o f the A c a d e m y o f S c i e n c e s o f the Czech R e p u blic n o . K2-022-601.
c o m p r i s e s the cuticle and thin layer o f epithelial cells
c o n n e c t e d with the stichocyte basal lamina. As in
C. hepaticum
(Wright, 1 9 7 2 ) n o myofilaments are pre-
sent in the s t i c h o s o m e part o f the e s o p h a g u s o f C. pteIntracellular filament bundles localized around the collecting ducts in C. hepaticum
(Wright, 1 9 7 2 ) w e r e not
d e t e c t e d in the stichocytes o f C. pterophylli.
Electron-
dense secretory granules observed in stichocytes o f the
anterior, middle and posterior part o f the stichosome,
w h i c h are c o n c e n t r a t e d around the stichocyte c o l l e c ting ducts, probably desintegrate w h e n entering into
the ducts. In the collecting ducts o f C. pterophylli
some
electron d e n s e material is present and presumably is
carried from the stichocyte into the esophagus. No granules w e r e o b s e r v e d in the canalicular tree. W e d o not
divide the mature e l e c t r o n - d e n s e granules in C.
ptero-
into two types. In our opinion c o e x i s t e n c e o f
two types o f granules (more or less rounded) in C. pterophylli
represents two stages o f granulogenesis which
can results, as d o c u m e n t e d in T. spiralis
(Takahashi,
1 9 9 2 ) , in a difference in antigenicity. T h e d e n s e secretory granules probably contain s o m e o f the e n z y m e s
identified in
Trichuris
muris
b y Nimmo-Smyth
Keeling ( 1 9 6 0 ) . In transportation o f the
and
stichocyte
secretory product from the collecting ducts to the e s o phagus lumen assist probably contractions o f the peristichocytal m u s c l e reticulum.
C. pterophylli
has not confirmed a pore-like o p e n i n g
o f the stichocytes to the e s o p h a g u s as reported b y
B r u c e ( 1 9 7 0 ) and Takahashi et al. ( 1 9 9 2 ) in
spiralis,
Wright ( 1 9 7 2 ) in Calodium
Bain & Ghadirian ( 1 9 6 7 ) in Dioctowittus
D. wittei.
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BIRD
Structure of esophagus of the infective juvenile
and adult Trichinella spiralis. Journal of Parasitology, 1970,
56, 540-549.
BRUCE R.G.
D.D. The stichocyte of Trichinella spiralis during
morphogenesis in the small intestine of the rat. In: Trichinellosis. Kim C. (ed.) Intext Educational Publishers,
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D . D . & MÜLLER M . M . The stichosome and its
secretion granules in the mature muscle larva of Trichinella spiralis. Journal of Parasitology,
1976, 62, 775-785.
DESPOMMIER
MCDARBY M.B.,
WILHEM W . E . ,
LAMOREAUX W . J .
& COONS
L.B.
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Z.A. The postembryonic development of Trichinella spiralis with special reference to ecdysis. Journal of Parasitology, 1966, 52, 248-259.
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Our ultrastructural investigation o f the s t i c h o s o m e o f
Trichinella
hepaticum,
and
chabaudi
and
At the ultrastructural level in Trichuris
spe-
cies Sheffield ( 1 9 6 3 ) , J e n k i n s ( 1 9 7 0 ) and Wright ( 1 9 7 2 )
w e r e u n a b l e to detect these pore-like o p e n i n g s too.
Pore-like o p e n i n g s o f stichocytes to the e s o p h a g e a l
184
E. Description d'une nouvelle espèce
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ZDÁRSKÁ Z. & NEBESÁROVÁ
Reçu le 10 février 2001
Accepté le 6 décembre 2001
185