Eisenback, J.D.

Gnanapragasam, N.C.

Horizon / Pleins textes

Fundam. appl. NemalOl., 1992, IS (4),347-353.
Additional notes on the morphology of Meloidogyne brevicauda
Jonathan D. EISENBACK * and Nalini GNANAPRAGRASAM **
* Department of Plant Pathology, Physiology, and Weed Science,
Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA, and
** Nematology Division, Tea Research lnstitute, St. Coombs, Talawakale, S1'i Lanka.
Accepted for publication 9 August 1991.
Summary - Females, males, and second-stage ;uveniles of Meloidogyne brevicauda Loos, 1953 were examined by light and
scanning electron microscopy. The labial disc of females and males is distincùy separated from the lips by a deep groove. In the
second-stage juvenile, the labial disc and lips are divided by a groove but are joined by a small band of cuticle. Head annulations
are absent in ail three life stages and the lips extend posteriorly to the first body annule. The tail of the male is marked by a
crescent-shaped fold around the posterior ponion of the cuticle surrounding the cloacal opening. The tail of the second-stage
juvenile is marked by transverse grooves that radiate from the posterior end of the lateral field. Also, the phasmids open on the ventral
edge, rather than in the middle of the lateral field. The morphology of M. brevicauda is quite different from the four most common
species and most others examined closely, but is similar in many respects to that of M. coffeicola Lordello & Zamith, 1960, M. indica
Whitehead, 1968, M. propora Spaull, 1977, and M. nalaliei Golden, Rose & Bird, 1981.
Résumé - Notes supplémentaires sur la morphologie de Meloidogyne brevicauda - Des femelles, des mâles et des
juvéniles de deuxième stade de Meloidogyne brevicauda Loos, 1953 ont été examinés en microscopies optique et électronique à
balayage. Le disque labial des femel1es et des mâles est distinctement séparé des lèvres par une rainure profonde. Chez les juvéniles
de deuxième stade 02), le disque labial et les lèvres sont également séparés par une rainure, mais demeurent reliés entre eux par
une petite bande de cuticule. L'annélation de la tête est absente chez les adultes et les J2, et les lèvres s'étendent postérieurement
au premier anneau du corps. La queue du mâle se distingue par un repli en forme de croissant soulignant la panie postérieure de
la cuticule entourant l'ouvenure cloacale. La queue des J2 se distingue par des rainures transversales qui divergent à panir de
l'extrémité postérieure du champ latéral. Les phasmides s'ouvrent ainsi sur le côté ventral plutôt qu'au milieu du champ latéral.
La morphologie de M. brevicauda est assez différente de celle des quatre espèces les plus communes et de celle de la plupan des
autres espèces examinées en détail, mais elle est semblable, par plusieurs aspects, à celle observée chez M. coffeicola Lordello &
Zamith, 1960, M. indica Whitehead, 1968, M. propora Spaull, 1977, et M. nataliei Golden, Rose & Bird, 1981.
Key-words : Meloidogyne, morphology, nematodes.
Meloidogyne brevicauda Loos, 1953 was described
nearly 40 years aga as a root-knot species parasitizing
mature tea in Sri Lanka (Loos, 1953). It was the first
description of a new species of root-knot nematode after
Chitwood (1949) described or delineated five species and
placed them into the genus Meloidogyne Goeldi,1887.
Since 1953, M. brevicauda has been reported only in Sri
Lanka and India (Rao, 1970; Silvapalan, 1972, 1978;
Lamberti et al., 1987). Very few additional morphologi-
cal studies have been completed since it was described
(Whitehead, 1968). The purpose of this paper was to
reexamine the morphology of M. brevicauda. Sorne of
the morphological details that were in the original
description were quite different from that described for
most root-knot nematodes. We wanted to confirm and
clarify these morphological characters using light and
scanning electron microscopy. Our hope was to deline-
ate new characters that may help reveal the phylogenetic
relationships of M. brevicauda with other species within
the genus and subfamily. We have previously reported
results from preliminary investigations (Eisenback &
Gnanapragrasam, 1986).
Materials and methods
Specimens of Meloidogyne brevicauda were recovered
from infected roots of tea collected from a plantation
located 80 km from the Tea Research Institute of Sri
Lanka, at an altitude of 1050 m, where the climate is
much cooler than that of the Tea Research Institute.
Second-stage juveniles, males, and females were pre-
pared for light and scanning electron microscopy (SEM)
as previously described (Eisenback & Hirschmann,
1979; Eisenback el al., 1980). At least 30 specimens of
each life stage were examined.
Results
FE MALES
The anterior end of the female (Fig. 1 A) contains the
esophagus which includes a narrow procorpus, a large
lSSN 1164-5571/92/04/347 07 $ 2.70/ © Gauthier-Villars - ORSTOM 347
J. D. Eisenback & N. Gnanapragrasam
B
D
c
Fig. 1. Meloidogyne brevicauda Loos, 1953. A: Female head including esophagus; B : Surface morphology of juvenile tail; C-E :
Optical section of medial plane of juvenile tail.
metacorpus, a narrow isthmus, and a large glandular
region that has one dorsal and two subventral esophageal
gland lobes, each with a large nucleolus and nucleus.
Two large nucleated esophago-intestinal cells lie at the
dorsal base of the metacorpus at the junction with the
intestine. The labial disc and lips are prominent and
prorrude from the regular body contour (Figs 1 A; 2 A,
C). The slit-like stoma is located in the oval-shaped
prestoma, which is situated centrally on the labial disc
and surrounded by six small pore-like openings of the
inner labial sensilla (Fig. 2 C). The labial disc is raised
above the surrounding lips. The subventral and sub-
dorsallip pairs are separate and do not fuse to form one
dorsal and one ventral lip. These lips are often termed
medial lips because specimen orientation is difficult ta
discern in the SEM. The laterallips are large and fused
with the lateral edges of the medial lips. Large elongate
oval-shaped openings of the amphids separate the labial
disc and laterallips. A distinct head annule is apparently
348
absent. The stylet is slender, but the knobs are large and
rounded, and often slope posteriorly (Fig. 2 A-B). The
cone gradually increases in width posteriorly and over-
laps the shaft, which also widens gradually posteriorly.
The perineal pattern of M. brevicaudais quite distinc-
tive (Fig. 3). The striae are smooth, coarse, and contin-
uous; they completely encircle the perineum and extend
anteriorly for some distance. The dorsal arch is high and
squarish to rounded. The lateral fields are usually in-
distinct, but they may be marked by irregularities
(Fig. 3 A), or small, wing-like projections (Fig. 3 D). The
striae may completely encircle the large, rounded tail
terminus.
MALES
The slit-like stoma of the male of M. brevicauda is
located in the ovate prestoma which is surrounded by six
small, pore-like openings of the inner labial sensilla
(Fig. 4 A-C). Some of the sensilla may open into the
Fundam. appl. NemalOl.
Morph%gy of Meloidogyne brevicauda
Fig. 2. Me/oidogyne brevicauda Loos, 1953 females; light (LM) and scanning electron micrographs (SEM) A: LM of stylet and
head. B : SEM of excised stylet. C : SEM of face view of head.
prestoma, rather than on the labial disc (Fig. 4 B). The
large, round labial disc is separated from the lips by a
deep indentation which is obvious in both LM and SEM
(Fig. 4 A, D). The large subdorsal and subventral lip
pairs are fused and form one dorsal and one ventrallip.
They extend posteriorly and lie next to the first body
annule. The laterallips are also large and adjacent to the
first body annule. Head annulations are absent.
The lips are set off from the body annulations because
the diameter of the lips is larger than that of the first
body annule. The first body annule is also narrower than
the remaining body annules (Fig. 4 A, C). The tail is
marked by a crescent-shaped fold in the cuticle sur-
rounding the posterior portion of the cloacal opening
(Fig. 4 E-F).
SECOND-STAGE JUVENILES
The slit-like prestoma is located in the ovate prestoma
in second-stage juveniles of M. brevicauda (Fig. 5 A-C).
Six pore-like openings of the inner labial sensilla sur-
round the prestoma. The labial disc is squarish to
rectangular and connected to the mediallips by a narrow
piece of cuticle. The subdorsal and subventral lips are
fused and form one dorsal and ventral lip. They extend
posteriorly, and may be indented medially (Fig. 5 C).
These large medial lips are apparent in both LM and
Vol. 15, nO 4 - 1992
SEM (Fig. 5 A, D). The lateral lips are also large and
adjacent to the first body annule. The amphidial open-
ings appear as small elongate oval openings between the
labial disc and medial lips. Head annulations are absent.
The tail of second-stage juveniles of M. brevicauda is
broad and short (Figs 1 B-E; 5 F-G). It is marked by
transverse grooves that radiate from the posterior end of
the lateral field. The tail has a clear hyaline portion that
is nearly one-third of its length. The phasmids open on
the ventral edge of the lateral fields, nearly midway
between the anus and tail tip (Fig. 1 B-E).
Discussion
The original description of M. brevicauda is very
detailed. The drawings are similar to the morphology
revealed by SEM. Only a few features were clarified by
additional examinations of females, males, and second-
stage juveniles.
Our observations of females are very similar to those
in the original (Loos, 1953). The description of the
medial and lateral lips agrees with our observations in
almost every detail. The morphology of the stoma,
prestoma, and inner labial sensilla are additional features
revealed by SEM. Likewise, the shape of the lips and the
labial disc are clarified. Observations of perineal patterns
349
J. D. Eisenback & N. Gnanapragrasam
Fig. 3. Meloidogyne brevicauda Loos, 1953; perineal patterns. A : SEM; 8-D : Iight micrographs.
350 Fundam. appl. Nematol.
Morphology of Meloidogyne brevicauda
Fig. 4 Meloidogyne brevicauda Loos, 1953 males. Light (LM) and scanning electron micrographs (SEM). A-C : SEM of head in
laterai, face, and medial views, respectively; D : LM of head in lateral view; E-F : SEM of protruded spicules in lateral view and
retraeted in ventral view, respeetively; note the (wo pore-like openings on the tips of the spicules and the foid in the cuticle posterior
ta the cloacal opening.
by SEM and LM show additional morphological fea-
tures and sorne of the variability among specimens.
The external morphology of the anterior end of
females of M. brevicauda is quite different from that of
the four most common species of root-knot nematodes,
M. arenaria, AI. hapla, M. incognita, and M. javanica
(Eisenback el al., 1983). In most species the labial disc is
fused with the medial Eps, but in M. brevicauda, the
labial disc is distinctly separated from the Eps by a deep
Vol. 15, nO 4 - 1992
groove in the cuticle. Usually, the medial lips are fused
into one dorsal and one ventral Ep; in M. brevicauda,
however, they are distinctly separate. Likewise, a distinct
head annule that may be further divided by irregular or
incomplete annulations is commonly present on the
anterior end of root-knot females, but it is absent in
M. brevicauda. The internai morphology is quite similar
to that of most Meloidogyne species (Eisenback, 1984).
The original description and drawings of males of
351
J. D. Eisenback & N. Gnanapragrasam
Fig. 5. Me/oidogyne brevicauda Loos, 1953, second-stage juveniles; Iight (LM) and scanning electron micrographs (SEM). A-C :
SEM of head in nearly lateral, face, and medial views, respectively; 0 : LM of head in lateral view; E : SEM of excised stylet; F :
LM of tail; G : SEM of tail showing lateral field, and anal (upper arrow) and phasmidial opening (Iower arrow).
M. brevicauda were very similar to our observations. The
labial disc and lips appeared more set-off and the stylet
was thinner and more delicate than was illustrated
previously. Likewise, the laterallips were thought to fuse
with the medial lips in Figure 1 F of the original
description, but SEM revealed that they are separate
structures (Fig. 4 C). Also, the crescent-shaped fold
posterior to the cloacal opening was not reported by
Loos (1953).
352
The shape of the head of males of M. brevicauda is
very different from that of most root-knot males (Eisen-
back & Hirschmann, 1980; Jepson, 1984). The labial
dise of most males of Meloidogyne is fused with the
medial lips, but in M. brevicauda, the labial dise is
distinetly separated from them by a deep groove. Fur-
thermore, most root-knot males have a large head annule
that may be further divided by irregular or ineomplete
annulations. Males of M. brevicauda do not have a head
Fundam. app/. NemalOl.
region; the lips are immediately adjacent to the first body
annule, similar to that of Meloinema kerongense Choi &
Geraert, 1974 as observed by Coomans and De Grisse
(1981). The lips of males of Meloidogyne propora Spaull,
1977 also appear to be adjacent to the first body annule
(Spaull, 1977).
The crescent-shaped fold surrounding the cloacal
opening posteriorly does not occur in males of the most
common species (Eisenback & Hirschmann, 1981; Jep-
son, 1987). Other species of rootknot known to possess
a similar cuticular structure include only M. nataliei
Golden, Rose, & Bird, 1981 (Golden el al., 1981) and
M. propora (Spaull, 1977). This fold may be present in
other species, but it is only clearly visible by SEM.
Drawings of second-stage juveniles of M. brevicauda
in the original publication are similar to our LM and
SEM observations. The head labial dise is distinctly
set-off from the lips, and the lips are clearly illustrated
(Loos, 1953). As revealed by SEM, the medial lip pairs
are fused to forro one dorsal and one ventrallip, and they
are distinctly separated from the lateral lips and the
labial dise. AlI of the lips extend posteriorly to the first
body annule; whereas in most other second-stage juve-
niles of root-knot nematodes, a large head annule lies
posterior to the lips. This head annule may be smooth,
or interrupted by irregular or incomplete annulations
(Eisenback & Hirschmann, 1979).
The tail of second-stage juveniles of M. brevicauda is
very different from the four common species named
above. The very short tail is the character from which the
species name was derived. The location of the phasmi-
dial opening on the ventral edge of the lateral field is
most unusual because in other root-knot species it
generally occurs in the middle of the field.
The morphology of M. brevicauda is quite different
from four common species and most other species that
have been examined c1osely. Its morphology is similar in
many respects to M. coffeicola Lordello & Zamith, 1960,
M. indica Whitehead, 1968, M. propora, and M. nalaliei.
Additional studies on the cytology, biology, and host-
parasite relationship of M. brevicauda are necessary for
the proper placement of this species in the genus Meloi-
dogyne.
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Additional notes on the morphology of Meloidogyne brevicauda

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