Measurements (After Stone, 1973, type population)
25 females: Stylet length = 27.4 +
1.1 u; head width at base = 5.2 + 0.5 u; stylet base
to dorsal gland duct entry = 5.4 + 1.1 u; head tip to median
bulb valve = 67.2 + 18.7 u; median bulb valve to level of
excretory pore = 71.2 + 21.9 u; head tip to level of excretory
pore = 139.7 + 15.5 u; mean diameter of median bulb = 32.5
+
4.3 u; mean diameter of vulval basin = 24.8 + 3.7 u;
length of vulval slit = 11.5 + 1.3 u; anus to vulval basin
= 44.6 + 10.9 u; number of cuticular ridges on anal-vulval
axis = 12.5 + 3.1.
25 Cysts: Width = 534 + 66 u;
length excluding neck = 579 + 70 u; neck length 118 +
20 u; mean fenestral diameter = 24.5 + 5.0 u; anus
to fenestra distance = 49.9 + 13.4 u; Granek's ratio (Granek,
1955) = 2.1 + 0.9.
25 males: Body length = 1198 +
104 u; body width at excretory pore = 28.4 + 1.3 u;
head width at base = 12.3 + 0.5 u; head length = 6.8 +
0.3 u; sylet lenght = 27.5 + 1.0 u; stylet base to
dorsal gland duct entry = 3.4 + 1.0 u; head tip to median
bulba valve = 96.0 + 7.1 u; median bulb valve to excretory
pore = 81.0 + 10.9 u; head tip to excretory pore = 176.4
+
14.5 u; tail length = 5.2 + 1.4 u; tail width at anus
= 13.5 + 2.1 u; spicule length along axis = 36.3
+
4.1 u; gubernaculum length = 11.3 + 1.6 u.
50 Second-stage larvae: L = 486
+ 23 u; body width at excretory pore = 19.3 + 0.6 u;
head width at base = 10.6 + 0.5 u; head length = 5.5 +
0.1 u; stylet length = 23.8 + 1.0 u; stylet base to
dorsal gland duct entry = 2.7 + 0.9 u; head tip to median
bulb valve = 68.7 + 2.7 u; median bulb valve to excretory
pore = 39.9 + 3.3 u; head tip to excretory pore = 108.6 +
4.1 u; tail length = 51.1 + 2.8 u; tail width at anus
= 12.1 + 0.4 u; length of hyaline tail = 26.6 + 4.1 u.
Holotype larvae: L = 510 u;
body width at excretory pore = 19 u; tail length = 53 u;
hyaline tail length = 31 u; tail width at anus = 13 u; head
annules = 4; head height = 5 u; head width = 9 u; stylet
length = 25 u; stylet base to dorsal gland duct entry = 2 u;
head tip to median bulb valve = 74 u; median bulb valve to excretory
pore = 32 u; head tip to excretory pore = 106 u.
Description Female: Body sub-spherical with a projecting neck bearing the
head and containing the oesophagus and part of the oesophageal glands.
Colour white, some populations passing through a 4-6 week cream stage,
turning glossy brown when dead (Guile, 1966, 1967, 1970). Head with
amalgamated lips and one or two prominent annules, deep irregular annulations
on the neck, changing to reticulate pattern of ridges over most of the
body surface. Lateral incisures absent. Head skeleton weakly
developed, hexaradiate. Anterior part of stylet about 50% of total
stylet length and frequently separated from posterior part in fixed specimens.
Stylet knobs backward sloping. Stomal lining forming a tube-shaped
"stylet guide" extending from head skeleton to about 75% of stylet length.
Very large median oesophageal bulb, almsot circular with large crescentic
valve plates. Lobe of oesophageal glands broad, frequently displaced
forwards; 3 nuclei. Prominent excretory pore situated at base of
neck. Internal structures in neck region often obscured by hyaline
secretions on cuticle surface. Ovaries paired, occupying most of
body cavity. Vulva a transverse slit at the opposite pole of body
to neck, set in a slight circular depression, the vulval basin. Vulval
orifice set between two finely papillated crescentic areas (Green, 1971)
occupying most of the vulval basin. Cuticle surface between anus
and vulval basin thrown into about 12 parallel ridges with a few cross
connections. Sub-surface punctations, irregularly arranged, are visible
over much of body surface and may be confused with surface papillae on
the vulval crescents.
Cyst: New cysts glossy brown in colour, subspherical with protruding
neck. Head frequently lost leaving terminus of neck open. Vulval
region intact or fenestrated with single circumfenestrate opening occupying
all or part of the vulval basin. Vulval bridge, underbridge and other
remains of internal genitalia absent. Abullate, but small darkened
or thickened "vulval bodies" sometimes present in the vulval region. Anus
visible in most specimens, often at apex of a V-shape mark. Cuticular
pattern as in female, but more accentuated. Sub-crystalline layer
absent.
Male: Vermiform body with short tail ending in bluntly
rounded terminus of variable shape. Heat relaxed specimens C- or
S-shaped, posterior part twisted 90-180O about
longitudinal axis. Cuticle with regular annulations and 4 incisures
in lateral field, terminating on tail. Annules sometimes crossing
the outer incisures but not the inner pair. Offset, rounded head
with large oral disc, 6 irregular lips, 6 or 7 annules and heavily sclerotized
hexaradiate skeleton. Anterior part of cephalids at 2nd to 4th annules
behind head, posterior pair at 6th to 9th annules. Stylet well developed
with backward sloping basal knobs and anterior part about 45% of total
stylet length. Lining of stoma lyre-shaped anteriorly and forming
a simple tube-shaped "stylet guide" posteriorly to about 70% of stylet
length. Ellipsoid median oesophageal bulb with strong crescentic
valve plates linked to a narrow, ventrally situated oesophageal gland lobe
by a narrow isthmus encircled by a broad nerve ring. Three oesophageal
gland nuclei, the dorsal one most prominent; lobe terminating near excretory
pore about 15% of body length from head. Hemizonid 2 annules long,
situate 2 to 3 annules behind excretory pore. One testis, commencing
with single cap cell 40 to 65% of body length from head and terminating
in a narrow vas deferens with glandular walls. Cloaca with small
raised circular lip containing two stout arcuate spicules terminating distally
in single pointed tips. Small dorsal gubernaculum without ornamentation
2 u thick laterally, slightly wider in dorso-ventral aspect.
Phasmids and caudalids not observed.
Second-stage larva: Vermiform, folded four times within
egg. Tail tapering uniformly with a finely rounded point, body cavity
extending about half way along tail length, remainder forming hyaline tail
region. Regular cuticular annulations. Lateral field with 4
incisures beginning and terminating with 3 and occasionally completely
areolated. Cuticle thickened for first 7 to 8 body annules.
Rounded head slightly offset with 4 to 6 annules. Oral disc surrounded
by 2 lateral lips bearing amphid apertures and dorsal and ventral pairs
of sub-lateral lips which are often fused. Contour of lips and oral
disc sub-rectangular. Heavily sclerotized hexaradiate head skeleton,
the dorsal and ventral radii bifurcate at tips in 60% of specimens.
Anterior cephalids at 2nd to 3rd body annule from head, posterior at 6th
to 8th annule. Stylet well developed, basal knobs with distinct forward
projection on anterior face in lateral view. Anterior part of stylet
approximately 50% of total stylet length. Stomal lining as in male.
Oesophagus and nerve ring as in male. Gland lobe extended posteriorly
for approximately 35% of body length. Excretory pore approximately
20% of body length behind head. Distinct hemizonid 2 annule-widths
long, 1 annule before excretory pore; hemizonian 5 to 6 annules behind
excretory pore. Four-celled gonadial primordium at approximately
60% of body length behind head. Phasmids and caudalids not observed.
Heterodera pallida is very similar to H.
rostochiensis Wollenweber, 1923 and the two species differ consistently
only in the following physical aspects: Larvae of H. pallida usually
larger, stylet longer (21-26 (23.6)u) compared with 21-23 (21.8)u,
body longer (440-525 (484)u) compared with 425-505 (468)u)
and tail longer (46-62 (51.9)u) compared with 42-50 (43.9) u.
Profile of larval stylet knob of H. pallida with anterior face pointed,
rounded in H. rostochiensis. The rectangular contours of oral
disc and lips also distinguish H. pallida larvae from those of H.
rostochiensis which have ovate contours. (Seen in face view with
a scanning electron microscope). Males of H. pallida have
on average a shorted distance between stylet knobs and junction of the
dorsal gland duct than those of H. rostochiensis, 2-7 (3.5) u
and 4-8 (5.3)u respectively. Females of H. pallida
are distinguished from those of H. rostochiensis by their longer
stylets (23-29 (26.7)u) compared with 21-25 (22.9)u, by the shorter anal-vulval
distance (22-67 (43.9)u) compared with 37-77 (60.0)u and by the smaller
number of cuticular ridges between anus and vulva (8-20(12.2)) compared
with 16-31 (21.6). The cream or white internal colour of females
of H. pallida also distinguishes them from H. rostochiensis in which the
colour is golden. Cysts are distinguished by the same cuticular characters
as the female. Because differences in larval morphometrics between
the two species are small, preparation methods which cause dimensional
changes are undesirable. Stone (1971) found that heat relaxation
for 2 minutes at 65O followed by fixation
in cold 4% formalin caused least dimensional change.
Type host and locality Solanum tuberosum L. Epworth, Lincolnshire, England.
(Description Stone, 1973 [from C.I.H. Descriptions of Plant Parasitic
Nematodes, Set 2, No. 17])
Morphology
Sedentary females: smoothly rounded with small projecting
neck, no terminal cone present, diameter + 450 um, ranging
in colour from white to yellow. Cysts are similar in shape, but have
a tanned brown skin. Cuticle surface with zig-zag pattern of ridges,
a distinct D-layer is present. The perineal area consists of a single
circumfenestration around the vulval slit, perineal tubercles on crescents
near vulva. Anus subterminal without fenestra, vulva in a vulval
basin, underbridge and bullae rarely present. Eggs retained in cyst,
no egg-mass present. The non-sedentary second-stage juveniles are
vermiform, annulated and tapering at both ends. Body length ranging
from 445 to 510 um, stylet length 19-25 um, tail length 37-55
um
and a hyaline tail part of 21-31 um. Use of a combination
of cyst and second-stage juvenile characteristics is recommended for reliable
identification. These stages are normally present in most soil samples
infested with potato cyst nematodes.
G. rostochiensis and G. pallida are
morphologically and morphometrically closely related (Stone, 1973).
The most important cyst differences can be obtained from the observation
of the perineal area, i.e. number of cuticular
ridges between vulva-anus and Granek's ratio (the distance from the
anus to the nearest edge of the vulval basin, divided by vulval basin diameter).
The most reliable second-stage juvenile characters are stylet
length and stylet knob shape. Overlap of values takes place,
so care is needed. See
drawings.
(Description from EPPO Standards, 2004)
