Description of two new and six known amphidelphic species of the genus Dorylaimoides Thorne and Swanger, 1936 (Nematoda: Dorylaimida: Tylencholaimoidea) from the Tropical Rainforest, Western Ghats, India
Author
Islam, Md Niraul
Author
Ahmad, Wasim
text
Journal of Natural History
2022
2022-06-13
56
5 - 8
311
347
http://dx.doi.org/10.1080/00222933.2022.2049390
journal article
83505
10.1080/00222933.2022.2049390
ea9fe115-7dac-44f4-82d0-7de4dc9bbb90
1464-5262
6758368
2AEDEBA5-69C9-4630-B4BE-C109B6B0D270
Dorylaimoides brevicaudatus
sp. nov.
(
Figures 8
and
9
;
Table 7
)
Description
Female.
Slender nematode of small to medium size,
0.99–1.1 mm
long, slightly ventrally curved to open C-shaped upon fixation; tapering gradually towards both extremities. Cuticle with two distinct layers, 1.5–2.0 μm thick at anterior to midbody and 2.0–3.0 μm at tail. Outer cuticle thin, with fine transverse striations; inner layer thick, distinctly striated. Lateral chords 5.0–7.0 μm at midbody, occupying about onefifth (17–21%) of corresponding body diameter. Lateral, ventral and dorsal body pores indistinct. Lip region cap-like, narrow, almost continuous or offset by slight depression, 1.5–1.8 times as wide as high or about one-fourth of the body diameter at neck base. Lips rounded, amalgamated, inner part slightly raised. Amphids cupshaped, their aperture occupying about two-thirds to three-fourths of lip region diameter. Stoma a truncate cone. Odontostyle short, asymmetrical, 0.85–1.1 times the lip region diameter long, ventral arm 5.0–5.5 µm, dorsal arm 6.0–6.5 µm, its aperture small, about one-seventh to one-fifth of the odontostyle length. Odontophore arcuate, about 1.3–1.6 times the odontostyle length. Guiding ring simple, refractive, at 0.6–0.7 times lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding gradually, into a short, cylindrical basal bulb, 3.2–4.2 times as long as wide, 1.4–1.7 times corresponding body diameter, occupying about 24–28% of total neck length. Pharyngeal gland nuclei visible. Nerve ring at 43–53% of neck length from anterior end. Cardia rounded to conoid, about one-fourth to one-third of the corresponding body diameter long. Genital system didelphic-amphidelphic. Ovaries reflexed, measuring 69– 89 μm (anterior) and 68–89 μm (posterior) long; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 53–88 μm (anterior) and 56–75 μm (posterior), consisting of a slender distal part and a welldeveloped
pars dilatata
. Oviduct-uterus junction marked by well-developed sphincter. Uterus short and tubular, measuring 39–81 μm (anterior) and 39–70 μm (posterior). Sperm cells present throughout the genital tract. Vagina cylindrical, extending inwards, 14.0–17.0 μm or about one-half to three-fifths (47–59%) of midbody diameter;
pars proximalis vaginae
9.0–11.5 × 7.0–9.0 μm, encircled by circular muscles;
pars distalis vaginae
short, 3.0–4.0 μm with slightly curved walls;
pars refringens
absent. Vulva apparently a transverse slit. Prerectum 2.0–4.0 and rectum 0.9–1.0 times anal body diameter long. Tail short, cylindrical, convex-conoid with rounded terminus, 0.7–0.8 times anal body diameter long, with a pair of caudal pores on each side.
Figure 8.
Dorylaimoides brevicaudatus
sp. nov.
(a) Entire female; (b) entire male; (c) anterior region; (d) anterior region showing amphid; (e) pharyngeal region; (f) pharyngeal bulb; (g) female genital system; (h) female posterior region; (i, j) male posterior region.
Figure 9.
Dorylaimoides brevicaudatus
sp. nov.
(LM photographs). (a, b) Anterior region; (c) anterior region showing amphid; (d) pharyngeal region; (e) expanded part of pharynx; (f) female genital system; (g) vulval region; (h) female posterior region; (i, j) female posterior end; (k, l) male posterior end. Scale bars: a–c, e, g–l = 10 μm; d, f = 20 μm.
Table 7.
Morphometrics of
Dorylaimoides brevicaudatus
sp. nov.
All measurements are in μm and in the form mean ± standard deviation (range).
Holotype |
Characters |
female |
Paratype females |
Paratype males |
n |
5 |
6 |
L |
1071 |
1083.0 ± 62.7 (991–1162) |
1035.6 ± 70.5 (972–1157) |
Body diameter at neck base |
27.5 |
28.9 ± 1.6 (26.5–31.5) |
26.4 ± 2.1 (23.5–29.5) |
Body diameter at midbody |
32.0 |
31.1 ± 2.2 (28–34) |
28.0 ± 2.3 (24.5–31.0) |
Body diameter at anus |
19.5 |
19.9 ± 0.73 (18.5–20.5) |
18.2 ± 0.73 (17.5–19.5) |
a |
33.4 |
34.0 ± 1.7 (32.2–37.6) |
36.2 ± 2.1 (34.2–39.8) |
b |
6.4 |
6.3 ± 0.38 (5.7–6.9) |
6.1 ± 0.38 (5.8–6.9) |
c |
64.2 |
68.6 ± 6.1 (64.2–79.0) |
64.0 ± 2.7 (62.0–69.4) |
c’ |
0.8 |
0.76 ± 0.04 (0.71–0.85) |
0.84 ± 0.04 (0.78–0.94) |
V |
49.6 |
47.8 ± 1.4 (47.0–51.2) |
– |
G1 |
16.7 |
12.4 ± 2.2 (10.1–16.4) |
– |
G2 |
14.6 |
11.7 ± 1.7 (10.1–14.3) |
– |
Lip region diameter |
8.0 |
7.4 ± 0.60 (7.0–8.0) |
7.8 ± 0.28 (7.5–8.0) |
Lip region height |
4.5 |
4.2 ± 0.23 (4.0–4.5) |
4.2 ± 0.23 (4.0–4.5) |
Amphidial aperture |
6.0 |
6.0 |
6.2 ± 0.23 (6.0–6.5) |
Odontostyle length |
8.0 |
7.7 ± 0.33 (7.5–8.5) |
7.7 ± 0.18 (7.5–8.0) |
Ventral arm length |
5.5 |
5.3 ± 0.2 (5.0–5.5) |
5.4 ± 0.43 (5.0–6.0) |
Dorsal arm length |
6.5 |
6.2 ± 0.2 (6.0–6.5) |
6.1 ± 0.24 (6.0–6.5) |
Odontophore length |
12 |
11.6 ± 0.59 (10.5–12.5) |
12.4 ± 0.46 (12–12.5) |
Total stylet length |
20 |
19.4 ± 0.46 (18.5–19.5) |
20.1 ± 0.43 (19.6–20.5) |
Guiding ring from anterior end |
5.0 |
5.2 ± 0.18 (5.0–5.5) |
5.1 ± 0.37 (5.0–6.0) |
Nerve ring from anterior end |
83 |
81.9 ± 2.2 (77–84) |
83.1 ± 2.9 (78–88) |
Neck length |
165 |
167.0 ± 13.0 (151–192) |
164.8 ± 4.0 (157–168) |
Expanded part of pharynx |
43 |
44.7 ± 2.6 (42–50) |
44.9 ± 2.7 (42–50) |
Cardia length |
7.0 |
7.6 ± 0.39 (7.0–8.0) |
8.6 ± 0.73 (8.0–10) |
Anterior genital branch |
179 |
137.2 ± 23.9 (113–179) |
– |
Posterior genital branch |
156 |
129.1 ± 17.5 (102–156) |
– |
Vaginal length |
15.0 |
16.0 ± 1.1 (14–17) |
– |
Vulva from anterior end |
532 |
535.5 ± 35.1 (478–588) |
– |
Prerectum length |
72 |
72.0 ± 8.7 (54–83) |
77.0 ± 11.5 (54–90) |
Rectum length |
19.5 |
19.6 ± 0.98 (18–21) |
27.2 ± 1.9 (24.5–29.5) |
Tail length |
16.5 |
15.5 ± 0.87 (15–17) |
15.8 ± 0.67 (15–16.5) |
Spicule length |
– |
– |
27.6 ± 1.9 (24.5–30) |
Lateral guiding pieces |
– |
– |
7.5 ± 0.46 (7–8) |
Ventromedian supplements |
– |
– |
5–7 |
Male.
General morphology similar to that of female except for posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cells spindleshaped, 6.0–8.0 μm long. In addition to adcloacal pair, situated at 7.0–9.0 µm from cloacal aperture, there are five to eight irregularly spaced ventromedian supplements, first ventromedian beginning at level with the head of spicules. Spicules typically dorylaimoid, curved ventrad, slender, 5.4–7.7 times as long as wide and 1.4–1.7 times as long as cloacal body diameter, dorsal contour regularly convex, ventral contour bearing a moderately developed hump and hollow, curvature 128–135°, head occupying 9–10% of total spicules’ length, median pieces 16–20 times as long as wide, occupying about 30–37% of the spicules’ maximum width, reaching the spicules’ tip, posterior end 2.0–2.5 μm wide. Lateral guiding pieces distinct, rod-like, about 4.6–5.3 times as long as wide or about onefourth of the spicules’ length. Prerectum 2.9–5.1 and rectum 1.3–1.7 cloacal body diameter long. Tail short, cylindrical, convex-conoid with rounded terminus, 0.8–0.9 times the cloacal body diameter, with a pair of distinct caudal pores on each side.
Type habitat and locality
Soil
around the roots of grasses (unidentified) from
Verna
,
South
Goa district
,
Goa State
,
India
; coordinates
15.353583°N
,
73.922278°E
.
Type specimens
Holotype
female
on slide
Dorylaimoides brevicaudatus
sp. nov.
/1;
paratype
females on slides
Dorylaimoides brevicaudatus
sp. nov.
/2–4;
paratype
males on slides
Dorylaimoides brevicaudatus
sp. nov.
/5–7; deposited with nematode collection of the Department of Zoology, Aligarh Muslim University,
India
.
Etymology
The new species is named
Dorylaimoides brevicaudatus
because of its short tail.
Diagnosis and relationships
Dorylaimoides brevicaudatus
sp. nov.
is characterised by having a slender body,
0.99– 1.1 mm
long; lip region cap-like, almost continuous or offset by slight depression; odontostyle 7.5–8.5 μm, ventral arm 5.0–5.5 µm, dorsal arm 6.0–6.5 µm; odontophore 10.5–12.5 μm long, arcuate; total stylet length 18.5–20.0 μm; pharynx slender with slightly muscular anterior part, expanding gradually into a short, cylindrical basal bulb occupying about 25–30% of total neck length; female genital system didelphic-amphidelphic; tail short, convex-conoid with rounded terminus, males with 24.5–30 µm long spicules, lateral guiding pieces and 5–7 irregularly spaced ventromedian supplements.
In the presence of short expanded part of pharynx and short, rounded to conoid tail, the new species resembles
D. cameroonensis
Ahmad et al., 2003
and
D. parateres
Siddiqi, 1964
but differs from the former in having a long and slender body (L = 0.91–1.1 vs
0.76– 0.87 mm
, a = 33–39 vs 25–29), narrower lip region (7.0–8.0 vs 9.0–11 μm), shorter odontostyle (7.5–8.5 vs 10–11 μm) and higher b (5.7–6.9 vs 4.6–5.5) and c (64–79 vs 43– 60) ratios.
The new species differs from
D. parateres
in having a shorter body (L = 0.9–1.1 vs
1.2– 1.6 mm
), slightly posterior vulva position (V = 47–51 vs 39–48), lower c’ ratio (0.7–0.9 vs 1.0–1.5), shorter and differently shaped tail (15–17 vs 27–29 μm long, convex-conoid to rounded vs rounded to hemispheroid) and smaller spicules (24.5–30 vs 35–36 μm).
In the presence of amphidelphic gonads and a short tail, the new species also resembles
D. indicus
Jairajpuri, 1965
and
D. teres
Thorne and Swanger, 1936
, but differs from the former in having a shorter body (L = 0.9–1.1 vs
1.1–1.8 mm
), shorter pharyngeal expansion (41–50 vs 64 μm or 24–30 vs 31% of total neck length), slightly posterior vulva position (V = 47–51 vs 39–47), shorter tail (15–17 vs 18–26 μm) and smaller spicules (24.5– 30 vs 38 μm).
The new species differs from
D. teres
in having a comparatively shorter body (0.9–1.1 vs
1.1–1.6 mm
), differently shaped and narrower lip region (conoid vs rounded, 7.0–8.0 vs 9.0–10 μm), shorter pharyngeal expansion (41–50 vs 51–63 μm), slightly posterior vulva position (V = 47–51 vs 40–48), shorter tail (15–17 vs 21–30 μm) and smaller spicules (24.5– 30 vs 35–38 μm).