A review of the enus Amphimonhystera Allgén, 1929 (Monhysterida: Xyalidae, Marine Freeliving Nematodes) with description of three new species
Author
Tchesunov, Alexei V.
Author
Mokievsky, Vadim O.
text
Zootaxa
2005
1052
1
20
journal article
10.5281/zenodo.170014
21e45804-ff76-4aa4-b82b-9d456d5ea2e8
11755326
170014
Amphimonhystera pallida
Tchesunov et Mokievsky
sp. n.
(
Figure 7
)
Type
material:
Holotype
male 1 (ref # M1/1),
paratype
male 2 (ref # M1/2) and
paratype
female 1 (ref # M1/8) mounted in glycerin on glass slides.
Type
specimens are deposited in the collection of the P. P. Shirshov Institute for Oceanology, Russian Academy of Sciences, Moscow.
Type
locality
: Arctic Ocean, area between
Greenland
and
Svalbard
,
79°8.2' N
&
02°53.6' E
, depth
5569 m
(Molloy Deep), silt,
16 August
, 2000.
Etymology
: The species name reflects the pale colouration of the species in comparison with some other brownish
Amphimonhystera
species.
Morphometric data:
Table 6
.
FIGURE 7
.
Amphimonhystera pallida
.
(A) male 1 (holotype), entire; (B) male 1 (holotype), esophageal region; (C) male 1 (holotype), cephalic end; (D) male 2 (paratype), tail; (E) male 1 (holotype), spicule; (F) female 1 (paratype), entire; (G) female 1 (paratype), anterior end. Scale bars: (A), (B), (D) & (F) 100 µ m; (C), (E) & (G) 10 µ m.
TABLE 6.
Morphometry of
Amphimonhystera pallida
| Specimen Label |
Male 1 (holotype) ARK XVI, St 251 MD 317, 1–2 cm, 63 µm, 1/ 21 |
Male 2 (paratype) ARK XVI, St 251 MD 322, 1–2 cm, 63µm, 1/ 58 |
Female 1 (paratype) ARK XVII, St 125, B 0–1 cm, 125 µm, 1/42 |
| Character L |
655 |
735 |
740 |
| a |
32.7 |
35.0 |
24.8 |
| b c |
5.0 8.3 |
5.5 8.2 |
5.5 8.3 |
| V (%) b.diam.c.s. |
5.0 |
5.0 |
75.8% 7.5 |
| b.diam.am. |
11 |
13 |
12 |
| b.diam.n.r. b.diam.c. |
16 17 |
17 20 |
18 23 |
| diam.midb. a.d.. |
20 15 |
21 15 |
30 17 |
| c.s. c.s. (%) |
3 0.60 |
7 1.40 |
7 0.93 |
| am.w. |
8 |
10 |
? |
| am.l. am.w. (%) |
11 73 |
12 77 |
12? |
| am.l./am.w. dis.am. |
1.4 14 |
1.2 14 |
? 21 |
| st.w. |
2.0 |
2 |
3.5 |
| st.l. spic. chord |
2.0 15 |
2.0 20 |
2.5 |
| spic. arc |
24 |
26 |
|
| c' dist. tail portion (%) |
5.3 27 |
5.9 24 |
5.2 28 |
| termin s.l. |
4 |
5 |
9 |
Description:
Small nematodes with slender, near fusiform to cylindrical body. Cuticle thin, with fine transverse annulation. Subcuticular yellowbrownish granulation weakly developed (mainly in preamphidial and amphidial regions) in males or nearly absent in female. Preamphidial region more or less narrowed. Labial region slightly set off. Inner labial sensilla as poorly visible tiny papillae. Outer labial and cephalic sensilla united in one circle of ten setae of moderate length. Amphidial fovea large, longitudinally oval, with distinct unbroken cuticular edging and without a visible central spot. Somatic sensilla short, scarcely distributed laterally along the body; nearly absent in midgut region.
Buccal cavity small; cheilostoma hemispherical; esophastoma narrow, funnel shaped, with sclerotised walls. Esophagus slender, weakly muscular, gradually widening to the posterior end. Cardia small, triangular, internal. Midgut with distinct internal lumen and peritrophic membrane. At a short distance posterior to the cardia, the midgut shifted dorsally by a cell body which may be a pseudocoelomocyte or cell body of a rudimental renette cell. Anterior portion of the female branch situated left of the intestine, posterior portion right of the intestine. Uterus with two ripe eggs. Vulva as a small transversal slit. No vulval glands discernible. Anterior strait testis poorly discernible; posterior testis not visible at all. Two ejaculatory glands left of the
vas deferens
and intestine in the
paratype
male. Spicules short and slender, sharply bent in the middle, distally acute and proximally cephalated. No gubernaculum. Tail with a proximal conical and a distal slender cylindrical portion. Tail tip slightly inflated, with two or three terminal setae. No other somatic setae visible in tail region.
Diagnosis:
Body pale, 655–740 µm long. Outer labial and cephalic setae 3.0–7.0 µm long. Amphidial fovea, 11–12 µm long; ratio length to width of the amphidial fovea 1.2– 1.4 µm; distance from cephalic apex to anterior rim of the amphidial fovea 14–21 µm. Spicules 24–26 µm long. Terminal caudal setae 4.0–9.0 µm long.
Differential diagnosis:
Amphimonhystera palida
sp. n.
is similar
to
A. galea
,
A. marisalbi
and
A. molloyensis
in body size. However,
A. pallida
differs from
A. galea
by having a much shorter cephalic setae length and shorter spicules; from
A. marisalbi
by a greater distance apexamphidial fovea and longer terminal caudal setae; and from
A. molloyensis
by a greater distance apexamphidial fovea.