Ohbayashinema erbaevae, Durette-Desset & Ganzorig & Audebert & Kamiya, 2000

Durette-Desset, Marie-Claude, Ganzorig, Sumyia, Audebert, Fabienne & Kamiya, Masao, 2000, A new species of the genus Ohbayashinema (Nematoda, Trichostrongylina, Heligmosomoidea), parasite of Ochotona daurica (Ochotonidae, Lagomorpha) from Buriatia, Zoosystema 22 (4), pp. 667-676 : 669-674

Ohbayashinema erbaevae n. sp.

( Figs 1-3 )

TYPE MATERIAL. — Holotype, allotype, MNHN 41 MHa; 24, 34 paratypes, MNHN 41 Mhb (7 th experimental generation, collected at D15 post infestation, 24.XI.1998).

ETYMOLOGY. — After the name of Dr M. Erbaeva, specialist of the paleontology of the Ochotonidae .

GEOGRAPHICAL ORIGIN. — Kudara Somon (107°E, 51°N), Buriatia.

HOST. — Ochotona rufescens rufescens (Gray, 1842), (Ochotonidae) (experimental host).

SITE. — Duodenum (SI 1).

VOUCHER MATERIAL. — 16, 32, 6 L4 (MNHN 1ME, 2 ME, 12 ME, 22 ME, 26 ME, 44 ME, 52 ME) from 2 and 5 Ochotona daurica (Pallas, 1776), originating from Kudara Somon (107°E, 51°N), Bouriatia. The worms collect- ed in six pikas were located just behind the pylorus at the beginning of the duodenum and entangled like a ball of wool. In the pika (26 ME) parasitised by 1 and 6 L4, the distribution in the small intestine was the following: SI 2: 1 male, 2 L4; SI 3: 2 L4; SI 4: 2 L4.

DESCRIPTION

Nematodes with marked sexual dimorphism, females being twice to three times longer than males. Anterior part of male coiled along ventral side with two to three sinistral rings. Entire body of female coiled with 16 to 20 very tight sinistral rings. Deirids rounded at their base, with very thin thread, about 10 to 12 long ( Fig. 1D ). Deirids always situated at about same level of excretory pore but varying in position (above, at same level, below excretory pore), not laterally but sligthly displaced to dorsal side. Ratio of oesophagus length to body length greater in female (7% on average) than in male (3% on average). Separation between muscular and glandular oesophagus with varying visibility and situated at level of nerve ring when visible ( Fig. 3B ).

Head

Cephalic vesicle present, slightly assymetrical, dorsal side usually longer than ventral side. In apical view, oval-shaped buccal opening surrounded by small ring; absence of interno-labial papillae, presence of four externo-labial papillae, four cephalic papillae and two amphids. Dorsal oesophageal gland very clear in apical and lateral views ( Fig. 3A, B ).

Synlophe

Studied in two male and two female paratypes. In both sexes, body bearing continous ridges. In transverse sections in median part of body, 14 ridges (stage 7/7) present in male ( Fig. 1F ), 13-14 (stages 7/6, 7/7) in female ( Fig. 2E ). Ridges appearing just before cephalic vesicle, stages being 3/ 4 in male ( Fig. 1A ) and 4/ 3 in female ( Fig. 2A ). Other ridges appearing at different levels between cephalic vesicle and end of oesophagus and reaching stages 9/ 7 in male ( Fig. 1 B-E) and 10/ 7 in female ( Fig. 2B, C ). New ridges appearing always on lateral sides, more numerous on right lateral side. About 100 below oesophagus, lateral ridges disappearing and becoming stage 7/7 ( Fig. 1F ).

Ridges disappearing just above caudal bursa in male, and progressively between level of distal posterior uterine branch and that of vulva, in female ( Fig. 2 F-J).

Dorsal ridges of similar size, smaller than ventral ones, difference more marked in female. Ventral ridges having double decreasing gradient of size from ventral to lateral size, therefore ventral median ridges always more developed; character very prominent in female ( Fig. 2 D-F).

Only lateral oesophageal ridges orientated perpendicularly to body wall, other ridges orientated from right to left side according to a frontal axis of orientation in male, sub-frontal in female. No ridges in front of lateral fields ( Figs 1 A-H; 2A-J).

Holotype male

9 mm long, width increasing gradually from 90 at level of oesophago-intestinal junction, to 130 at mid-body, then decreasing to 120 just above caudal bursa. Cephalic vesicle 75 (ventral side) 85 (dorsal side) long and 40 wide. Nerve ring, excretory pore and deirids at 190, 400 and 412 from apex, respectively. Oesophagus 580 long i.e. 6.4% of body length ( Fig. 3B ).

Caudal bursa assymetrical, of 2- 3 type with right lobe larger ( Fig. 3D ). Prebursal papillae with long peduncle, situated on common trunk of rays 2 to 6 and not anterior to caudal bursa (visibility of papillae varying according to specimens). Rays 3 strongly developed. Rays 6 arising from lateral trident before separation of rays 4 and 5. Rays 8 slightly sinuous, not arising on dorsal ray but on common trunk of rays 2 to 6. Distance between extremities of dorsal ray and right ray 8 shorter than that of those between dorsal ray and left ray 8. Very short dorsal ray, divided into two branches in its distal third. Each branch divided into three branchlets (rays 9 [external], rays 10 and phasmids [internal]). In holotype ( Fig. 1I ) and four paratypes ( Fig. 1J ), rays 9 arising from dorsal ray at same level as division of latter. In five other paratypes, rays 9 arising after division of dorsal ray ( Fig. 1 K-M) According to specimens, phasmids (situated between rays 9 and 10) may be visible. Dorsal ray enclosed in membrane reaching rays 8. Thin, alate spicules, 530 long, i.e. 5.9% of body length. Chitinoid axis of each spicule doubled for almost whole length of spicule. Only distal extremities single, 15 long and sharp. In dissected spicules, tips not joined ( Fig. 3 D’). Well-developed genital cone, bearing on dorsal lip, leaf-shaped papillae 7 with extremity ventrally curved and enclosed in membrane ( Fig. 1N ). Papilla 0 not observed.

Measurements of nine paratype males given in Table 1.

Allotype female

21.8 mm long, width increasing gradually from 120 at level of oesophago-intestinal junction to 200 at mid-body, 250 at level of median part of uterine branch, then decreasing to 210 below level of vulvar opening. Cephalic vesicle 100 (ventral side) 110 (dorsal side) long and 50 wide. Nerve ring, excretory pore and deirids at 250, 560 and 575 from apex, respectively. Oesophagus 780 long i.e. 3.5% of body length.

Monodelphic with atrophied, non functional, posterior genital branch, 180 long. Vulvar opening 410 from posterior extremity. Vagina vera 60 long, directed anteriorly obliquely. Ovejector with vestibule 560 long, sphincter 60 long and 65 wide, infundibulum 200 long. Vestibule divided into three distinct parts: enlarged proximal part, thin rectilinear median part of equivalent length to proximal part, shorter distal part either strongly swollen, bulbous (allotype and seven paratypes) ( Fig. 3E, F ) or only enlarged like proximal part (two paratypes) ( Fig. 3C, G ). Infundibulum usually straight, directed anteriorly in continuity with sphincter and vestibule ( Fig. 3E ), or directed posteriorly in one paratype ( Fig. 3C ). Uterus 4.5 long, i.e. 20.6% length of body, with numerous eggs (over 200), morula stage, 80 long and 50 wide. In three paratype females, presence of a vulvar “plug”. Tail 100 long with caudal spine 10 long ( Fig. 3H ).

Main measurements of nine paratype females given in Table 1.

Figures

FIG. 1. — Ohbayashinema erbaevae n. sp. in Ochotona r. rufescens, male; A-H, male 10 mm long, transverse sections of the body; A, at 40 µm from apex, stage 3/4; B, at 160 µm from apex, stage 5/5; C, at 200 µm from apex just before level of excretory pore, stage 6/5; D, at level of left deirid, stage 8/6; E, at oesophago-intestinal junction, stage 9/7; F, at mid-body (4.5 mm from apex), stage 7/7; G, at 3.8 mm above caudal bursa, stage 6/7; H, at 200 µm from caudal bursa, stage 2/5; I-M, male, caudal bursae, different patterns of rays 8 and dorsal ray; I-K, dorsal views; K, holotype male; L, M, ventral views; N, genital cone and papillae 7, ventral view; O, detail of the excretory pore and the deirids, ventral view. All the sections of the body are orientated as G. Arrows indicate the origin of the new ridges. Abbreviations: d, deirid; l, left side; v, ventral side. Scale bars: A-E, 50 µm; F-H, 100 µm; I-M, 150 µm; N, O, 30 µm.

FIG. 2. — Ohbayashinema erbaevae n. sp. in Ochotona r. rufescens, female 24.9 mm long, transverse sections of the body; A, just behind cephalic vesicle, stage 4/3; B, at level of the nerve ring, stage 6/4; C, at level of the oesophago-intestinal junction, stage 10/7; D, at 5.7 mm from apex, stage 7/7; E, at mid-body (11.4 mm from apex), stage 7/6; F, at the level of the proximal uterine branch, stage 5/6; G, at the junction between the median and the distal parts of the vestibule, stage 5/5; H, at the level of the median thin part of the vestibule, stage 5/5; I, at the level of the proximal part of the vestibule, stage 3/3; J, at the level of the posterior atrophied uterine branch, stage 3/0. All the sections of the body are orientated as in F. Arrows indicate the origin of the new ridges. Abbreviations: agb, atrophied genital branch; l, left side; v, ventral side. Scale bars: A, B, 50 µm; C-F, 150 µm; G-J, 75 µm.

FIG. 3.— Ohbayashinema erbaevae n. sp. in Ochotona r. rufescens; A, female,head, apical view;B, male, anterior extremity,right lateral view; C, female, posterior extremity, right lateral view; D, male, caudal bursa, ventral view; D’, detail of the tip of a spicule; E, other female, posterior extremity, right lateral view; F, female E, detail of the ovejector with bulbous distal part of the vestibule and the atrophied posterior branch;G, female C,detail of the ovejector with enlarged distal part of the vestibule and the atrophied posterior branch; H, female caudal extremity and tip,ventral view. Abbreviations: ve, vestibule;1, enlarged proximal part; 2, thin rectilinear median part; 3, shorter distal part;agb, atrophied genital branch. Scale bars:A, 30 µm; B, C, E-G,200 µm; D, 150 µm;D’, 50 µm; H, 100 µm.