The systematic position of some Ethiopian Nippostrongylinae ( Nematoda , Trichostrongylina , Heligmosomoidea ) from the National Collection of Animal Helminths , Onderstepoort , South Africa

DURETTE-DESSET, M.-C. & DIGIANI, M.-C. 2005. The systematic position of some Ethiopian Nippostrongylinae (Nematoda, Trichostrongylina, Heligmosomoidea) from the National Collection of Animal Helminths, Onderstepoort, South Africa. Onderstepoort Journal of Veterinary Research, 72: 55–65 The taxonomic status of some nippostrongyline nematodes deposited in the National Collection of Animal Helminths, Onderstepoort, is revised. Heligmonina boomkeri n. sp. is described from Aethomys chrysophilus from South Africa. The most closely related species by the body measurements and the pattern of the caudal bursa is Heligmonina bignonensis Diouf, Bâ & Durette-Desset, 1997, a parasite of Mastomys erythroleucus from Senegal. It differs from the new species mainly in the number of ventral cuticular ridges at mid-body (four versus five) and the left ala in the male is shorter than the body diameter. The systematic position of Heligmonina spira (Ortlepp, 1939) and Neoheligmonella capensis (Ortlepp, 1939) is confirmed here through their synlophe, which was not previously studied.


INTRODUCTION
The Nippostrongylinae (Heligmonellidae) are parasites of relatively recent appearance, during the Upper Miocene (Durette- Desset 1985).They may have spread throughout the world with the migrations of their hosts, the Muridae.The group lends itself particularly well to molecular studies, the hosts being easy to capture and not considered as rare species in need of protection.A phylogeny of the Trichostrongylina based on morphological features was proposed by Durette-Desset (1985).
However, a comparison of the phylogenies of the Nippostrongylinae based on morphological and on molecular characters, such as the ITS 1 and ITS 2, has not been made.Before embarking upon this work, it was necessary to clarify the systematic position of some species in which the synlophe, the main character used for the determination of a species, is not known or was insufficiently described.This study concerns the species described by Ortlepp (1939) in South Africa.

MATERIAL AND METHODS
The specimens studied originated from the National Collection of Animal Helminths (NCAH), formerly known as the Onderstepoort Helminthological Collection.They are very fragile and, in some, the cuticle was damaged or separated from the body on cross-section.The state of preservation of the speci-mens determined the accuracy of our descriptions, as some features were hardly visible or were absent due to attrition.The nomenclature used for taxa above the family group is that of Durette-Desset (1985) and that for the structures of the caudal bursa is that of Durette- Desset & Chabaud (1981).The cuticular ridges were numbered from left to right for the dorsal and ventral sides, both being delimited by the lateral fields which were always visible.The curve of the left ala is not included in the measurement of its length.Where necessary, this length is compared with the diameter of the body at the level of the lateral fields (Fig. 2A).All measurements are in micrometers except where otherwise stated.The measurements of the female paratypes of the new species are indicated in parentheses.The material of the new species is deposited in the NCAH, Onderstepoort, South Africa and the Helminthological Collection of the Muséum national d'Histoire naturelle, Paris, France (MNHN).The nomenclature of the hosts is that of Musser & Carleton (1993).

GENERAL
Very small nematodes, body curved along the ventral side, anterior end in one or two spirals.Position of nerve ring variable.Excretory pore situated within posterior quarter of oesophagus.Deirids at same level of or posterior to excretory pore (Fig. 1).Oesophagus about 10 % of body length.Left ala longer than body diameter.Very short vestibule slightly longer than sphincter.Ratio of uterus length to body length less than 25 %.

SYNLOPHE
In both sexes the body bears continuous cuticular ridges, appearing just posterior to cephalic vesicle, except left dorsal ridge adjacent to lateral field (no. 1 in Fig. 1C) and disappearing 70 µm anterior to caudal bursa in male (Fig. 1D).In the female, ventral ridges disappear at different levels between the infundibulum and vulva (Fig. 1E-G and 2D-G), dorsal ridges and left ala disappear at about 40 µm from anus (Fig. 1H).Number of ridges: in female, at level of oesophago-intestinal junction, 13 (left hypertrophied ala, six dorsal, six ventral) (Fig. 2C); in both sexes, at mid-body, 12 (left ala, six dorsal, five ventral) (Fig. 2A and B).At mid-body, double gradient of size, decreasing from left to right on ventral side and from right to left on dorsal side.In section, left ala longer than body diameter in male, shorter in female (Fig. 2A and B).At mid-body, absence of ridges on right, ventral-right quarter.At mid-body, axis of orientation directed from ventral right to dorsal left side and inclined at 70 ° on sagittal axis in male, 65° in female (Fig. 2A and B).
Asymmetrical caudal bursa with left lateral lobe more developed and pattern of type 1-3-1 (rays 2 and 6 separating the first from common trunk of rays 2-6) in right lobe and 1-4 (ray 2 separating the first from common trunk of rays 2-6) in left lobe with tendency to type 1-3-1 (Fig. 2I and J).Left lobe: ray 6 arising the first from common trunk of rays 3-6, then ray 3. Ray 4 the most developed, thicker and slightly longer than ray 5. Rays 4 and 5 distally divergent.Ray 6 short (Fig. 2I).Right lobe: ray 5 arising the first from common trunk of rays 3-5.Rays 8 arising proximally on trunk of dorsal ray, left ray longer than right one.Dorsal ray divided into two branches at its proximal third, each branch giving rise to two small branches, rays 9 (external branches) longer than rays 10 (internal branches).Filiform, alate spicules, 418 long with sharp tips (Fig. 2J).Ratio of spicules length/body length: 18.4 %.Gubernaculum not distinct.In one specimen, a slight thickening of the cuticule of the spicular canal may represent this structure (Fig. 1D).Genital cone not visible (see below).
MAIN MEASUREMENTS   terior third of oesophagus.Deirids at same level or posterior to excretory pore (Fig. 3A).Oesophagus less than 7 % of body length in male, 6 % in female.
In male and female, left ala shorter than body diameter.Vestibule twice as long as sphincter.Ratio of uterus length/body length less than 20 %.Eggs in two rows except in distal part of the uterus.

SYNLOPHE
In both sexes, the body bears continuous cuticular ridges, appearing between the cephalic vesicle and excretory pore (Fig. 3B and C), except ridges no.6 and 10' which appear posterior to it.Ridges disappear anterior to caudal bursa in male.In female, ridge no.8' disappears at about 800 anterior to vulva (Fig. 4C), ridges no. 1 and 7' at about 300 anterior to vulva (Fig. 4D), other ridges at different levels between infundibulum and sphincter (Fig. 3D  and E).The left hypertrophied ridge disappears at about 250 from vulva (Fig. 3E).Number of ridges at mid-body: 16 (left ala, six dorsal, nine ventral) in male (Fig. 4A), 15 (left ala, six dorsal, eight ventral) in female (Fig. 4B).Dorsal gradient of size, decreasing from left to right.At mid-body, on ventral side, gradient gradually decreasing from ridge no.2'-5' in male, from no. 2'-4' in female, then ridges of equivalent size.Left ala almost as long as body diameter in both sexes.Presence of ridges on right, right-ventral quarter at mid-body (Fig. 4A-D).Axis of orientation at mid-body directed from right ventral to left dorsal side and inclined on sagittal axis at 60°i n both sexes (Fig. 4A and B).
Asymmetrical caudal bursa with left lateral lobe more developed and pattern of type 1-4 (rays 2 separating the first from common trunk of rays 2-6) (Fig. 4F).Very long rays 3. Rays 3 and 6 arising at same level from common trunk of rays 3-6.Rays 4 and 5 joined in two thirds of their length (right lobe), divergent only at their extremities (left lobe).Rays 8 arising asymmetrically on trunk of dorsal ray.Dorsal ray divided into two branches at its distal quarter, each branch giving rise to two small equal branches, rays 9 (external branches) and rays 10 (internal branches) (Fig. 4F).
Spicules filiform, with sharp tips.It was not possible to measure the spicules and gubernaculum accurately.Very small genital cone, 15 long and 10 wide at base with papilla 0 and papillae 7 well developed (Fig. 4G).

REMARKS
The specimens described above are parasites of Rhabdomys pumilio and were named Heligmospiroides spira by Ortlepp (1939).The characters of the synlophe, not previously described in transversal sections, allows us to confirm that the species belongs to the genus Heligmonina, as proposed by Durette-Desset (1971).In comparing our findings with the detailed description of Ortlepp, we found some differences that we consider as minor, namely that the body and various organs are longer.It is interesting to note that, among the species of the genus, the female of H. spira is the only one in which the anus and the vulva open on the external side of the spire.According to the description of Ortlepp (1939) the male is the only one to have a very complex gubernaculum.

GENERAL
Small nematodes, tightly curved along their ventral side.Excretory pore situated within posterior third of oesophagus.Deirids at same level than excretory pore (Fig. 5A).Oesophagus less than 10 % of body length in male, 6 % in female.In male and female, left ala twice as shorter as the body diameter.Vestibule twice longer than sphincter with constriction at middle.Ratio uterus length/ body length less than 20 %.Eggs in two rows except in distal part of uterus.

SYNLOPHE
In both sexes, the body bears continuous cuticular ridges, appearing just posterior to cephalic vesicle, except dorsal ridge of carene (no. 1) which appears at level of excretory pore.In male, ridges disappear anterior to caudal bursa except ridge no. 4 which disappears within posterior quarter of body (Fig. 5E).In female, dorsal ridges no. 4 and 5 merge at about 400 anterior to vulva.All ridges disappear at level of vulva.Carene with dorsal ridge poorly developed in both sexes, except at the end of the anterior third in male (Fig. 5).Ridge no. 5 (in front of right lateral field) well developed.Number of ridges at oesophageal region (Fig. 5B) and at mid-body (5D and F): 12 (carene, four dorsal, six ventral) in both sexes; in female, at level of infundibulum, 11 (carene, three dorsal, six ventral) (Fig. 5G); just anterior to vulva: 6 (two dorsal, two left and two right lateral) (Fig. 5H).At mid-body, double gradient of size of the ridges.On ventral side, gradient gradually decreasing from left to right, from ridge no.2'-5' then ridges of equivalent size.On dorsal side, except dorsal ridge of carene, gradient gradually decreasing from right to left.In female, ridges no. 1 and 5 most developed.Axis of orientation directed from right ventral to left dorsal side and inclined at about 60° on sagittal axis in both sexes (Fig. 5D  and F).5M).

REMARKS
The specimens described above, parasites of Rhabdomys pumilio were named Longistriata (L.) capensis by Ortlepp (1939).The characters of the synlophe, not described in transversal sections up to now, allow us to confirm that the species belongs to the genus Neoheligmonella, as proposed by Durette-Desset (1971).
Neoheligmonella capensis is distinguished from the other species of the genus by the S-shaped extremity of the spicules.However, the syntypes described here differ from the specimens described by Ortlepp (1939) in two characters, viz. the female tail, which is straight, and the dorsal ray, which is divided in the proximal part rather than at the distal one.This latter feature is usually diagnostic at specific level, and it is possible that the specimens studied here represent a new species.Since all the remaining characters are identical to those described for N. capensis, including the S-shaped extremity of the spicules, we prefer to assign the specimens, at least temporarily, to N. capensis, until such time more material becomes available.
In the genus Neoheligmonella, the caudal bursa is sub-symmetrical except in N. capensis and N. acomysi Durette- Desset & Gibson, 1990 in which the right lobe is clearly more developed than the left one.This character distinguishes the genera Neoheligmonella and Heligmonina Baylis, 1928.In the latter, the asymmetry is always present with a more pronounced development of the left lobe.

FIG. 1
FIG. 1 Heligmonina boomkeri n. sp.A, male, anterior part, left lateral view.B, C, male, origin of the cuticular ridges, right and left lateral views.D-H, posterior part where the ridges disappear.D, male, right lateral view; E-H, female, E, left lateral view, F, right lateral view, G, ventral view, H, dorsal view The ridges are numbered from left to right from no. 1-n for the dorsal side, no.1'-n' for the ventral side Scales: 50 µm FIG. 3 Heligmonina spira(Ortlepp, 1939).A, male, anterior part, ventral view.B, C, female, origin of the ridges, right and left lateral views.D, E, female, area where the ridges disappear, right and left lateral views The ridges are numbered from left to right, no.1-n for the dorsal side, no.1'-n' for the ventral side Scales: A-C: 50 µm; D, E: 100 µm FIG.4Heligmonina spira(Ortlepp, 1939) A-D, synlophe in transverse sections of a male (4.3 mm long) and a female (5.9 mm long).A, male, at mid-body (2.2 mm from the apex); B-D, female, B, at mid-body (2.8 mm from the apex), C, at 800 µm anterior to the caudal extremity, D, at 500 µm anterior to the caudal extremity.E, female, posterior part, right lateral view.F, male, caudal bursa, ventral view.G, male, genital cone, ventral viewThe ridges are numbered from left to right, no.1-6 for the dorsal side, no.1'-10' for the ventral side.The arrows indicate the disappearance of the ridges.All the ridges are orientated as in Fig.4AAbbreviations: r, right side, v, ventral side Scales: A-F: 50 µm; G: 10 µm

FIG. 5
FIG. 5 Neoheligmonella capensis(Ortlepp, 1939) A, male, anterior part, right lateral view.B-H, synlophe in transverse sections of a male (5.2 mm long) and a female (8.9 mm long).B-E, male, B, at the level of the oesophago-intestinal junction, C, at the end of the anterior third of body, D, at mid-body (3.1 mm from the apex), E, at 1.3 mm anterior to the caudal bursa; F-H, female, F, at mid-body (3.4 mm from the apex), G, at the level of the infundibulum, H, just anterior to the vulva.I, male, caudal bursa, ventral view.J, K, dissected tips of the spicules, J, right spicule, ventral view, K, left spicule, ventral view.L, spicules in situ, ventral view.M, female, posterior part, left lateral viewThe ridges are numbered from left to right, no.1-5 for the dorsal side, no.1'-7' for the ventral side.The arrows indicate the disappearance of the ridges.All the ridges are orientated as in Fig.5DAbbreviations: r, right side, v, ventral side Scales: A, I, M: 100 µm; B-H, J-L: 50 µm are close to the species described by Ortlepp (strong asymmetry of the lateroventral lobes of the caudal bursa, left ray 8 longer than the right one, gubernaculum not distinct), they are differentiated by the length of the left ala which is about half the body width and not two-thirds as in H. stellenboschius.In addition, right rays 3 and 4 on the one hand and left rays 4 and 5 on the other are joined except at their distal extremity.The association of these two latter characters of the caudal bursa is present only in Heligmonina bignonensis Diouf, Bâ & Durette-Desset, 1997, a parasite of Mastomys erythroleucus from Senegal which is the most closely related species by the body measurements and the pattern of the caudal bursa.Heligmonina bignonensis is differentiated by the more anterior position of the excretory pore, by the number of ventral cuticular ridges at mid-body (four versus five), by the left ala in the male being shorter than the body diameter, and by the length of left ray 6 being almost equal to that of ray 5 (approximately half the length of ray 5 in the specimens described above).We consider the specimens from Aethomys chrisophila as belonging to a new species which we have named Heligmonina boomkeri n. sp. in honour of our colleague, Prof. Joop Boomker.
REMARKSThe specimens mentioned above were registered in the Onderstepoort collections as "Heligmonina stellenboschius Ortlepp, 1939", a parasite of Myomys verroxii.Although the specimens from A. chrysophilus