Tetrameres numida n . sp . ( Nematoda : Tetrameridae ) from Helmeted guineafowls , Numida meleagris ( Linnaeus , 1758 ) , in South Africa

Several Tetrameres species have been recorded from the African continent, of which Tetrameres fissispina (Diesing, 1861) Travassos, 1914 that parasitises ducks, pigeons and domestic chickens and Tetrameres americana Cram, 1927 that parasitises domestic chickens, turkeys and quails are the most commonly reported ones (Permin, Magwisha, Kassuku, Nansen, Bisgaard, Frandsen & Gibbons 1997; Poulsen, Permin, Hindsbo, Yelifari, Nansen & Bloch 2000).


INTRODUCTION
The genus Tetrameres Creplin, 1846 are cosmopolitan parasites, infecting a variety of aquatic and terrestrial avian hosts.Females are usually located in the proventricular glands, and the males are found free in the lumen of the proventriculus (Ander son 1992).
We here describe a new species of the genus Tetrameres from Helmeted guineafowls in South Africa for which we propose the name Tetrameres numida n. sp.
With regards to the classification of the genus Tetrameres we have followed that of Chabaud (1975), placing the genus into the subfamily Tetramerinae Railliet, 1915 within the family Tetrameridae Travassos, 1914, which is one of four families comprising the superfamily Habronematoidea.At the time the genus had been divided into the subgenera Tetrameres s. str., Gynaecophila Gubanov, 1950, Petrow i meres Chertkova, 1953and Gubernacules Rasheed, 1960. Chabaud (1975), arguing that this division could lead to errors and bore little phylogenetic significance, chose not to retain these, but divided the genus Tetrameres into the two subgenera Tetrameres (Tetrameres) Creplin, 1846 and Tetrameres (Micro tetrameres) Travassos, 1915.In the light of new findings, especially concerning the morphology of adults and larval stages of these two subspecies, Anderson (1992), while retaining their position within the subfamiliy, recognized Tetrameres Creplin, 1846 andMicrotetrameres Travassos, 1915 as two distinct genera, a generic classification that had been suggested by Skrjabin (1969).We adopt his view in the present paper.
Eight male Tetrameres sp. were recovered from the proventriculus, where they occurred free in the lumen and four females were dissected from the proventricular glands.Two guineafowls harboured a single male each, two hosts harboured two and three males respectively, and from a single host one male and four females were recovered.All hosts were mature guineafowls.The worms were fixed in 70 % ethanol and cleared in lactophenol for identification.All measurements, unless otherwise indicated, are in micrometres.

MALE:
Body elongated, tapering towards both ends, posteriorly to a tail with a short, pointed tip.Cuticle with fine transverse striation and longitudinal cuticular grooves.Total length 4.3-4.5 mm; maximum width 0.16-0.17mm.Inconspicuous lateral alae extending down the length of the body; parallell to these run two lateral rows of cuticular spines (Fig. 2F).One row of spines is situated dorsally, the second row ventrally to the lateral alae (Fig. 1B).A pair of deirids with apical spines is situated at approximately the height of the second pair of cuticular spines at a distance of 139-204 from the apex (Fig. 1B).Cuticular spines start at 93-154 from the apex, numbering approximately 42-47 per row.The nerve ring and excretory pore are 215-284 and 236-331 from the anterior extremity, respectively.The excretory pore is slightly posterior to the nerve ring.The triangular mouth is bounded by a pair of trilobed pseudolabia.The inner surface of each lobe carries two to four tooth-like processes.The precise number is difficult to assess in our specimens (Fig. 1A, 2A).Depth of buccal capsule 16-28, inner diameter 8-11.Oesophagus divided into muscular and glandular portion, 232-401 and 734-984, respectively.Total length of oesophagus 1 023-1 318.Spicules unequal and dissimilar.Right spicule tubular, with slight bend and spatulate tip, 106-170 long (Fig. 1C, 2D).Left spicule long and thin, trough-shaped, with spatulate tip.Shaft slightly twisted at 100-120 from proximal end.Total length 1 699-2 304 (Fig. 1D-F, 2C, 2E).A gubernaculum is absent.Tail length 257-297.Six pairs of caudal spines, three pairs each in two ventral and two lateral rows, respectively.One or two additional ventral spines may be present (Fig. 1C).FEMALE: Specimens in situ red.A minute head and tail of regular nematode shape, but often twisted or bent, emerge at opposite sides from the central part of the body which is distinctly globular and slightly bent along the axis (Fig. 1G-H, 3A, 3C).The cuticle bears marked transverse striation and four longitudinal cuticular grooves.The latter divide the body into four segments of which the two segments following the outer curve are slightly longer (Fig. 1G).Much of the internal detail is obscured by the egg-       The original reads 65-350 μm.We consider this a typing error and include the range of single measurements provided by Quentin & Barre (1976) b Skrjabin & Sobolev (1963) also include a description after Cram (1927), which differs slightly from that of Mamaev (1959) c Cremonte et al. (2001) give a range of 0.312-0.587mm

DISCUSSION
Some of the main morphological characteristics of many of the species belonging to the genus Tetrameres are listed in Table 2.
Of the Tetrameres species with two rows of cuticular spines, Tetrameres pattersoni Cram, 1933, T. paradisea and Tetrameres grusi Shumakovitsh, 1946 have only one spicule and the spicule measurements of the latter two species differ distinctly from those in our specimens (Ortlepp 1932;Schmidt 1962;Bush, Pence & Forrester 1973).
Tetrameres gubanovi Shigin, 1957 bears two rows of body spines, but has seven pairs of caudal papillae (Pence et al. 1975), as opposed to six pairs of caudal spines in T. numida n. sp.
The use of the term caudal spines or caudal papillae is not always clear.Pence et al. (1975) use the term caudal papillae for several species in their publication.They list T. paradisea as well as T. prozeskyi as having caudal papillae, but in the original descriptions Ortlepp (1932Ortlepp ( , 1964) ) clearly refers to cuticular spines.Thus, Pence et al. (1975) seem to use the term indiscriminately.Mawson (1968), however, describes T. nouveli as having caudal spines, but points out that in Tetrameres lobibycis Mawson, 1968 the spines are more like elongate papillae, and refers to Tetrameres calidris Mawson, 1968 and Tetrameres scolopacidis Mawson, 1968 as having papillae.
Tetrameres fissispina has been recorded from guineafowls in Africa (Fabiyi 1972;Vercruysse et al. 1985) and, like T. americana, has a high prevalence in domestic chickens, whose nematode fauna is similar to that of guineafowls (Mukaratirwa, Hove, Es mann, Hoj, Permin & Nansen 2001;Magwisha, Kassuku, Kyvsgaard & Permin 2002).Tetrameres fissispina distinguishes itself from the new species by its shorter spicules and the larger number of caudal spines.Tetrameres americana differs not only in the spicule size and the number and arrangement of caudal spines, but also in its four rows of somatic spines (Schmidt 1962;Gibbons, Jones & Khalil 1996).
The head of the female and the apical view of the head of the male of T. numida n. sp.most closely resemble Tetrameres tinamicola Pence, Mollhagen & Prestwood, 1975.The authors of the latter species describe the male head as possessing a triangular mouth surrounded by a pair of trilobed structures originating from the inner surface of the pseudolabia.Each lobe bears a pair of tooth-like processes in T. tinamicola.Similar processes can be seen in our specimens, but it is difficult to determine their exact number.However, there seem to be three or four per lobe.Pronounced lateral alae, as illustrated by Pence et al. (1975), were not found in our specimens.Moreover, T. tinamicola has a total of four rows of cuticular spines and the deirids are without apical spines.While the length of the left spicule of both species is similar, the right spicule of T. numida is only approximately half the length of T. tinamicola.Ortlepp (1932) described the buccal capsule of T. paradisea as having trilobed structures showing two to three bright refringent markings towards its posterior border.This, as well as other features of our specimens such as the transverse grooves anterior to the cloaca and the size of the spines, appeared so similar to T. paradisea that we initially considered assigning them to T. paradisea, especially in view of the fact that both were recovered from South African hosts.Close examination has nevertheless revealed distinct differences between the two.Tetrameres paradisea possesses a single spicule, whereas in our males two spicules are consistently present.While the arrangement of caudal spines is nearly identical and both carry three pairs of ventral and three pairs of externo-dorsal or lateral spines, the tail of T. paradisea is considerably shorter than that of our specimens (see Table 1).Ortlepp (1932) described and illustrated two rows of body spines found in T. paradisea and he uses this criterion to distinguish his species from Tetrameres nouveli which he lists as possessing four rows of spines.Cremonte, Digiani, Bala & Navone (2001) record T. paradisea as having four rows of spines, but cite Mollhagen (1976) as describing the dorsal rows of spines as very short, ending at 94-155 from the anterior end.
When comparing T. paradisea to T. prozeskyi, Ortlepp (1964) lists the length of the left spicule of the former species as 0.48 mm, but his original description of T. paradisea (Ortlepp, 1932) clearly states the length of the spicule as 0.69 mm.We list T. pro-zeskyi as monospicular, which differentiates it from our bispicular specimens.As regards T. prozeskyi it should be borne in mind that Ortlepp (1964) found a well-chitinized right spicule in three of the more than 30 males he examined.
In the summary of the description of Tetrameres cardinalis Quentin & Barre, 1976, the range of the length of the right spicule is given as 65-350 μm (Quentin & Barre 1976).As this seems erroneous, we decided to include the range provided in the same paper, namely 365-400, in Table 2. Similarly, we consider the first measurement these authors provide for the short spicule of T. paucispina as incorrect and believe it should read 120 instead of 12.
Apart from T. numida n. sp., only T. tinamicola and Tetrameres uxorius Mamaev, 1959 have a left spicule that reaches 2 mm in length, while in the remaining Tetrameres spp. the long spicule usually does not exceed 1 mm (Mamaev 1959;Pence et al. 1975).Relative to body length, however, there are other species with long spicules, such as T. lobibycis where the single spicule reaches about half of the body length (1.5 mm) and T. scolopacidis where the spicule length reaches almost two thirds of the body length (1.06-1.8mm) (Mawson 1968).
To our knowledge, Tetrameres phaenicopterus Ali, 1970 is the only member of the genus Tetrameres possessing a gubernaculum (Pence et al. 1975) and Tetrameres greeni Mawson, 1979 is unique in the genus Tetrameres in that it has caudal alae (Mawson 1979).Tetrameres spirospiculum Pinto & Vicente, 1995 is distinguished from our specimens and all the other species of Tetrameres by the spiral shaped distal end of the longer of its two spicules (Pinto & Vicente 1995).
The numbers of T. numida n. sp.recovered from the guineafowl hosts from Musina (Messina) were low, and the parasite was only found in the older birds, being absent in young adults.While it is possible that guineafowls are not the main host for this parasite, we attribute the low intensity of infection to the fact that the area had been experiencing a severe drought during the past years.This would decrease the survival rates of nematode eggs while at the same time causing the numbers of possible intermediate hosts necessary for the completion of the life-cycle to decline.While differences in the immune status between guineafowls of different age might play a role in the intensity of infection, we believe that the presence of T. numida n. sp. in older hosts simply reflects the increased possibility of prior exposure to the parasite as a function of time.

FIG. 3
FIG. 3 Tetrameres numida n. sp.Female.A. Three whole specimens, approximately 4 mm in length.Note the globular shape.B. Anterior extremity.C. Posterior end.Note the digested blood showing as dark smudge.D. Egg containing fully developed larva

d
Cremonte et al. (2001) quoteMollhagen (1976)  giving a range of 0.504-0.626mm e The length provided by Quentin & Barre (1976) is 12-154 μm.We consider this an error.Skrjabin & Sobolev give the width of the right spicule as 12 μm f According to Ortlepp (1964) in three of about 30 males a right spicule was present g Cremonte et al. (2001) quote Mollhagen (1976) as T. prozeskyi having varying caudal papillae (31:24 to 1:26 ratio between right and left spicule

TABLE 2 A
comparison of morphological characteristics of some species of the genus Tetrameres Creplin, 1846

TABLE 2
(cont.)nNo information at our disposal a