Pterygodermatites (Mesopectines) quentini (Nematoda, Rictulariidae), a parasite of Praomys rostratus (Rodentia, Muridae) in Mali: scanning electron and light microscopy

Pterygodermatites (Mesopectines) quentini n. sp. (Nematoda, Rictulariidae) is described from the murine host Praomys rostratus in the south of the Republic of Mali. It differs from other species of the subgenus by the morphology of the head, which bears four simple cephalic papillae and a nearly axial oral opening, the number of caudal papillae, the number of precloacal cuticular formations, unequal spicules and the ratio of spicule lengths/body length. The use of scanning electron microscopy in combination with conventional light microscopy enabled us to give a detailed description of the morphological characters of this new species.


Introduction
Nematodes of the family Rictulariidae are divided into two genera, Rictularia Froelich, 1802 and Pterygodermatites Wedl, 1861 [9]. The buccal opening of the genus Rictularia is dorsally positioned and transverse with a single pharyngeal tooth, and the number of prevulvar armaments is lower than or equal to 34 pairs. In Pterygodermatites, the buccal opening is axial or slightly dorsal but never completely dorsal or transverse, with three pharyngeal teeth, and the number of prevulvar armaments ranges from 29 to 56 pairs. Based on different characters including the extent of the dorsal displacement of the buccal opening, the number of cephalic papillae and peribuccal denticles, arrangement of caudal papillae, and an increase in the number of prevulvar armaments, the species of Pterygodermatites are divided into five subgenera: Paucipectines Quentin, 1969, Neopaucipectines Quentin, 1969, Pterygodermatites Quentin, 1969, Mesopectines Quentin, 1969and Multipectines Quentin, 1969. The subgenus Mesopectines has been observed in some Palearctic rodents with two evolutionary lines, one in the Ethiopian realm and one in the Oriental realm. The Asian species of this subgenus differ from the African species by an increase in the number of prevulvar and postvulvar cuticular armaments. To our knowledge two subgenera, Neopaucipectines and Mesopectines, have been recorded in African Muridae [1,2,5,6,11]. In the present study we describe a new species of Pterygodermatites (Mesopectines) and report its occurrence in the murine rodent Praomys rostratus Miller, 1900.

Materials and methods
The nematodes studied herein were collected from P. rostratus captured in Piama in southeastern Mali, during a programme on the biodiversity in forest fragments of this area [7].
They were caught in February in riverine forest habitat. In total, 29 digestive tracts (21 males, 8 females) were examined under a stereo-microscope and helminth parasites were collected from the duodenum. They were fixed in 70% ethanol.
Nematodes were cleared in lactophenol and examined as wet mounts. Drawings were made with the aid of a drawing tube attached to a microscope. For scanning electron microscope studies, specimens were dehydrated in a graded ethanol series and dried using CO 2 in an Emitech K850 critical point dryer. After being mounted, specimens were coated with gold/palladium in a Quorum Technologies SC7640 sputter coater and examined with a Hitachi S-3400N scanning electron microscope at acceleration voltages between 3 and 20 kV.
Four males and three females were examined for morphological studies. Measurements are given in micrometers unless otherwise indicated. The first measurement is that of the holotype (for male) or allotype (for female), followed by the range of the paratypes in parentheses. Type specimens have been deposited in the Muséum National d'Histoire Naturelle (MNHN), Paris, France.  Prevalence and intensity: 13.7% (29 examined, 4 infected); 4.2 (2-9) worms per host.
Etymology: dedicated to Jean-Claude Quentin.
Description (Figures 1-3) Nematodes yellowish after fixation. Cephalic extremity with four simple cephalic papillae, two lateral amphids, six labial papillae in depressions (two ventral, two lateral at level of amphids and two dorsal) and circular oral opening with single crown of denticles ( Figures 1B and 2C). Buccal capsule shifted slightly dorsally with one dorsal and two ventral pharyngeal teeth ( Figure 1B). Cephalic protuberances present ( Figures  1B and 2C). Two subventral rows of cuticular armaments along body, plate-like, juxtaposed in anterior part of body and spinelike, scattered in posterior part ( Figures 1A, 2A Figure 1E). Tail 350 (300-350) long ( Figures 1F and 3G). Transverse cuticular striations absent in posterior third of body ( Figure 3F).

Discussion
Representatives of the subgenus Mesopectines parasitise rodents (Gerbillinae and Murinae), carnivores (Viverridae) and primates in both Africa and Asia [6,8]. They are characterised by a buccal opening that is apical in position or somewhat dorsally displaced, three pharyngeal teeth, a single crown of regular peribuccal denticles, 37-51 pairs of prevulvar cuticular armaments and two subventral rows of caudal papillae [4,10]. Our material conforms to this description. In the Ethiopian realm, five species have been described in this subgenus: P.  *According to Baylis (1928), the lengths of the female and the spicules are approximations. **According to Quentin (1969). ***According to Baylis (1928) (6), the pharyngeal teeth and the number of prevulvar armaments (Table 1). Pterygodermatites (M.) ortleppi and P. (M.) senegalensis possess spicules that are equal. Pterygodermatites (M.) taterilli, the species closest to our specimens, also has spicules of unequal length. However, our material differs from P. (M.) taterilli by the number of cephalic papillae and caudal papillae, the ratio of spicule lengths/body length and the number of precloacal formations (Table 1). In P. (M.) taterilli, all precloacal formations (4) are well developed, contrary to our specimens. Similar to our specimens, P. (M.) taterilli has cephalic protuberances but its buccal opening is dorsal. Pterygodermatites (M.) taterilli has been reported numerous times in gerbilline rodents in several countries (Burkina Faso, Côte d'Ivoire, Senegal) [8]. Based on the differences outlined above, however, we conclude that our material belongs to a new species. Moreover, contrary to the remaining species in the subgenus Mesopectines which have been found in rodents inhabiting the savanna biome, the new species parasitises a forest rodent species.