Lamotheoxyuris ackerti n . gen . , n . comb . ( Nematoda : Heteroxynematidae ) parasite of Neotoma spp . ( Rodentia : Muridae ) Lamotheoxyuris ackerti n . gen . , n . comb . ( Nematoda : Heteroxynematidae ) parásito de Neotoma spp . ( Rodentia : Muridae )

On the basis of the revision of the type material of Aspiculuris ackerti Kruidenier & Mehra, 1959, and new specimens collected from Neotoma nelsoni Goldman, 1905 (Rodentia: Cricetidae), in Veracruz, Mexico, we herein describe a new genus (Lamotheoxyuris n. gen.), to which A. ackerti is transferred as Lamotheoxyuris ackerti (Kruidener & Mehra, 1959) n. gen., n. comb. This new genus differs from all other genera included in Heteroxynematinae by the following main traits: 1) mouth surrounded by six lips; 2) extension of lateral alae reduced; and 3) lack of caudal alae.


INTRODUCTION
Aspiculuris ackerti Kruidenier & Mehra, 1959 was described as a parasite of Neotoma albigula Hartley, 1894 and Neotoma cinerea Ord, 1815 in Arizona (Kruidenier & Mehra 1959).Since then, the validity of its classification has been questioned several times.Hugot (1980) pointed out that A. ackerti does not possess the generic characteristics to support its placement in the genus Aspiculuris Schulz, 1924.In a re-description of A. ackerti, Miller & Schmidt (1982) found some discrepancies with respect to the original description, i.e., different number of caudal papillae and morphology of caudal alae.Finally, in agreement with Hugot (1980), Inglis et al. (1990) considered this nematode as species dubium.Based on the re-examination of type material of this nematode species and in new specimens collected in Veracruz, Mexico from Nelson's woodrat Neotoma nelsoni Goldman, 1905, we conclude that A. ackerti belongs to a new genus, which is herein described.
The type host of A. ackerti (N.albigula) is distributed from southeastern California and southeastern Utah to central Texas and from northeastern Michoacán to Hidalgo, Mexico (Macedo & Mares 1988).Other host of this nematode species, N. cinerea is found in mountainous areas from the southern Yukon and the westernmost Northwest Territories, south through British Columbia and western Alberta to northern California, Arizona and New Mexico, and as far east as the western portion of North Dakota (Smith 1997).Finally, N. nelsoni, which also hosts A. ackerti, is an endemic species of the Oriental Basin of Mexico.

METHODS
One specimen of N. nelsoni (Rodentia: Cricetidae) was trapped in the wild using standard methods approved by the American Society of Mammalogists (Gannon et al. 2007).This specimen was collected on 22 June 2007 from El Frijol Colorado, Municipality of Perote, in the state of Veracruz (19°34'20'' N,97°23'01'' W,2,435 masl) and examined for parasites.This locality is characterized by rocky hills with cactus pear, catclaw, agave and yucca.Intestinal nematodes were fixed in 70 % ethanol and cleared with lactophenol for morphometric study.For comparative purposes the following specimen from the U. S. National Parasite Collection (USNPC), Beltsville, Maryland, was examined: Aspiculuris ackerti Kruidener & Mehra, 1959 [USNPC 056163 (type specimens), 075506 and 088077].
Drawings and measurements were made with a Zeiss microscope equipped with a drawing tube.For scanning electron microscopy (SEM) study, nematodes were dehydrated in graded series ethyl alcohol dilutions and critical-point dried with carbon dioxide.Specimens were coated with a gold-palladium mixture and examined in a Hitachi S-2460N scanning electron microscope at 15 kV.Range is followed by the mean and standard deviation; sample size (n) is provided in parentheses.The host was obtained under the collecting permit FAUT-0002 issued to Fernando Cervantes Reza and is housed at the Museum of Natural Science (Louisiana State University) as specimen number LSUMZ 36663.Voucher specimens of parasites were deposited in the Colección Nacional de Helmintos (CNHE), Instituto de Biología, Universidad Nacional Autónoma de México, Mexico City.

Description of the genus
Lamotheoxyuris n. gen.
Diagnosis: Oxyurida, Heteroxinematidae, Heteroxynematinae.The worms are small in size.Males are shorter than females.Cephalic vesicle present; cervical alae present, extending from the cephalic region to the midbody in males and before the vulva in females; each cervical alae have two crests (sensu Hugot 1980) in cross section.Lateral alae are reduced in the both sexes.A ventral ala is present in males, beginning at the mid-body region and ending before the cloaca.The mouth is surrounded by six lips, one pair of lateral "epaulettes" with two amphids and four labial papillae.Males without caudal alae.Gubernaculum and spicules are absent.Ten caudal papillae are arranged as follows: one pair precloacal, one pair adcloacal, a single median postcloacal papilla closely associated with the cloaca, one posterior pair followed by one single median papilla, and one additional posterior pair.
Other records: ex N. cinerea from Colorado and Wyoming.N. albigula from New Mexico, and N. nelsoni from Veracruz, Mexico.
Etymology: The genus is named after Dr. Marcos Rafael Lamothe-Argumedo in commemoration of his 50 th anniversary as a scientific researcher in Helminthology.

Remarks
Following Petter & Quentin (1976), our specimens are included in Heteroxynematidae: Heteroxynematinae because the last pair of male postcloacal papillae is isolated near the caudal extremity, the glandular portion of the ovijector is never in the form of an enlarged ring at the distal end of the muscular vagina vera, eggs lacking operculum, and the pharyngeal and buccal structures are simples.To date, Heteroxynematinae comprises 10 genera distributed worldwide (Erkulov 1975, Petter & Quentin 1976, Mas-Coma & Esteban 1982).Two of these 10 genera can be distinguished from the new genus because they are parasites of birds: Eudromoxyura Anderson & Prestwood, 1972 and Syphaciella Mönnig, 1924, while Lamotheoxyuris infects rodents; in addition, Eudromoxyura has an intestinal caecum behind the esophageal bulb, which is absent in Lamotheoxyuris, and three well developed trilobed lips with small interlabia (vs.six lips without interlabia in the new genus) (Anderson & Prestwood 1972); likewise, the presence of triangular teeth in the vestibule as well as gubernaculum, spicules, and caudal alae allow to differentiate Syphaciella from Lamotheoxyuris, which lacks these structures (Petter & Quentin 1976).
The other eight genera included in Heteroxynematinae (Aspiculuris Schulz, 1924;Dermatopallarya Skrjabin, 1924;Dentostomella Schulz & Krepkogorskaja, 1932;Fastigiuris Babaev, 1966;Heteroxynema Hall, 1916;Ivaschkinonema Erkulov, 1975;Kahmannia Mas-Coma & Esteban, 1982, & Rauschoxyuris Quentin, 1975) parasitize mammals, as does the new genus.However, two of them (Dentostomella and Kahmannia) lack cervical alae (present in Lamotheoxyuris), and have esophageal teeth and a single spicule (both characteristics absent in the new genus) (Petter & Quentin 1976, Skrjabin 1982, Mas-Coma & Esteban 1982).The species included in the remaining six genera that parasitize mammals have cervical alae like Lamotheoxyuris ackerti.However, the new genus differs from all these genera by the following main characteristics: Dermatopallarya have three lips and a defined buccal cavity instead of six lips and a mouth opening directly to the esophagus, as in the new genus; in addition, males of Dermatopallarya possess two ventral cuticular swellings, which are absent in the new genus (Petter & Quentin 1976, Skrjabin 1982); the esophageal bulb in Fastigiuris is reduced or absent whereas this structure is well developed in the new genus; also, the cervical alae in Fastigiuris are markedly bent in the ventral region (Petter & Quentin 1976) while the cervical alae are straight in the specimens described in this study.Likewise, Lamotheoxyuris can be differentiated from Heteroxynema because males of this later genus have a precloacal pseudosucker, gubernaculum, and a spicule (Petter & Quentin 1976, Hugot & Sutton 1989), which are all lacking in the new genus.Ivaschkinonema possesses four differentiated lips and caudal rings (Erkulov 1975), whereas Lamotheoxyuris has six lips and lacks caudal rings.Finally, Rauschoxyuris has a precloacal denticulate crest (Quentin 1975), that is absent in the new genus.
The new genus most closely resembles to Aspiculuris.Nevertheless, both genera can be distinguished based on the following traits: 1) Aspiculuris has caudal alae (absent in Lamotheoxyuris); 2) lateral alae in Aspiculuris run along the body, while the lateral alae only reach the mid-body region in the new genus; 3) cervical alae in Aspiculuris narrow posteriorly to give a spearhead-like or an arrowhead-like outline to the cephalic end, differentiating it from lateral alae; in Lamotheoxyuris, the cervical alae are continuous with the lateral alae, with no superficial distinction; 4) cross sections of cervical and lateral alae in our material, showed the same morphology, being constituted by two crests along its extension; in Aspiculuris spp., cross sections of cervical alae showed two crests, while the lateral alae had only one crest [for examples, see Figs. 1C, 1D, and 1E for Aspiculuris tetraptera (Nitzsch, 1821), and Figs. 3J, 3K, 3L, and 3M for Aspiculuris africana Quentin, 1966in Hugot (1980); finally, 5) the mouth in Aspiculuris is surrounded by three undivided lips, while L. ackerti possesses six lips that are clearly differentiated by SEM.Observations of the anterior end of A. ackerti in face view, made by Miller & Schmidt (1982) with light microscopy, could not establish the true number of lips.