Search

As part of an ongoing project to inventory the helminth parasites of amphibians from the state of Hidalgo, Central Mexico, specimens of Rhinella horribilis were collected from three municipalities: Eloxochitlán, Huehuetla, and San Felipe Orizatlán. A total of eight taxa of helminths were found: three digeneans (Haematoloechus sp., Langeronia macrocirra, and Mesocoelium danforthi) and five nematodes (Cosmocerca sp., Cruzia morleyi, Ochoterenella chiapensis, Oswaldocruzia subauricularis, and Rhabdias sp.). The highest species richness was recorded in Huehuetla. All reports of these species of helminths represent new locality records for Mexico.

The Mexican free-tailed bat ( Tadarida brasiliensis ) is an abundant, widely distributed species in Mexico, except for most of the Yucatan peninsula. We studied the helminth fauna of T. b. mexicana at seven localities in the State of Zacatecas in order to advance the knowledge of helminth parasites of wild vertebrates in northern-central Mexico. Eighty-four bat specimens were examined for the presence of helminth parasites following standard procedures; helminths found were identified and infections were characterized. Of the specimens examined, 65.47 % were parasitized. The helminth fauna comprises five taxa: three digeneans ( Dicrocoelium rileyi , Ochoterenatrema labda , and Urotrema scabridum ); one cestode ( Vampirolepis sp.); and one nematode ( Tadaridanema delicatus ). We present a brief morphological description of Urotrema scabridum . D. rileyi was the most prevalent and abundant helminth species. The intestine was the habitat most parasitized, with four species. Indirect life cycles predominate, and are related to the insectivorous habits of this host. Further studies on this host-parasite system are necessary to contribute to population monitoring and conservation; biogeographic patterns of helminth parasites of bats should also be studied to explore their origins and evolution in the region. U. scabridum is reported for the first time from Zacatecas. All species are new locality records.

The helminth community of Lithobates spectabilis (n =77) was studied from Las Pilas (low altitude) and Metznoxtla (high altitude), Biosphere Reserve Barranca de Metztitlán, Hidalgo, Mexico. Species diversity was compared at the infracommunity and the component community level using Hill numbers, and the beta diversity was calculated. Five species of Digenea, 5 of Nematoda, and 2 of Acanthocephala were found in the frogs from the 2 localities. The species richness of parasites in Las Pilas (9 species) was higher than that of Metznoxtla (7 species). The helminth community in Las Pilas was dominated by nematodes and, in Metznoxtla, it was dominated by digeneans. The most prevalent species in Las Pilas was Foleyellides cf. flexicauda (65% of frogs were infected) and, in Metznoxtla, it was Megalodiscus americanus (76% were infected). Glypthelmins quieta was the species with the highest mean abundance in both localities (Las Pilas = 4.5; Metznoxtla = 11.0). The difference in species composition between the 2 localities was significant (Anosim; R = 0.54, p < 0.05). The differences in the composition of species of helminths between the 2 localities suggest that local environmental conditions are different, which may reflect differences in local host diet.

We present an updated checklist of helminth species infecting cricetid and heteromyid rodents (Rodentia: Cricetidae and Heteromyidae) distributed in Mexico. For each helminth record, we include information on helminth taxonomy, location within the host, life stage, host associations, collection localities, citation, and museum collections, when available. We recorded more than 73 helminth species from 47 host species distributed across 21 states in Mexico. The present list represents the most up-to-date knowledge of helminth species infecting cricetid and heteromyid rodents in Mexico.

As a part of an ongoing project to inventory the helminth parasites of rodents in Mexico, 30 individuals of Aspiculuris americana were collected inhabiting the intestine from three specimens of the rock mouse Peromyscus difficilis, collected from Cerro Xihuingo, Municipality of Tepeapulco, Hidalgo State, Mexico. This species of nematode parasite different species of the genus Peromyscus (P. gossypinus, P. leucopus, P. maniculatus, and P. floridanus) distributed from Yukon Territory in Canada to Florida in the United States of America. This is the first report of Aspiculuris americana in a Mexican endemic rodent, widening the known distribution of the species to the southern portion of the country.

Salamanders of the tribe Bolitoglossini Hallowell are a highly diversified group of amphibians, and their helminth parasite fauna has been scarcely studied. Some species of plethodontid salamanders distributed along the Trans-Mexican Volcanic Belt, in central Mexico, were sampled, and their helminth parasites were recovered for taxonomic identification. Specimens of a pharyngodonid nematode from 2 species of bolitoglossines of the genus Pseudoeurycea Taylor were morphologically identified as Batracholandros salamandrae (Schad, 1960) Petter and Quentin, 1976. These specimens were studied in further detail through light and scanning electron microscopy and were sequenced for 2 ribosomal genes and 1 mitochondrial gene to test the hypothesis of whether B. salamandrae is a species widely distributed in salamanders across the Nearctic biogeographic region, or if it represents a cryptic species complex. Our molecular results revealed that these specimens consisted of 2 genetic lineages in concordance with host species, although with slight morphological differences among specimens in each of them. A thorough study, including the generation of molecular data from individuals from other areas of North America, and the examination of type specimens, is required to test the reliability of these morphological differences and to corroborate the species identity of the 2 genetic lineages.

Trichuris guanacastei n sp., a parasite isolated from the Salvin’ spiny mouse Heteromys salvini, collected from the Guanacaste Conservation Area, Costa Rica, during February 1996 is described. The new species was compared morphologically with the 29 known species that parasitize rodents distributed in 12 families in North and South America; T. guanacastei n. sp. it is characterized by the following set of traits: presence of a spicular tube (measuring 0.72-0.99); thick proximal cloacal tube and a short distal cloacal tube with a total length of 0.72-1.36; eggs 0.03-0.05 long and a semi-protrusible vulva. The new species represents the first one described in the genus in Costa Rica and the fifth one described in the Americas that parasite Heteromyidae. Resumo O objetivo deste estudo foi descrever Trichuris guanacastei n. sp., um parasita isolado do rato espinhoso de Salvin, Heteromys salvini, coletado na Área de Conservação de Guanacaste, Costa Rica, durante fevereiro de 1996. A nova espécie foi comparada morfologicamente a 29 espécies conhecidas que parasitam roedores, distribuídas em 12 famílias na América do Norte e do Sul. T. guanacastei n. sp. é caracterizado pelo seguinte conjunto de características: presença de um tubo espicular (que mede 0.72-0.99); tubo proximal cloacal e um tubo distal cloacal com uma longitude total de 0.72-1.36; ovos de 0.03-0.05 de largura e uma vulva semi-protrusible. A nova espécie representa a primeira descrita do gênero na Costa Rica e a quinta descrita nas Américas que parasita Heteromyidae.

Fifty-five adult Dicrocoelium rileyiMacy, 1931 parasitizing Tadarida brasiliensis (Geoffroy, 1824) from Durango, Nuevo Leon, Puebla, Zacatecas and Mexico State were morphologically described and morphometrically analyzed. To evaluate the degree of variation among populations from the five localities, 27 morphometric measures of this species were transformed into an orthogonal factor by principal component analysis (PCA), and a posterior comparison among populations was performed using discriminant analysis of principal components (DAPC). Significant differences were observed with exceptions between the Puebla – Zacatecas and Nuevo Leon – Mexico State populations when forming three groups with an 88 % assignation. The Durango population was the most dissimilar population. These results show that the morphological traits of D. rileyi are variable among the populations in this study due to local intraspecific variation; however, some of the specimens present in the distinct localities may represent different species. Molecular analysis is necessary to accurately define whether the populations involved in our study constitute one or several species.

Eighty-six specimens representing 7 species of rodents from 9 localities in the state Zacatecas were examined for helminths. Only 5 host species were found to harbor at least 1 species: Chaetodipus sp., Dipodomys merriami atronasus, Neotoma mexicana, Otospermophilus variegatus, and Peromyscus sp.; in contrast Mus musculus and Reithrodontomys sp., were not parasitized. Three species of cestodes (Catenotaeniidae gen. sp., Hymenolepis sp., and Raillietina sp.) and 7 nematodes (Gongylonema sp., Heteromyoxyuris longejector, Lamotheoxyuris cf. ackerti, Mastophorus dipodomis, Rauschtineria sp., Pterygodermatites dipodomis, and Trichuris dipodomis) were recorded. The intestine is the most parasitized (7 taxa) and trematodes were not found. The highest species richness was recorded in D. merriami atronasus from Rancho La Barranca (6 taxa), which also had the most sampling effort. H. longejector in Chaetodipus sp. from El Gordillo, showed the greatest mean abundance, and mean intensity values, followed by Rauschtineria sp. in O. variegatus from Morelos-Zacatecas Road. All species are new locality records, 14 new host records, and 2 taxa recorded for the first time in Mexico: Rauschtineria sp. and M. dipodomis. This is the first study of helminth parasites of rodents from Zacatecas.

We document parasitation of a wild cougar (Puma concolor) by the nematode Lagochilascaris minor in Hidalgo State, Mexico. This finding contributes to our understanding of the epidemiology of this zoonotic agent in Mexico.

Aplectana uaehi n. sp., which inhabits the small intestine of Ambystoma velasci, the Plateau Tiger Salamander, collected from Lago de Tecocomulco, Hidalgo, Mexico, is described. This new species is distinguished from all other species of Aplectana in having 3 toothlike projections in the esophagus, each tooth bearing 3 ridges. The new species most closely resembles Aplectana hylambatis. The latter species also has 3 toothlike projections, but they are covered by a thick cuticle and each has a small cuticular spike that projects into the buccal cavity (Baker, 1980), features not present in members of Aplectana uaehi n. sp. In addition, the 2 species differ in the length of the spicules of males (240–350 µm vs. 320–520 µm, respectively) and the number of postcloacal papillae (4–6 pairs vs. 10 pairs, respectively). This record represents the first report of Aplectana in a member of the Order Caudata and is the first member of the genus found as a parasite of a species endemic to Mexico that is itse...

As a part of an ongoing project to inventory the helminth parasites of rodents in Mexico, 85 specimens of 2 families of rodents were collected from the Mexican Plateau: Cricetidae ( Neotoma sp., Neotoma leucodon , Onychomys arenicola , Peromyscus sp., Peromyscus eremicus , and Reithrodontomys sp.) and Heteromyidae ( Chaetodipus sp., Chaetodipus eremicus , Chaetodipus hispidus , Dipodomys merriami , Dipodomys ordii , Dipodomys ornatus, Dipodomys spectabilis , Liomys irroratus , Perognathus sp., and Perognathus flavus ). A total of 13 taxa of helminths were found: Heteromyoxyuris longejector, Heteromyoxyuris otomii, Heteromyoxyuris sp., Onchocercidae gen. sp. 1 and sp. 2, Physalopteridae gen. sp., Protospirura dipodomis, Pterygodermatites dipodomis, Subulura sp., Syphacia sp., Trichuris dipodomis, Vexillata liomyos, and Vexillata armande. The highest species richness was recorded in D. merriami (7 taxa). This study is the first report of nematodes from O. arenicola (Physalopteridae gen. sp.) and C. eremicus (H. longejector) and for V. liomyos from D. merriami . All reports of these species of nematodes represent new collection localities in Mexico.

As a part of an ongoing project in order to inventory the helminth parasites of rodents in Mexico, 49 individuals of Syphacia (Seuratoxyuris) peromysci were collected from five specimens of the Rock Mouse Peromyscus difficilis caught in Veracruz state, Mexico. This is the first report of S. peromysci in a Mexican endemic rodent, widening the known distribution of the species to the southern portion of the country.

Species distribution modelling has been a powerful tool to explore the potential distribution of parasites in wildlife, being the basis of studies on biogeography.Vexillataspp. are intestinal nematodes found in several species of mammalian hosts, such as rodents (Geomyoidea) and hares (Leporidae) in the Nearctic and northern Neotropical regions. In the present study, we modelled the potential distribution ofVexillataspp. and their hosts, using exclusively species from the Geomyidae and Heteromyidae families, in order to identify their distributional patterns. Bioclimatic and topographic variables were used to identify and predict suitable habitats forVexillataand its hosts. Using these models, we identified that temperature seasonality is a significant environmental factor that influences the distribution of the parasite genus and its host. In particular, the geographical distribution is estimated to be larger than that predicted for its hosts. This suggests that the nematode has the potential to extend its geographical range and also its spectrum of host species. Increasing sample size and geographical coverage will contribute to recommendations for conservation of this host–parasite system.

Heteromyoxyuris otomii n. sp., which inhabits the intestinal caecum of Perognathus flavus (Heteromyidae), in Zaragoza, Hidalgo, Mexico, is described. This new species differs from the 2 other congeneric species in the morphology and length of lateral alae in males. Heteromyoxyuris deserti has simple lateral alae located at both sides of the body, whereas in the new species, these structures are double at both sides; in contrast, lateral alae of Heteromyoxyuris longejector begin at the posterior half of the body, whereas they arise in the first third in the new species. Heteromyoxyuris longejector was found in 2 new host species, i.e., Perognathus amplus and Chaetodipus hispidus. This record represents the first record for the species in Mexico, increasing its geographic distribution.

Vexillata geomyos n. sp. is described as a parasite of Attwater's pocket gopher, Geomys attwateri (Geomyidae), from Welder Wildlife Refuge, Texas. The new species possesses 12 cuticular ridges; based on this character, it can be distinguished from 7 of the 13 species in the genus. From the 6 remaining species, V. geomyos can be differentiated because the dorsal ray in 3 of them (V. armandae, V. dessetae, and V. vexillata) has 2 short branches arising from main trunk, whereas dorsal ray of the new species lacks these branches. In addition, V. geomyos can be distinguished from V. brooksi because its spicules are divided at the tip (whereas in the new species, spicules are whole). The new species differs from V. legallae and V. convoluta in the number and arrangement of cuticular ridges at the posterior region of the body.

Eight species of fleas were collected from several mammal species in northern and central Mexico. Four species extend the distribution and three present new state records. Mammal hosts species comprise rodents in most cases and one mustelid, from the states of Durango and Queretaro.

Individuals of a new species of Vexillata were collected from the small intestines of Liomys pictus from the Estaci6n de Biología Chamela, in Jalisco State, Mexico. The new species shows an array of characters that allow us to recognize it as a member of Vexillata; however, it can be distinguished from other species of the genus in that males possess an asymmetrical caudal bursa, females possess a characteristic cuticular inflation at the level of the ovijector, and both sexes possess a synlophe with 9 ridges at the midbody. Additional detail of the synlophe of Vexillata armandae Gardner et al., 1994 from Chaetodipus hispidus in New Mexico shows that both sexes have 12 cuticular ridges just posterior to the cephalic inflation, and in the posterior region of the body, females have 9 ridges of equal size while males possess 11 equal-sized ridges. In both sexes, the carene disappears at the posterior end of the body.

Caballerolecythus ibunamin. gen., n. sp. is described from the intestine of 2 species of rodents ( Liomys irroratus (Gray, 1868) and Peromyscus difficilis(Allen, 1891)) from Pinonal, El Carmen Tequexquitla, Tlaxcala state, Mexico. These specimens represent a new genus and a new species of Dicrocoeliinae by possession of an extremely short ceca (ending at equatorial level of ovary); vitelline follicles that begin posterior to these structures, without overlapping; and a body that is long and slender (length/width ratio 1:17-21). To the best of our knowledge, this combination of characters has not been reported in other genera of this subfamily (Athesmia Looss, 1899; Unilaterilecithum Oshmarin in Skrjabin and Evranova, 1952; and Pseu- dathesmia Travassos, 1942).

The helminth parasite fauna of the hylid frog Pseudacris hypochondriaca in several localities along the Baja California Peninsula in northwestern Mexico is presented. The helminth fauna consists of 4 species of nematodes (Oswaldocruzia pipiens, a larval form of an Ascaridid, 2 new species belonging to the genera Rhabdias and Cosmocercoides), and 1 species of digenean (Gorgoderina sp.). The new species of Rhabdias represents the 88th species assigned to the genus and the third species described from Mexican anurans. Also, the species of Cosmocercoides represents the 20th species assigned to the genus and the first representative of this genus described from Mexico.

RESUMEN. La Cuenca Oriental se ubica en los estados de Puebla, Tlaxcala y Veracruz, localizada en el Eje Volcanico Transmexicano; hasta la fecha, solo se han registrado en la localidad dos especies de helmintos ( Caballerolecythus ibunami y Lamotheoxyuris ackerti ) y tres sifonapteros ( Anomiopsyllus perotensis , Stenistomera alpina y Echidnophaga gallinacea ). Para el presente trabajo se realizaron dos muestreos, en junio de 2007 y julio de 2008, los cuales incluyeron cinco localidades de la region, colec-tandose ocho taxa de helmintos y nueve de pulgas, todos provenientes de Liomys irroratus , Dipodomys phillipsii , Peromyscus difficilis , P. maniculatus y Reithrodontomys megalotis . Se registran nuevos hos-pederos y localidades para Mexico en siete taxa de helmintos y solo uno para las pulgas. Palabras clave: Helmintos, Sifonapteros, Cuenca Oriental, Liomys irroratus , Dipodomys phillipsii , Pe­romyscus difficilis , P. maniculatus , Reithrodontomys megalotis . Falcon-Ordaz, J., R. Acosta, J. A. Fernandez & G. Lira-Guerrero.

Como parte de un estudio sobre los metazoarios parásitos de mamíferos de México se recolectaron 4 ejemplares de ratones tlacuache: 2 de Tlacuatzin canescens (Allen, 1893) procedentes de Oaxaca y 2 de Marmosa mexicana Merriam, 1897 de Veracruz. Se presentan 5 registros nuevos de hospedero y localidad para ácaros de las especies Ixodes luciae Sénevet, 1940, Ixodes sinaloa Kohls y Clifford, 1966, las pulgas Plusaetis mathesoni (Traub 1950) y Polygenis martinezbaezi Vargas 1951, así como para el cestodo Hymenolepis sp. y por primera vez en México se registra el nematodo Hoineffia simplicispicula Navone, Suriano y Pujol, 1991.

Helmintos, Sifonápteros, Cuenca Oriental, Liomys irroratus, Dipodomys phillipsii, Peromyscus difficilis, P. maniculatus, Reithrodontomys megalotis.

Se llevó a cabo un análisis panbiogeográfico, a partir de un análisis de parsimonia de endemismos (PAE) de las especies de helmintos parásitos intestinales del género Vexillata (Nematoda: Ornithostrongylidae) y sus especies de huéspedes, mamíferos de las familias Geomyidae y Heteromyidae. Se realizaron dos análisis, el primero empleando solo aquellas especies del género Vexillata con más de dos localidades, y el segundo, analizando todas las localidades de este género de parásito en unsolo trazo individual. Se obtuvieron tres trazos generalizados a partir del PAE del primer análisis: costa norte de Venezuela, América Central y Neártico. Solo uno de los trazos fue sustentado por una especie de parásito y su huésped (V. tejerai y Heteromys anomalus). Se propone la existencia de un nodo biogeográficoen Colombia, entre el trazo de la costa norte de Venezuela y el de América Central en el noroeste de Colombia, en los límites con Panamá; y otro en la zona central de México. Estos trazos y nodos coinciden con algunos propuestos por otros autores. En general se observa que estos sistemas pueden ser explicados como tres componentes bióticos. En particular el de América del Sur puede corresponder con aquellas que especiaron por aislamiento (V. scorzai), y especies con distribuciones amplias (V. tejerai), quizá más relacionadas a etapas de movilidad de sus huéspedes (Heteromys).

Aspiculuris huascaensis n. sp. was found in the intestine of Mus musculus collected from 2 localities in Hidalgo, Mexico, and is described herein. The new species possesses cervical alae abruptly interrupted at mid-length of esophageal bulb form an acute angle, distinguishing it from 5 of the 17 species in the genus. The new species is differentiated from 11 of the remaining species by having cervical alae that form an acute angle and end at mid-length of the esophageal bulb. Aspiculuris huascaensis n. sp. most closely resembles A. tetraptera in the position of the terminal end of the cervical alae. However, the new species can be distinguished from that species by the number of caudal papillae (12 vs. 14), the presence of a sessile precloacal papilla between 2 cuticular folds, and by having a single pedunculate papilla located slightly posterior to the cloaca.

Aspiculuris huascaensis n. sp., Mus musculus, Mexico, Hidalgo.

The present study analyses the taxonomic status of eleven species of trichostrongylins that parasitize rodents and lagomorphs deposited in the Colección Nacional de Helmintos, Instituto de Biología. UNAM. Mexico. This analysis is based on the morphology of the synlophe, characteristic that had not been studied for most of these nematode species and at present, it has a very important taxonomic value. As a result of this study, the identity of five species is ratified (Trichostrongylus calcaratus, Obeliscoides cuniculi, Carolinensis huehuetlana. Stilestrongylus peromysci and Nippostrongylus brasiliensis), the transference suggested previously for two more (Vexillata convoluta and Vexillata vexillata) is confirmed, Trichostrongylus chiapensis is synonymized with Boehmiella willsoni, and finally Lamothiella romerolagi is re-determined as Teporingonema cerropeladoensis and Stilestrongylus atlatilpinensis as Stilestrongylus hidalguensis.

On the basis of the revision of the type material of Anoplostrongylus delicatus Schwartz, 1927, and new specimens collected from Tadarida brasiliensis mexicana (Saussure, 1860) in 4 arid localities from Mexico, we describe a new genus (Tadaridanema n. gen.), to which A. delicatus is transferred (as Tadaridanema delicatus (Schwartz, 1927) n. gen., n. comb.). This new genus differs from all other genera included in Anoplostrongylinae by having ray 2 larger than ray 3. In addition, T. delicatus can be differentiated from the type species of Anoplostrongylus (Anoplostrongylus paradoxus (Travassos, 1918)) because it possess vestibular branches equal in length, cephalic inflation divided into 2 regions, and synlophe with many small ridges at the midbody level, whereas in T. delicatus, vestibular branches are equal in size, cephalic inflation is simple in structure, and the synlophe has only 2 well-developed dorsal cuticular ridges.

Sciurodendrium bravohollisae n. sp. (Heligmonellidae) is described as an intestinal parasite of 2 squirrels, Sciurus aureogaster Cuvier, 1829, collected from Los Robles, Municipio de Tlalnepantla, Morelos State, Mexico. The new species differs from all other congeners in possessing a very well-developed and sacciform genital cone. This is the seventh species described for the genus and the first one recorded in Mexico.

In July 1999, 2 heteromyid rodents Heteromys desmarestianus Gray, 1868, were collected from the Area de Conservacion Guanacaste, Costa Rica, and examined for parasites. Individuals of a new species of Vexillata (Travassos, 1937) Durette-Desset, 1970, were found from the intestine of hosts. Vexillata brooksi n. sp. differs from all other congeners by the presence of spicules divided at the tip instead of simple spicules. The new species closely resembles Vexillata legallae Denke, 1977, and Vexillata convoluta (Caballero and Cerecero, 1943); however, it can be distinguished from both species by possessing a smaller number of cuticular ridges at the posterior part of the body in males (9 vs. 11 and 12, respectively) and by the absence of a carene at this level.

The phylogenetic relationships of 14 species of Stilestrongylus were analyzed using the comparative morphology of 21 characters. We obtained 2 shortest trees of 50 steps, with a consistency index of 0.540 and 25 apomorphic character states. Ingroup monophyly was supported on these trees by 2 and 3 synapomorphies, respectively, and the ingroup was defined by the following characters: greater number of ventral ridges relative to the number of ridges dorsally, asymmetric bursa, and externodorsal rays differing in size. Sister-group relationships among Stilestrongylus and the other genera designated as outgroups are relatively consistent with those postulated by Durette-Desset's in a classification of the Nippostrongylinae. The ancestor of the species groups comprising Hassalstrongylus, Guerrerostrongylus, and Stilestrongylus originated and diversified in murids in the Neotropical region. Species of Hassalstrongylus occur in rodents between southeastern North America and the eastern part of South America (Brazil and Argentina), whereas species of Guerrerostrongylus and Stilestrongylus diversified exclusively in rodents in the Neotropics.

In the present work, a total of 339 nominal taxa of helminths (53 trematodes, 46 cestodes, 12 acanthocephalans, 227 nem-atodes, and 1 hirudinean), associated with 136 taxa of wild mammals from Mexico, are listed. Information on hosts, hab-itat, distribution, and records is included; these data come from 242 localities, pertaining to 31 of the 32 Mexican states,and represent the current knowledge on helminth parasites of wild mammals in Mexico. Eighteen taxa of helminths are registered for the first time in Mexico, and 46 new locality records are presented.

Plethodontid salamanders represent a group of amphibians that show a great evolutionary diversification in México, however no study of their helminth parasites had been conducted thus far. In this paper, we describe Cosmocerca acanthurum n. sp. (Nematoda: Cosmocercidae) from the intestine of the plethodontid salamanders Pseudoeurycea leprosa and Chiropterotriton orculus from Llano Grande and Texcalyacac, Estado de México, in Central México. Cosmocerca acanthurum n. sp. is easily distinguished from all other species of Cosmocerca in that females possess a uniquely spined tail, a character no seen in congeners. In addition, we compiled all the information of helminth parasites of plethodontid salamanders, and we present it in the form of a checklist of both parasite-host, and host-parasite. A brief analysis of the helminth parasite species composition is presented regarding life-history and development characteristics of plethodontids.

"A new species of Angiostoma (Angiostomatidae) is described from the intestine of the plethodontid salamander, Pseudoeurycea mixteca from Puebla State, in central Mexico. The new species closely resembles Angiostoma limancis, Angiostoma kimmeriensis, Angiostoma spiridonovi, Angiostoma stammeri, and Angiostoma carettae, because they all possess 8 pairs of pedunculate papillae in the caudal region; however, the new species can be distinguished by the unique arrangement of papillae, with 1 pre-cloacal pair, and 7 post-cloacal pairs. Among the 12 congeneric species of Angiostoma described so far, 2 have been described as parasites of salamanders, Angiostoma plethodontis from Plethodon cinereus and Plethodon richmondi in Virginia, USA, and Angiostoma onychodactyla from Onychodactylus japonicus in Japan. Angiostoma lamotheargumedoi n. sp. is readily distinguished from these 2 species by the presence of lateral alae and by the number of pre-cloacal papillae."

As a part of an ongoing inventory of the helminth parasites of freshwater fishes in Mexico, 676 specimens were collected between November 2007 and December 2008 in 23 localities along the upper Mezquital River Basin in Durango State, northern Mexico. Sixteen species of hosts, mostly corresponding to Nearctic freshwater elements, were studied. A total of 1,230 individual worms were collected during this survey, representing 25 species of endohelminths of which 9 were digeneans, 3 were cestodes, 4 were acanthocephalans, and 9 were nematodes. The checklist contains 24 new hosts and 42 new locality records. The information provided in this checklist may be helpful for our understanding of the biodiversity and historical biogeography of this host-parasite system, since the Mezquital River Basin mostly contains a Nearctic freshwater fish fauna, with a few Neotropical and endemic elements and may represent a transitional area from a biogeographical point of view.