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Helminth species of Neotropical bats are poorly known. In Mexico, few studies have been conducted on helminths of bats, especially in regions such as the Yucatan Peninsula where Chiroptera is the mammalian order with the greatest number of species. In this study, we characterized morphologically and molecularly the helminth species of bats and explored their infection levels and parasite–host interactions in the Yucatan Peninsula, Mexico. One hundred and sixty-three bats (representing 21 species) were captured between 2017 and 2022 in 15 sites throughout the Yucatan Peninsula. Conventional morphological techniques and molecular tools were used with the 28S gene to identify the collected helminths. Host–parasite network analyses were carried out to explore interactions by focusing on the level of host species. Helminths were found in 44 (26.9%) bats of 12 species. Twenty helminth taxa were recorded (7 trematodes, 3 cestodes and 10 nematodes), including 4 new host records for the Americas. Prevalence and mean intensity of infection values ranged from 7.1 to 100% and from 1 to 56, respectively. Molecular analyses confirmed the identity of some helminths at species and genus levels; however, some sequences did not correspond to any of the species available on GenBank. The parasite–host network suggests that most of the helminths recorded in bats were host-specific. The highest helminth richness was found in insectivorous bats. This study increases our knowledge of helminths parasitizing Neotropical bats, adding new records and nucleotide sequences.

The study of Acari associated with cricetid rodents in Mexico began at the end of the 1930s. Despite efforts to gathering the information, only listings were built, but none of these studies present an analysis of the available data. A search was made through electronic databases; in addition, some not published records contained at Collection of Laboratorio de Acarología, Facultad de Ciencias, Universidad Nacional Autónoma de México were included in the inventory. Combining the literature records and those deposited in the collection, the total number of species of Acari associated with this family of rodents is 165, distributed in two superorders, four orders, 15 families, and 57 genera. Of the 15 families registered, the richest is Trombiculidae (70 nominal species and 75 taxa), followed by Laelapidae (39 and 42, respectively), Ixodidae (13 nominal and 16 taxa), and Leewenhoekiidae (13 nominal and taxa). From the bibliographic searches, a total of 76 papers were recovered with information on the association between Acari and cricetid rodents in Mexico. The main detected approach in the literature was taxonomic (75 works) and one on detection of pathogens. From the 145 known species of cricetids recorded in Mexico, only 72 (distributed in 18 genera) have been studied and found to host Acari. The use of regionalization of Mexico in provinces allowed us to map the records of Acari associated to cricetids in the most natural approximation of their distribution. We recognize and discuss seven factors that favor the scarcity and asymmetry of acarological studies in Mexico.

Peruanocotyle pelagica n. sp. is described based on specimens collected from the wall of the pharyngeal cavity of the Pacific cownose ray Rhinoptera steindachneri offshore Oaxaca and Guerrero, Mexico. The new species is distinguished from Peruanocotyle chisholmae by its anchors, which include a slender guard that curves towards the tip of the blade and which lack an accessory piece, morphological differences of the seminal vesicle, the lack of a male copulatory organ accessory piece and a greater number of spines, and an unsclerotized vagina. Molecular data of Peruanocotyle pelagica were generated to place the phylogenetic position of the genus within Monocotylidae.

We present a taxonomic, spatial, and thematic overview of the current state of knowledge on helminth parasites of Mexican amphibians. Sixty-six host species have been studied so far, representing 17.5% of the amphibian species distributed in Mexico. A total of 139 nominal species of helminths – 68 platyhelminths, 62 nematodes, three acanthocephalans, three annelids (hirudineans), and three arthropods (pentastomids) – have been recorded parasitizing these hosts. Most taxa found in larval stages have not been identified at the species level. The gastrointestinal nematodeAplectana itzocanensisexhibits the broadest host range, while the bladder flukeGorgoderina attenuataandA. itzocanensisshow the widest geographic distribution. Our analysis of helminthological studies evidenced gaps and biases on research efforts that have been devoted to relatively few host species, regions, and approaches. Most helminthological records come from two species, the cane toadRhinella marinaand the Montezuma's frogLithobates montezumae, and most studies have focused on describing the helminth fauna of a host species in a particular location or on the description of new helminth species. The highest proportion of records corresponds to the Veracruzan biogeographic province, and helminth richness is significantly correlated with host richness and with total amphibian richness by biogeographic province. Only three provinces (Yucatan Peninsula, Pacific Lowlands, and Baja Californian) have positive, yet still low helminth species discovery effort. Based on our findings, we recommend pursuing research approaches unexplored in Mexico and we provide guidelines to improve research on helminths parasitizing amphibians.

"The present study reports for the first time the occurrence of Hydatigera taeniaeformis (Cestoda: Taeniidae) in the Yucatán squirrel Sciurus yucatanensis (Rodentia: Sciuridae) in Yucatán, México. Thirty larval stages of cestodes were collected in the liver and mesenteries of an adult male squirrel. This study increases to 11 the total number of helminth taxa known from squirrels in México."

Human population is exposed to numerous parasitic ichthyozoonoses. Although Tamaulipas state (northeastern Mexico) is well known for its fishing and aquaculture industry, there are few reports of this type of zoonosis. Therefore, it is imperative to investigate whether the parasites that affect these fish may represent a zoonotic risk for the inhabitants of the area. The objective of this study was to identify molecular and/or morphologically muscle parasites of fish from coastal locations in Tamaulipas, Mexico, and assess the risk of infection for humans. Between 2017 and 2018, 764 individual fish belonging to 28 species were examined for parasites. Collected worms were processed for their identification using morphological characteristics. In addition, partial sequences of the large subunit (28S) ribosomal RNA gene were obtained from some species to corroborate their identity. Prevalence and mean intensity of all registered infections were calculated. A total of seven species of parasites were found: cestodes (Poecilancistrium caryophyllum), trematodes (Clinostomum tataxumui, Clinostomum cichlidorum), nematodes (Eustrongylides sp., Contracaecum sp.) and pentastomids (Sebekia purdieae, Sebekia sp.). Parasites infected 10 species belonging to different fish families (Ariidae, Centrarchidae, Centropomidae, Cichlidae, Eleotridae, Ictaluridae, Mugilidae and Sciaenidae). Congeneric species of parasites or related to those registered in this study have been identified as zoonotic agents in other regions of the world. Despite the low levels of infection (2.6-16.6% prevalence and 1-5.5 parasites per infected host), there is a latent risk of transmission to humans, so it is recommended to avoid eating raw or undercooked fish meat.

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.

Hymenolepis diminuta is a zoonotic cestode parasitizing the small intestine of rodents (definitive hosts). Humans can accidentally enter into the life cycle of this tapeworm via the ingestion of infected insects (intermediate hosts) containing cestode cysticercoids in their body cavity. More than two centuries after the first record in humans, there are no accurate estimates of the number of human cases around the world. In order to have a more precise idea about the number of human cases with H. diminuta and the current status of the disease (hymenolepiasis) worldwide, we conducted a literature review of published records on human infection with H. diminuta. One thousand five hundred and sixty-one published records of infection with H. diminuta from 80 countries were identified. This review presents an estimate of the number of human cases with H. diminuta and a current overview of the prevalence, geographic distribution, symptoms, diagnosis, exposure to infective stages, and therapeutic approaches for this underestimated zoonotic tapeworm., Centro de Estudios Parasitológicos y de Vectores

In this work, we document for the first time four species of Ichthyostraca in Mexico, one Branchiura: Argulus foliaceus (fish parasite), and three Pentastomida: Porocephalus clavatus (reptile parasite), Raillietiella hebitihamata (reptile parasite) and Raillietiella orientalis (frog parasite). In addition, a total of 11 new host records and 16 new localities are presented for Ichthyostraca in Mexico. Based on the compilation of published information and on specimens deposited in scientific collections, the first checklist of Ichthyostraca from North America (Canada, United States of America and Mexico) is compiled. To March 2019, records of Ichthyostraca from North America include 64 species and 8 undetermined taxa, parasitizing 293 host species (64 of them identified only to a supra-specific level) in 77 provinces and states (8 from Canada, 47 from the USA, and 22 from Mexico). The subclass Branchiura is represented by 1 order, 1 family, 1 genus, 35 species and 1 undetermined taxa; the subclass Pentastomida includes records of 4 orders, 9 families, 14 genera, 29 species and 7 undetermined taxa. Ten species reported in this work are thought to be introduced into North America with only a few records of them parasitizing native hosts. This checklist summarizes the available records of this class of crustaceans in North America and represents a base line for future studies.

During November 2010, a tarabundi vole, Microtus oaxacensis Goodwin, 1966 and 2 Mexican harvest mice, Reithrodontomys mexicanus Sassure, 1860 collected in Oaxaca, Mexico, were examined for helminths. The nematode Aspiculuris mexicana n. sp., was found in the colon of both species. This parasite is characterized by 2 clear synapomorphies: 1) cervical alae ending abruptly at the middle-length of esophageal bulb, and 2) the presence of 16 caudal papillae with unique arrangement: 3 preanal pairs; 1 pair adanal; a single papilla immediately postanal; 2 postanal pairs; 1 single ventral papilla, and 1 ventral pair far away from the anus. In addition, this work presents an updated taxonomic key for 17 of the 20 valid species included in the genus.

Moniliformis ibunami n. sp., is described from the intestine of the transvolcanic deermouse Peromyscus hylocetes Merriam 1898 (Cricetidae) from Parque Nacional Nevado de Colima “El Floripondio”, Jalisco, Mexico. The new species can be distinguished morphologically from the other 18 congeneric species of Moniliformis by a combination of morphological and molecular characters including the number of hooks on the proboscis (12 longitudinal rows, each one with six to eight transversally arranged unrooted hooks), the proboscis length (230–270 μm), the female trunk length (159–186 mm) and egg size (40–70 × 20–40). For molecular distinction, nearly complete sequences of the small subunit (SSU) and large subunit (LSU) of the nuclear ribosomal DNA and cytochrome oxidase subunit 1 (cox 1) of the mitochondrial DNA of the new species were obtained and compared with available sequences downloaded from GenBank. Phylogenetic analyses inferred with the three molecular markers consistently showed that Moniliformis ibunami n. sp. is sister to other congeneric species of Moniliformis. The genetic distance with cox 1 gene among Moniliformis ibunami n. sp., M. saudi, M. cryptosaudi, M. kalahariensis, M. necromysi and M. moniliformis ranged from 20 to 27%. Morphological evidence and high genetic distance, plus the phylogenetic analyses, indicate that acanthocephalans collected from the intestines of transvolcanic deer mice represent a new species which constitutes the seventh species of the genus Moniliformis in the Americas.

313 nominal species of monogenean parasites of aquatic vertebrates occurring in Mexico are included in this checklist; in addition, records of 54 undetermined taxa are also listed. All the monogeneans registered are associated with 363 vertebrate host taxa, and distributed in 498 localities pertaining to 29 of the 32 states of the Mexican Republic. The checklist contains updated information on their hosts, habitat, and distributional records. We revise the species list according to current schemes of classification for the group. The checklist also included the published records in the last 11 years, since the latest list was made in 2006. We also included taxon mentioned in thesis and informal literature. As a result of our review, numerous records presented in the list published in 2006 were modified since inaccuracies and incomplete data were identified. Even though the inventory of the monogenean fauna occurring in Mexican vertebrates is far from complete, the data contained in our checklist depict the actual knowledge about this group of flatworms in Mexico.

During August 2010, a total of 66 cane toad Rhinella marina were collected in Laguna de Coyuca, Guerrero, Mexico and examined for the presence of helminths. Ninety-two percent were parasitized by 1 or more parasite species. A total of 4624 individuals were found, belonging to 8 helminth taxa (1 digenean, 1 cestode and 6 nematodes). Infracommunities harbored by this host species are highly variable (mean Jaccard similarity index 0.31±0.27); mean percent similarity index 0.26±0.32) and depauperate (mean richness 1.91±0.92; mean abundance 64.4±100.34); almost 50% of them were dominated by Rhabdias fuelleborni, a skin-penetrating nematode. Differences related to host gender and size were found, since males registered infracommunities with lower species richness and diversity than females. The reproductive condition of females (collected during the breeding season) might explain the results obtained; during this season, females invest less in resistance to infection in favor of investing resources in reproduction. However, confirmation of this statement can only be made by sampling in the dry season, when the toads do not reach their reproductive peak.

During August 2016 we sampled fish from Vicente Guerrero Reservoir (also known as Las Adjuntas Reservoir), Tamaulipas, Mexico to increase the inventory of endohelminths parasitizing 3 species of fish inhabiting this water body and to identify their possible zoonotic potential. We collected 2 introduced species of fish, Cyprinus carpio (n = 10) and Oreochromis aureus (n = 15), and 1 native species, Micropterus salmoides (n = 17). The 2 introduced species were examined for parasites for the first time from this reservoir. As result, we found 4 species of parasite: 2 larvae of nematodes (Contracaecum sp. and Spiroxys sp.) and 2 trematodes (Posthodiplostomum minimum in the larval stage and adults of Saccocoelioides sp.), but none with zoonotic potential. Only nematodes parasitized 2 species of fish, but their prevalence and mean intensities were not significantly different between the host species. This work is the first parasitological study of O. aureus in Tamaulipas, and the records of the tremat...

Studies on helminth communities associated with didelphids are scarce; the majority of works have focused at taxonomic level. To increase the ecological knowledge of these host-parasite associations, during March (dry season) of 3 consecutive years (2013-2015) a total of 49 adults of the gray four-eyed opossum (

During 2009 and 2010, 87 specimens of the smooth-backed frog, Lithobates psilonota, from 2 localities (Atenquique and Zapopan) in the state of Jalisco, Mexico, were collected and analyzed for helminths. A total of 816 helminth specimens representing 9 species (7 adults and 2 larvae) were collected. The helminthological record for this host species is composed by 5 digeneans, 3 nematodes, and 1 acanthocephalan. Hosts from both sites shared the nematode Foleyellides sp. and the digeneans Haematoloechus sp., Megalodiscus americanus, and Glypthelmins quieta. On the other hand, Halipegus psilonota, Gorgoderina sp. (Trematoda), Eustrongylides sp., and Rhabdias sp. (Nematoda) were exclusively found in frogs from Atenquique. The acanthocephalan Oncicola sp. was found only in hosts from Zapopan. The most prevalent helminth species in both localities was M. americanus, reaching the highest levels in hosts from Atenquique. The composition of the helminthological record of L. psilonota is compared with tho...

A total of 22 specimens of the red-spotted toad collected from San Jose Brook, Baja California Sur, Mexico were examined for helminth parasites. The only parasite species recovered was the adult cestode Distoichometra bufonis, which was found parasitizing the intestine with a prevalence of 27% and mean abundance of 0.59. This report represents the first record for a helminth species in the red-spotted toad in Mexico. This tapeworm occurs naturally in the Nearctic region (Canada, United States, and Mexico), parasitizing 23 host species belonging to 10 genera and 5 anuran families.

The main objectives of this study were to report the parasites found in 16 Boa constrictor Linnaeus, 1758 captive in the Environmental Management Unit “El Palapo” Colima, Mexico, from 2013 to 2015, as well as to describe their pathological effects. All snakes had at least a parasite infection or a metabolic alteration. The parasites recorded include 1 Ascomycota ( Aspergillus sp.); 1 Actinobacteria ( Mycobacterium sp.); 2 Apicomplexa ( Hepatozoon sp. and Cryptosporidium sp.); 1 cestode ( Crepidobothrium sp.); 1 nematode ( Macdonaldius oschei Chabaud et Frank, 1961); and 3 Arthropoda [ Ophionyssus natricis (Gervais, 1844), Amblyomma dissimile Koch, 1844 (Acari) and Porocephalus sp. (Maxillopoda)]. The pathological effects recorded consisted of: visceral gout (in 31.2% of the snakes); granulomatous pneumonia (12.5%); erythrocytic hypertrophy (25%); heterophilic gastritis (18.7%) and enteritis (25%); heterophilic thrombosis and vasculitis (6.25%); heterophilic dermatitis (25%), and finally, focal pneumonitis (6.25%). The captivity of these snakes, without the support of preventive medicine, should be considered as a risk factor for the manifestation or exacerbation of metabolic and infectious pathologies.

Three monogenean taxa (Hargicola oligoplites, Mazocraes sp., and Neohexostoma euthynni) are recorded for marine fishes from the Gulf of Nicoya, Costa Rica. Two of them (Mazocraes sp. and N. euthynni) represent new records for the helminth fauna of Costa Rica.

Thirty specimens of the Montezuma's frog Lithobates montezumae were collected in San Pedro Tlaltizapán, in the Nearctic-Neotropical transition zone of Mexico, in April 2013, in order to establish the helminth infracommunity structure harbored by this amphibian host. A total of 5,493 individual helminths were obtained, representing 6 species (3 trematodes and 3 nematodes). The depauperate structure of the helminth infracommunities established for the studied frogs herein (richness = 2.4; mean abundance = 183.1; Brillouin's diversity = 0.42) fits with those described for the 6 Ranidae species studied in the Nearctic. Three of the 6 species of helminths recovered are generalists, 2 of them with the highest values for prevalence ( Falcaustra mexicana) and mean abundance ( Renifer sp.). The parasite recruitment process (ingestion) determining mean richness in the helminth infracommunities studied here (ingestion) is shared with those reported for the 9 Mexican frog species for which helminthological records exist; however, in this case, mean abundance was determined by directly penetrating species. The use of aquatic habits by this anuran species likely explains why the composition of their helminth infracommunities was mainly constituted of helminths acquired in this environment (5 of 6 species). Finally, the heterogeneity of their taxonomic composition and abundance of helminth species indicate the unpredictable nature of these host-parasite associations.

Asexually proliferatingTaenia crassiceps(Zeder, 1800) metacestodes isolated within past decades have been successfully sub-cultured under experimental conditions usingMus musculusLinnaeus, 1758 mice. However, during their development, morphological irregularities of scolex structures have been reported in two of the three strains of this cestode species maintained in mice – ORF and KBS. The main goal of this work is to describe the abnormalities observed in a sample of 118 cysticerci of the thirdT.crassicepsstrain used at present – WFU. Morphological abnormalities were detected in 39.8% of the evaginated scoleces; they consisted of supernumerary suckers (n= 2), duplicated (n= 2) or absent rostellum (n= 1), as well as absent or aberrant (n= 29) hooks, which were significantly shorter when compared to the large and short hook lengths referred to in the literature.

From August 2011 to November 2013, 68 opossums (8 Didelphis sp., 40 Didelphis virginiana, 15 Didelphis marsupialis, and 5 Philander opossum) were collected in 18 localities from 12 Mexican states. A total of 12,188 helminths representing 21 taxa were identified (6 trematodes, 2 cestodes, 3 acanthocephalans and 10 nematodes). Sixty-six new locality records, 9 new host records, and one species, the trematode Brachylaima didelphus, is added to the composition of the helminth fauna of the opossums in Mexico. These data, in conjunction with previous records, bring the number of taxa parasitizing the Mexican terrestrial marsupials to 41. Among these species, we recognized a group of helminths typical of didelphids in other parts of the Americas. This group is constituted by the trematode Rhopalias coronatus, the acanthocephalan Oligacanthorhynchus microcephalus and the nematodes Cruzia tentaculata, Gnathostoma turgidum, and Turgida turgida. In general, the helminth fauna of each didelphid species showed a stable taxonomic composition with respect to previously sampled sites. This situation suggests that the rate of accumulation of helminth species in the inventory of these 3 species of terrestrial marsupials in the Neotropical portion of Mexico is decreasing; however, new samplings in the Nearctic portion of this country will probably increase the richness of the helminthological inventory of this group of mammals.

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.

As a part of the revision of unidentified specimens harbored by the Coleccion Nacional de Helmintos of the Instituto de Biologia, Universidad Nacional Autonoma de Mexico, we studied several specimens of trematodes collected and processed between 1950 and 1980 in marine fishes from several localities along the Pacific coast of Mexico. Among these specimens, we found 1 undescribed species of the genus Pseudopecoelus von Wicklen, 1946 ( Pseudopecoelus ibunami n. sp.) of the intestine of the spotted grouper Epinephelus analogus Gill, 1863 (Actinopterygii: Serranidae) from Bahia de La Paz, Baja California Sur. This species is the number 40 known for this genus worldwide and the fifth registered parasitizing fishes from Mexico. The new species differs from the 17 species of Pseudopecoelus with vitelline follicles distributed anteriorly to ventral sucker by having a combination of the following traits: 1) body elongate, narrow, with irregular posterior end, 2) testes and ovary deeply-lobed, and 3) external seminal vesicle reaching only the anterior margin of ventral sucker. In addition, in this study we present new host and geographical records for 6 species of trematodes in marine fishes from Mexico and Pachycreadium gastrocotylum (Manter, 1940) Manter, 1954 is recorded for the first time in this country.

A new genus and species of nematode,Tziminema unachin. gen., n. sp. is described from the caecum and colon of Baird's tapirTapirus bairdii(Gill, 1865), found dead in the Reserva de la Biósfera El Triunfo, Chiapas State, in the Neotropical realm of Mexico.Tzimineman. gen. differs from the other nine genera included in the Strongylinae by two main characteristics: having 7–9 posteriorly directed tooth-like structures at the anterior end of the buccal capsule, and the external surface of the buccal capsule being heavily striated. Phylogenetic analyses of the DNA sequences of the mitochondrial cytochromecoxidase and nuclear DNA, including a partial sequence of the internal transcribed spacer 1, 5.8S and a partial sequence of the internal transcribed spacer 2 of the new taxon, confirmed its inclusion in Strongylinae and its rank as a new genus.

Species of Mesocoelium Odhner, 1901 (Digenea) are generally similar and are often difficult to distinguish. Currently there are 42 specimens of this genus held in the Coleccion Nacional de Helmintos (CNHE) of the Instituto de Biologia, Universidad Nacional Autonoma de Mexico, which previously have been assigned to three species: M. monas Rudolphi, 1819, M. travassosi Pereira & Cuocolo, 1940 and M. leiperi Bhalerao, 1936. Upon reevaluation of these specimens it was determined that 27, could not be assigned to species level and 15 could only be assigned to body type (carli and leiperi) because of the poor conditions of preservation of the material. The remaining 15 specimens were of sufficient quality to be identified to species and were found to represent M. americanum Harwood, 1932, M. danforthi Hoffman, 1935, M. meggitti Bhalerao, 1927, M. cf. americanum Harwood, 1932, and M. cf. danforthi Hoffman, 1935. Neither M. monas nor M. travassosi could be confirmed among these specimens; however, Mesocoelium meggitti (syn. M. travassosi ) was confirmed. Mesocoelium danforthi is recorded for the first time in the Mexican collection. The presence of M. cf. gonocephali Singh, 1967 and M. cf. microon Nicoll, 1914 also among the 15 specimens of sufficient quality to be identified to species, needs to be confirmed through collects of new material. Finally, in future studies, we propose to improve the quality of specimens by fixing them considering the modifications to this process proposed herein, and compliment these morphological studies with molecular studies.

The Asian fish tapeworm,Schyzocotyle acheilognathi(syn.Bothriocephalus acheilognathi) represents a threat to freshwater fish, mainly cyprinids, across the globe. This tapeworm possesses an extraordinary ability to adapt to different environmental conditions and, because of that, from its natural geographical origin in mainland Asia, it has colonized every continent except Antarctica. It is thought that this pathogenic tapeworm was first co-introduced into Mexico in 1965 from China, with the grass carpCtenopharyngodon idella, although the first formal record of its presence was published in 1981. Over the past 35 years, the Asian fish tapeworm has invaded about 22% of the freshwater fish in Mexico. Because fish communities in Mexico are characterized by high species richness and levels of endemism,S. acheilognathiis considered as a co-introduced and co-invasive species. In this review, we update the geographic distribution and host spectrum of the Asian fish tapeworm in Mexico. Up until December 2016, the tapeworm had been recorded in 110 freshwater fish species (96 native and 14 introduced), included in 51 genera, 11 families and 4 orders; it was also widely distributed in all types of aquatic environments, and has been found in 214 localities. We present novel data from a survey aimed at establishing the distribution pattern of the tapeworm in native freshwater fishes of two rivers in north-central Mexico, and the genetic variation among individuals of this co-invasive species collected from different host species and localities. We discuss briefly the factors that have determined the remarkable invasive success of this parasite in freshwater systems in Mexico.

article i nfo Keywords: Digenea Mexico Parastrigea Phylogeny ITSs Cox 1 Parastrigea plataleae n. sp. (Digenea: Strigeidae) is described from the intestine of the roseate spoonbill Platalea ajaja(Threskiornithidae) from four localities on the Pacific coast of Mexico. The new species is mainly distinguished from the other 18 described species of Parastrigea based on the ratio of its hindbody length to forebody length. A principal component analysis (PCA) of 16 morphometric traits for 15 specimens of P. plataleae n. sp., five of Parastrigea cincta and 11 of Parastrigea diovadena previously recorded in Mexico, clearly shows three clusters, which correspond to the three species. DNA sequences of the internal transcribed spacers (ITSs) of ribosomal DNA and the mitochondrial gene cytochrome c oxidase subunit I (cox 1) were used to corroborate this morpho- logical distinction. The genetic divergence estimated among P. plataleae n. sp., P. cincta and P. diovadena ranged from0.5 to1.48% for ITSs and from9.31to 11.47%forcox1.Maximum parsimony(MP)and maximum likelihood (ML) analyses were performed on the combined datasets (ITSs + cox 1) and on each dataset alone. All of the phylogenetic analyses indicated that the specimens from the roseate spoonbill represent a clade with strong bootstrap support. The morphological evidence and the genetic divergence in combination with the reciprocal monophyly in all of the phylogenetic trees support the hypothesis that the digeneans found in the intestines of roseate spoonbills represent a new species.

Studies on helminth communities associated with didelphids are scarce; the majority of works have focused at taxonomic level. To increase the ecological knowledge of these host-parasite associations, during March (dry season) of 3 consecutive years (2013-2015) a total of 49 adults of the gray four-eyed opossum (Philander opossum) was collected in the Neotropical portion of Mexico (Agua Fria, Chiapas State) and examined for helminths. The main objectives of this study were to describe the infra- and component communities of helminths associated with P. opossum and to compare the helminth fauna of the Mexican population of this host species with those studied in French Guiana and in other Mexican terrestrial didelphids. The helminthological record of this host consisted of 12 species: 7 taxa of Nematoda, 3 of Trematoda, 1 Cestoda, and 1 Acanthocephala. Eight of the 12 taxa have been previously recorded in Didelphidae and 4 represent accidental infections ( Glossocercus sp., Stomylotrema vicarium, Spirura mexicana and Acanthocephala gen. sp.). Diet of hosts is the main structuring factor of the communities (92% of the helminth species were recruited through ingestion). Forty-eight hosts were parasitized by at least 1 helminth species; Rhopalias coronatus was the most prevalent and abundant species in the hosts sampled. No significant differences were found in global prevalence among the helminth species present in all samplings, considering host sex and year. The dominance exerted by R. coronatus led to low values of evenness and diversity at both community levels. No significant differences were observed in composition of helminth species among the 3 sampling years regarding sex. The results of our study showed changes in helminth abundance at infracommunity level; during the first sampling these changes are explained by species with direct life cycle ( Viannaia sp. and Cruzia tentaculata), whereas in last 2 surveys the explanation can be attributed to species with heteroxenous life cycles (particularly R. coronatus, Duboisiella proloba, and Turgida turgida). Thirty-three percent of the helminth species recorded in P. opossum in Agua Fria is shared with the other 2 terrestrial species of didelphids sampled in different sites of Mexico: Didelphis marsupialis and Didelphis virginiana. In contrast, samples from French Guiana and Agua Fria, differ in terms of helminth fauna, confirming that the helminth communities of opossum species inhabiting the same locality show higher levels of taxonomic similarity than communities of conspecific marsupials allopatrically distributed.