Three new species of Gyrodactylus von Nordmann, 1832 described from Goodea atripinnis (Pisces: Goodeidae), an endemic freshwater fish from the central highlands of Mexico.

Goodea atripinnis Jordan, 1880 has a broad range of habitats and is the most widespread species of the endemic goodeid fishes, which inhabit the central highlands of Mexico. This species is known to be host to a high diversity of helminth parasites from which only three belong to the genus Gyrodactylus von Nordmann, 1832: G. lamothei Mendoza-Palmero, Sereno-Uribe et Salgado-Maldonado, 2009, G. mexicanus Mendoza-Palmero, Sereno-Uribe et Salgado-Maldonado, 2009, and G. tomahuac Rubio-Godoy, Razo-Mendivil, García-Vásquez, Freeman, Shinn et Paladini, 2016. Here, we describe three new species of Gyrodactylus collected from G. atripinnis, which were characterised morphologically (sclerites of the attachment apparatus) and molecularly (sequences of the internal transcribed spacer region of the rDNA): Gyrodactylus iunuri n. sp., Gyrodactylus katamba n. sp. and Gyrodactylus tepari n. sp. These new species were collected in three different states in the Mexican Highlands: Guanajuato, Jalisco and Querétaro. Both morphological and molecular data support the hypothesis that two distinct groups of gyrodactylids infect goodeid fishes: G. iunuri n. sp., G. tepari n. sp. and G. tomahuac possess robust hamuli and are closely related phylogenetically; while G. katamba n. sp. resembles G. lamothei in having slender hamuli with accessory sclerites adjacent to the hamuli root, and apparently shares a common ancestor with gyrodactylids infecting poeciliid fishes. New locality records of G. tomahuac are presented. The addition of the three new species of Gyrodactylus as parasites of G. atripinnis makes monogeneans the second most abundant parasite group known to infect this host.

Triple trouble? Invasive poeciliid fishes carry the introduced tilapia pathogen Gyrodactylus cichlidarum in the Mexican highlands.

As part of ongoing surveys of the gyrodactylid parasite fauna of freshwater fishes in Mexico, we recorded the infection of three species of poeciliids (Poecilia mexicana, Poeciliopsis gracilis, and Pseudoxiphophorus bimaculatus [syn.=Heterandria bimaculata]) with Gyrodactylus cichlidarum, a monogenean parasite of cichlid fishes, which has been co-introduced globally with its translocated, African "tilapia" hosts. This tilapia pathogen was found on poeciliid fishes both within their native distribution range in the Gulf of Mexico slope, as well as on invasive species artificially introduced to the Mexican highlands, to rivers draining into the Pacific Ocean. Identity of G. cichlidarum was confirmed by morphological and molecular analyses. Prevalence and abundance of infection were low, but this is the first record of G. cichlidarum infecting poeciliids (Cyprinodontiformes), which are distantly related to this parasite's primary cichlid fish hosts (Perciformes). This study provides evidence that G. cichlidarum, a recognized pathogen which has been co-introduced globally with its cichlid fish hosts for aquacultural purposes, is able to infect non-related poeciliid fishes inhabiting water bodies adjacent to tilapia farms, thereby potentially increasing its ability to disperse between farms and different river basins. It is of particular concern that G. cichlidarum was found on poeciliids, as these invasive fishes have been introduced worldwide and could act as carriers for this parasite known to induce significant mortality of farmed tilapias - globally, the second most important freshwater aquaculture fish group, after the carps.

To each his own: no evidence of gyrodactylid parasite host switches from invasive poeciliid fishes to Goodea atripinnis Jordan (Cyprinodontiformes: Goodeidae), the most dominant endemic freshwater goodeid fish in the Mexican Highlands.

BACKGROUND: Goodeid topminnows are live-bearing fishes endemic to the Mexican Highlands (Mesa Central, MC). Unfortunately, in the MC, environmental degradation and introduced species have pushed several goodeid species to the brink of extinction. Invasive fishes can introduce exotic parasites, and the most abundant goodeid, blackfin goodea Goodea atripinnis Jordan, is parasitised by six exotic helminths. Poeciliids are widely dispersed invasive fishes, which exert negative ecological effects on goodeids. Poeciliids host several species of the monogenean genus Gyrodactylus von Nordmann, 1832, including pathogenic, invasive parasites. Here, we looked for evidence of Gyrodactylus species switching hosts from poeciliids to goodeids. METHODS: Fish were collected in rivers draining the MC into both sides of the continental divide. Hosts were screened for gyrodactylid parasites in localities where G. atripinnis and poeciliids occurred sympatrically. Gyrodactylus specimens were characterised morphologically (attachment apparatus) and molecularly (internal transcribed spacer region, ITS). A Bayesian phylogenetic tree using ITS sequences established relationships between gyrodactylids collected from goodeid fishes and those from parasites infecting poeciliids. RESULTS: Gyrodactylids were collected from G. atripinnis in six localities on both sides of the watershed where exotic poeciliids occurred sympatrically. Morphological and molecular analyses indicated the presence of four undescribed species of Gyrodactylus infecting this goodeid host. Gyrodactylus tomahuac n. sp., the most abundant and geographically widespread species, is described here. The other three Gyrodactylus spp. are not described, but their ITS sequences are used as molecular data presented here, are the only available for gyrodactylids infecting goodeid fishes. Morphological and molecular data suggest that two distinct groups of gyrodactylids infect goodeids, one of which shares a common ancestor with gyrodactylids parasitizing poeciliids. CONCLUSIONS: No evidence was found of gyrodactylids switching hosts from invasive poeciliids to endemic goodeids, nor vice versa. Moreover, considering that G. atripinnis is known to host both Gyrodactylus lamothei Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009 and Gyrodactylus mexicanus Mendoza-Palmero, Sereno-Uribe & Salgado-Maldonado, 2009, with the addition of G. tomahuac n. sp. and the three undescribed Gyrodactylus spp. reported, at least six gyrodactylids may infect this host. This would make monogeneans the second most abundant parasite group infecting G. atripinnis, which to date is known to harbour 22 helminth species: nine digeneans, five nematodes, four cestodes, three monogeneans and one acanthocephalan.

Spot the difference: Two cryptic species of Gyrodactylus von Nordmann, 1832 (Platyhelminthes: Monogenea) infecting Astyanax aeneus (Actinopterygii, Characidae) in Mexico.

Over the course of one year, undescribed specimens of Gyrodactylus were recovered from banded tetra, Astyanax aeneus collected in the La Antigua and Nautla river basins in central Veracruz, Mexico. Parasites were processed for morphometric and molecular analyses. Morphometrically, Gyrodactylus samples collected in the La Antigua river had slightly smaller haptoral structures than those collected from the Nautla river. During the 12month-collection of samples, however, water temperature varied considerably (ca. 20°C to 30°C), and this abiotic factor is known to affect the size of gyrodactylid attachment structures. Moreover, no clear discrimination was possible between individual parasites collected from the two rivers based on the morphology of the marginal hook, which is recognised as a very informative character to discriminate between species. The morphology of the ventral bar, however, differed between specimens from both rivers: worms from Nautla all had long, rounded processes on the ventral bar, which formed a relatively closed angle with the dorsal edge of the bar proper, while most - but not all - specimens from La Antigua had comparatively slender processes forming a more open angle with respect to the ventral bar. Phylogenetic analyses based on the sequences of the ITS1, 5.8S rRNA gene, and ITS2 of gyrodactylids indicated the existence of two distinct, well-supported lineages whose sequences differ by >4%, one of which was only found in the Nautla basin, while the other was collected in both river systems. A posteriori, principal component analysis (PCA) of the morphometric data of sequenced specimens indicated that features of the dorsal bar, the hamuli and the ventral bar enable discrimination between the two phylogenetic lineages. Based on these independent sources of information (morphometric and molecular data), two new species of Gyrodactylus are described: Gyrodactyluspakan n. sp. and Gyrodactylusteken n. sp. The phylogenetic relationships of both new species to other gyrodactylids infecting characiformes (for which molecular data are available) are presented, which suggests that their closest relative is Gyrodactylus carolinae, a parasite of Characidium lanei in Brazil.

Morphological and molecular description of eight new species of Gyrodactylus von Nordmann, 1832 (Platyhelminthes: Monogenea) from poeciliid fishes, collected in their natural distribution range in the Gulf of Mexico slope, Mexico.

Eight new species of Gyrodactylus are described from Poecilia mexicana, Poeciliopsis gracilis, Pseudoxiphophorus bimaculatus [syn. = Heterandria bimaculata], and Xiphophorus hellerii collected in the Nautla and La Antigua River Basins in Veracruz, and in the Tecolutla River Basin in Puebla, Mexico. Analyzing the morphology of the marginal hooks, Gyrodactylus pseudobullatarudis n. sp. and Gyrodactylus xtachuna n. sp. are both very similar to Gyrodactylus bullatarudis; Gyrodactylus takoke n. sp. resembles Gyrodactylus xalapensis; Gyrodactylus lhkahuili n. sp. is similar to Gyrodactylus jarocho; and both Gyrodactylus microdactylus n. sp. and Gyrodactylus actzu n. sp. are similar to Gyrodactylus poeciliae in that all three species possess extremely short shaft points. A hypothesis of the systematic relationships of the eight new Gyrodactylus species and some of the known gyrodactylids infecting poeciliids was constructed with sequences of the Internal Transcribed Spacers (ITS1 and ITS2) and the 5.8S ribosomal gene of the rRNA. Phylogenetic trees showed that the new and previously described species of Gyrodactylus infecting poeciliid fishes do not form a monophyletic assemblage. Trees also showed that the eight new species described morphologically correspond to well-supported monophyletic groups; and that morphologically similar species are also phylogenetically close. Additionally, we correct previous erroneous records of the presence of Gyrodactylus bullatarudis on wild Poecilia mexicana and Xiphophorus hellerii collected in Mexico, as re-examination of the original specimens indicated that these corresponded to Gyrodactylus pseudobullatarudis n. sp. (infecting Poecilia mexicana and Xiphophorus hellerii) and to Gyrodactylus xtachuna n. sp. (on Xiphophorus hellerii). Finally, given the widespread anthropogenic translocation of poeciliid fishes for the aquarium trade and mosquito control programs, as well as the existence of invasive, feral poeciliid populations worldwide, we discuss the possibility that gyrodactylid parasites could be introduced along with the fish hosts-this work provides taxonomic information to assess that possibility, as it describes parasites collected from poeciliid fishes within their native distribution range.

A new species of Wallinia Pearse, 1920 (Digenea: Allocreadiidae) in Astyanax mexicanus (Characidae) from Mexico revealed by morphology and sequences of the 28S ribosomal RNA gene.

Wallinia mexicana sp. n. is described from the Mexican tetra, Astyanax mexicanus (De Filippi) (Characidae Weitzman), from two localities in northern Mexico. The new species can be distinguished from the two congeneric species, described from small-bodied characids in South and Central America, mainly by the posterior extent of the vitelline follicles (halfway between the posterior testis and the end of the caeca), by having a larger oesophagus, testes that are always oblique, and eye-spot remnants. The distinct status of the new species was confirmed by molecular data (28S rRNA gene sequences). Phylogenetic analysis suggests the new species is the sister species of W. chavarriae Choudhury, Hartvigsen et Brooks, 2002 described from characids in northwestern Costa Rica. Additionally, genetic divergence between these congeners reached 3.3%, a value higher than that observed for closely related species pairs of allocreadiids for that molecular marker. Based on these new findings, recently published records of this new species as Magnivitellinum simplex Kloss, 1966 and Creptotrematina aguirrepequenoi Jiménez-Guzmán, 1973 in Astyanax mexicanus from Durango and San Luis Potosi states, respectively, are corrected.

Genetic evidence for multiple sources of the non-native fish Cichlasoma urophthalmus (Günther; Mayan Cichlids) in southern Florida.

The number and diversity of source populations may influence the genetic diversity of newly introduced populations and affect the likelihood of their establishment and spread. We used the cytochrome b mitochondrial gene and nuclear microsatellite loci to identify the sources of a successful invader in southern Florida, USA, Cichlasoma urophthalmus (Mayan cichlid). Our cytochrome b data supported an introduction from Guatemala, while our microsatellite data suggested movement of Mayan Cichlids from the upper Yucatán Peninsula to Guatemala and introductions from Guatemala and Belize to Florida. The mismatch between mitochondrial and nuclear genomes suggests admixture of a female lineage from Guatemala, where all individuals were fixed for the mitochondrial haplotype found in the introduced population, and a more diverse but also relatively small number of individuals from Belize. The Florida cytochrome b haplotype appears to be absent from Belize (0 out of 136 fish screened from Belize had this haplotype). Genetic structure within the Florida population was minimal, indicating a panmictic population, while Mexican and Central American samples displayed more genetic subdivision. Individuals from the Upper Yucatán Peninsula and the Petén region of Guatemala were more genetically similar to each other than to fish from nearby sites and movement of Mayan Cichlids between these regions occurred thousands of generations ago, suggestive of pre-Columbian human transportation of Mayan Cichlids through this region. Mayan Cichlids present a rare example of cytonuclear disequilibrium and reduced genetic diversity in the introduced population that persists more than 30 years (at least 7-8 generations) after introduction. We suggest that hybridization occurred in ornamental fish farms in Florida and may contribute their establishment in the novel habitat. Hybridization prior to release may contribute to other successful invasions.

Testing the systematic position and relationships of Paracreptotrema heterandriae within the Allocreadiidae through partial 28s rRNA gene sequences.

The genus Paracreptotrema Choudhury, Pérez-Ponce de León, Brooks and Daverdin, 2006 (Digenea), comprises 4 species that parasitize poeciliid and cyprinodontid fishes in Middle America. Based on morphological characters exhibited by adults of the type species (Paracreptotrema blancoi Choudhury, Pérez-Ponce de León, Brooks and Daverdin, 2006 ) the genus was tentatively assigned to Allocreadiidae Looss, 1902. We sequenced domains D1-D3 of the 28S rRNA gene of several specimens of Paracreptotrema heterandriae Salgado-Maldonado, Caspeta-Mandujano and Vázquez, 2012 , and analyzed these in a phylogenetic context along with 10 allocreadiid taxa plus several xiphidiatan and 2 monorchiatan digeneans, in order to test the proposed inclusion of P. heterandriae in Allocreadiidae. Maximum likelihood and Bayesian inference analyses of 28S rRNA gene sequences confirmed the classification of Paracreptotrema as an allocreadiid. In the phylogenetic trees, Paracreptotrema appears to be the sister taxon of Creptotrematina aguirrepequenoi Jiménez-Guzmán, 1973, and both are closely related to Auriculostoma Scholz, Aguirre-Macedo, and Choudhury, 2004, with Wallinia Pearse, 1920, as the sister taxon of all these genera; nevertheless, the interrelationships between these 4 genera were not totally resolved. ITS2 sequences of several specimens of P. heterandriae showed null intraspecific variation. Scanning electron microscopy microphotograph demonstrated the presence of 13 and 4 dome-like papillae arranged around the outer and inner edges of the oral sucker, respectively.

A new species of Auriculostoma (Digenea: Allocreadiidae) in the Mexican tetra Astyanax mexicanus (Actinopterygii: Characidae) from Central Veracruz, Mexico, described with the use of morphological and molecular data.

Auriculostoma totonacapanensis n. sp. is described from the Mexican tetra, Astyanax mexicanus (Actinopterygii, Characidae) collected in a tributary creek of the Bobos River in Filipinas, Veracruz, Mexico. The new species is set apart from all congeners by the combination of some morphological characters such as the testes position (oblique in most specimens), the ventral to oral sucker ratio (1:1.2 × 1:1.1), the cirrus sac originating at the ovarian region, and by having vitelline follicles not confluent in the posttesticular region. Auriculostoma totonacapanensis n. sp. closely resembles Auriculostoma platense (Szidat, 1954) Scholz, Aguirre-Macedo, and Choudhury, 2004 and Auriculostoma diagonale Curran, Tkach and Overstreet, 2011 by possessing oblique testes; however, it differs from both species by possessing a genital pore located at level of the cecal bifurcation and by having vitelline follicles extending anteriorly up to the cecal bifurcation level, instead of a genital pore located between the anterior margin of the ventral sucker and cecal bifurcation, and vitelline follicles extending anteriorly to the mid level of the esophagus as in A. platense or to the pharynx level as in A. diagonale. Additionally, the new species differs from A. diagonale by having vitelline follicles not confluent or scarcely confluent in the posttesticular region rather than extensively confluent. Scanning electron microscopy micrographs of the new species demonstrated the presence of a single pair of muscular lobes on either side of the oral sucker, with a broad base, stretching from the ventrolateral to the dorsolateral side. Maximum parsimony and Bayesian inference analyses of the 28S rRNA gene sequences placed A. totonacapanensis as sister species of Auriculostoma astyanace Scholz, Aguirre-Macedo, and Choudhury, 2004 . Nucleotide variation between A. totonacapanensis and A. astyanace was 2.0% and 3.6% for the 28S rRNA gene and ITS2 sequences, respectively. Sequence variation for the 28S rRNA gene between Auriculostoma spp. and 7 other genera of Allocreadiidae ranged from 2.4 to 6.3%.

Integrative taxonomy identifies a new species of Phyllodistomum (Digenea: Gorgoderidae) from the twospot livebearer, Heterandria bimaculata (Teleostei: Poeciliidae), in Central Veracruz, Mexico.

Phyllodistomum inecoli n. sp. is described from the twospot livebearer, Heterandria bimaculata (Teleostei: Poeciliidae), collected in the Río La Antigua basin, Veracruz, Mexico. The new species is described and characterised by using a combination of morphology, scanning electron microscopy, and sequences of nuclear and mitochondrial genes. Diagnostic characters of the new species of Phyllodistomum include a genital pore opening at the level of the caecal bifurcation; oval vitellarium, situated just posterior to the ventral sucker and not extended laterally and anterior extracaecal uterine loops variable in extension (reaching the anterior, median or posterior margin of the ventral sucker). P. inecoli n. sp. most closely resembles P. brevicecum, a species described as a parasite of the central mudminnow, Umbra limi, in other parts of North America; however, the genital pore in P. brevicecum is situated between the caecal bifurcation and the ventral sucker, the ovary is larger, the vitellarium is lobed and extended laterally and the anterior portion of the uterus extends to the posterior margin of the ventral sucker. Comparison of about 1,500­2,200 nucleotides of cox1 and 28S rDNA and ITS1 strongly supports the status of P. inecoli as a new species. Bayesian inference analysis of combined datasets of 28S rDNA and cox1 sequences showed that P. inecoli n. sp. and the other species found in freshwater fishes of Mexico, including the species complex of P. lacustri, are not sister species. Phylogenetic analysis based on 28S rDNA sequences of several gorgoderid taxa revealed the close relationship of P. inecoli n. sp. with several species of Phyllodistomum, Gorgodera and Gorgoderina with cystocercous cercariae developing in sphaeriid bivalves. Dot-plot analysis of ITS1 sequences of P. inecoli n. sp. revealed the presence of eight repetitive elements with different length, which together represent almost half the length of ITS1.

Discordant genetic diversity and geographic patterns between Crassicutis cichlasomae (Digenea: Apocreadiidae) and its cichlid host, "Cichlasoma" urophthalmus (Osteichthyes: Cichlidae), in Middle-America.

Genetic analyses of hosts and their parasites are key to understand the evolutionary patterns and processes that have shaped host-parasite associations. We evaluated the genetic structure of the digenean Crassicutis cichlasomae and its most common host, the Mayan cichlid "Cichlasoma" urophthalmus, encompassing most of their geographical range in Middle-America (river basins in southeastern Mexico, Belize, and Guatemala together with the Yucatan Peninsula). Genetic diversity and structure analyses were done based on 167 cytochrome c oxidase subunit 1 sequences (330 bp) for C. cichlasomae from 21 populations and 161 cytochrome b sequences (599 bp) for "C." urophthalmus from 26 populations. Analyses performed included phylogenetic tree estimation under Bayesian inference and maximum likelihood analysis, genetic diversity, distance and structure estimates, haplotype networks, and demographic evaluations. Crassicutis cichlasomae showed high genetic diversity values and genetic structuring, corresponding with 4 groups clearly differentiated and highly divergent. Conversely, "C." urophthalmus showed low levels of genetic diversity and genetic differentiation, defined as 2 groups with low divergence and with no correspondence with geographical distribution. Our results show that species of cichlids parasitized by C. cichlasomae other than "C." urophthalmus, along with multiple colonization events and subsequent isolation in different basins, are likely factors that shaped the genetic structure of the parasite. Meanwhile, historical long-distance dispersal and drought periods during the Holocene, with significant population size reductions and fragmentations, are factors that could have shaped the genetic structure of the Mayan cichlid.

Testing the evolutionary and biogeographical history of Glypthelmins (Digenea: Plagiorchiida), a parasite of anurans, through a simultaneous analysis of molecular and morphological data.

The genus Glypthelmins includes some of the most common digeneans inhabiting the intestine of anurans in the Americas. Phylogenetic analyses of eight species of Glypthelmins and five outgroups, using 26 morphological characters and sequences of cox1, 18S, 5.8S, 28S genes and ITS2 were performed. Additionally, 2 species for which no molecular data have been obtained were included in the analyses. Following a simultaneous analysis approach and using different methods of phylogenetic inference we obtained a phylogenetic tree where the eight studied species conform a monophyletic clade which is well supported by Bremer support, bootstrap, and posterior probabilities. The mapping of morphological characters showed that traits such as serrate scale-like spines, bipartite seminal vesicle, metraterm running dorsal to the cirrus pouch, and ovary sinistral are unequivocal synapomorphies that support the monophyly of Glypthelmins. Phylogenetic hypothesis based on combined data sets was used to re-evaluate the evolutionary and biogeographical history of this group of digeneans. New information provided in this study, in the context of a more robust analytical method allowed us to corroborate that members of the "Rana pipiens" group were the plesiomorphic group of hosts for Glypthelmins, with two host switching events occurring from the "Rana pipiens" group to the "Rana palmipes" group and to Hylidae during the evolutionary history of this group of parasites, and the origin of the group is proposed in Nearctic frogs, with a colonization of Neotropical hosts represented by a monophyletic clade constituted by G. brownorumae, G. facioi, and G. tuxtlasensis.

Phylogenetic analysis of nuclear and mitochondrial DNA reveals a complex of cryptic species in Crassicutis cichlasomae (Digenea: Apocreadiidae), a parasite of Middle-American cichlids.

We obtained nuclear ITS-1 and mitochondrial cox1 sequences from 225 Crassicutis cichlasomae adults collected in 12 species of cichlids from 32 localities to prospect for the presence of cryptic species. This trematode is commonly found in species of cichlids over a wide geographic range in Middle-America. Population-level phylogenetic analyses of ITS-1 and cox1, assessments of genetic and haplotype diversity, and morphological observations revealed that C. cichlasomae represents a complex of seven cryptic species for which no morphological diagnostic characters have been discovered thus far. Bayesian and Maximum Likelihood analyses of concatenated datasets (906 bp) recovered eight lineages of C. cichlasomae, all with high posterior probabilities and bootstrap branch support. Values of genetic divergence between clades ranged from 1.0% to 5.2% for ITS-1, and from 7.2% to 30.0% for cox1. Morphological study of more than 300 individuals did not reveal structural diagnostic traits for the species defined using molecular evidence. These observations indicate that some traditional morphological characters (e.g., testes position) have substantial intra-specific variation, and should be used with caution when classifying C. cichlasomae and their sister taxa. Additionally, phylogenetic analyses did not reveal a strict correlation between these cryptic species and their host species or geographic distribution, however it appears that genetic distinctiveness of these cryptic species was influenced by the diversification and biogeographical history of Middle-American cichlids.

Detecting a complex of cryptic species within Neoechinorhynchus golvani (Acanthocephala: Neoechinorhynchidae) inferred from ITSs and LSU rDNA gene sequences.

Neoechinorhynchus golvani is an intestinal parasite of freshwater and brackish water fishes distributed in Mexico. The genetic variability of 40 samples representing 12 populations from north, south, and central Mexico, and 1 from Costa Rica, was estimated by sequencing 2 nuclear genes (ITS1, 5.8S, ITS2, and LSU rDNA, including the domain D2 + D3). The length of both genes ranged from 700 to 779 base pairs (bp) and from 813 to 821 bp, for ITSs and LSU, respectively. The genetic divergence among populations ranged from 19.5 to 35.3% with ITSs and from 9.28 to 19.58% with LSU. Maximum likelihood and maximum parsimony analyses were performed for each data set and also for 2 combined data sets (ITSs + LSU rDNA with and without outgroups), showing strong similarities among trees, with high bootstrap support in all cases. Genetic divergence, in combination with phylogenetic analyses, suggested that the acanthocephalan N. golvani represents a complex of cryptic species, which is composed of at least 3 lineages. The first lineage, corresponding with N. golvani, shows a wide distribution, including localities from northeastern Mexico, southwards through central and southeastern Mexico, and further down to Costa Rica. This lineage is associated with cichlid fishes in strictly freshwater environments. Lineages 2 and 3 are distributed in brackish water systems along the Gulf of Mexico and Pacific slopes, respectively; both are associated with eleotrid fishes, and apparently represent 2 cryptic species. The diversification of the eleotrid and cichlid lineages seems to be the result of independent host-switching events from the ancestral population.

A new cryptogonimid (Digenea) from the Mayan cichlid, Cichlasoma urophthalmus (Osteichthyes: Cichlidae), in several localities of the Yucatán Peninsula, Mexico.

Oligogonotylus mayae n.sp. is described from the intestine of the Mayan cichlid Cichlasoma urophthalmus (Günther) in Ría Lagartos, Ría Celestún, and Estero Progreso, Yucatán State. This is the second species described for Oligogonotylus Watson, 1976, the other being O.manteri Watson, 1976. The new species is readily distinguished from O. manteri by the anterior extension of the vitelline follicles. In O. Manteri, Vitelline follicles are found entirely in the hindbody, extending posteriorly to mid-testicular level. Vitelline follicles in the new species extend from teh anterior margin of posterior testis to the region between the bentral sucker and the pharynx. comparison of approximately 1,850 bases of ribosomal DNA (ITS1, ITS2, 5.8S, and 28S), and 400 bases of cytochrome c oxidase subunit I (cox1) strongly supports the status of O. mayae as a new species, as compared to O. manteri collected from cichlids in other localities of Mexico, Belize, and Guatemala.

Description of a new species of Crassicutis Manter, 1936, parasite of Cichlasoma beani Jordan (Osteichthyes: Cichlidae) in Mexico, based on morphology and sequences of the ITS1 and 28S ribosomal RNA genes.

A new species of Crassicutis Manter, 1936 is described from the Sinaloan cichlid Cichlasoma beani (Jordan) (Osteichthyes: Cichlidae) in the upper Río Santiago basin. Crassicutis choudhuryi n. sp. differs from most of the other nominal species by having testes located in a symmetrical position. The only other species of the genus that includes some specimens exhibiting this trait is Crassicutis intermedius (Szidat 1954), a species found in 5 species of siluriforms and 1 species of characiform in South America. However, this species differs from Cr. choudhuryi n. sp. by having testes almost half of the size, and vitelline follicles extending anteriorly to the region between the acetabulum and the intestinal bifurcation. The new species is morphologically very similar to Crassicutis cichlasomae Manter, 1936, but clearly differs from this species because of the constantly symmetrical position of the testes. Additionally, Cr. choudhuryi n. sp. is found in the Santiago River basin on the Pacific slope of Mexico, parasitizing specifically the endemic Ci. beani that does not co-occur with any other cichlid. Cr. cichlasomae exhibits more hosts (about 25 species of cichlids only in Mexico) and a wider distribution range that extends from northeastern Mexico southward to Central America, Cuba, and Brazil. To corroborate that our specimens were not conspecific with Cr. cichlasomae, sequences of the internal transcribed spacer (ITS1) and the 28S ribosomal RNA genes of individuals from several populations (recently collected in southeastern Mexico) were obtained and compared to the species described herein. Sequence divergence (1.3% for the 28S and 4.0% for the ITS1) gives further support to the erection of a new species.

Description of two new species of Glypthelmins Stafford, 1905 (Digenea: Macroderoididae) in Rana spp. from Mexico, based on morphology and mtDNA and rDNA sequences.

Glypthelmins Stafford, 1905 includes 29 putative species commonly found in the intestine and liver of anurans from all over the world but mainly in the Americas. Partial sequences of the cytochrome c oxidase subunit 1 ( cox 1), ribosomal internal transcribed spacer region 2 (ITS2) and the large subunit 28S rDNA gene were obtained and analysed using pairwise distance matrices and parsimony methods in order to characterise the interrelationships between 14 isolates of four nominal species of Glypthelmins recognised on morphological grounds. The highest intra-specific sequence divergence occurred in the cox 1 (18.53%) sequence, followed by that of the ITS2 (5.44%) and 28S (4.63%). Genetic variability was detected between the three isolates originally identified as G. facioi Brenes et al., 1959 from two localities in Mexico and one locality in Costa Rica. Sequence divergence exhibited among these isolates ranged from 10.70 to 11.22%, from 0.48 to 0.97% and from 1.33 to 1.88% for cox 1, ITS2 and 28S, respectively. Phylogenetic analysis combining all three data-sets generated a single most parsimonious tree. The three isolates of G. facioi form a clade, with an isolate collected from frogs in Veracruz State as the sister group to an isolate from Tabasco State + G. facioi from Costa Rica. The information derived from pairwise distance of independent data-sets plus the phylogenetic information indicate that each of the two isolates from Mexico, identified a priori as G. facioi, represent separate species. A re-examination of specimens was carried out and a re-evaluation made of the morphological characters to find reliable differences that had been overlooked. As a consequence, G. brownorumae n. sp. from Tabasco and G. tuxtlasensis n. sp. from Veracruz are described based on molecular and morphological differences.