Ulises Razo-Mendivil

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

Abstract 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.

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.

A New Cryptogonimid (Digenea) From the Mayan Cichlid, Cichlasoma urophthalmus (Osteichthyes: Cichlidae), in Several Localities of the Yucatán Peninsula, Mexico

Abstract 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 the anterior margin of posterior testis to the region between the ventral 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.

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.

Abstract:  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%.

Testing the Systematic Position and Relationships of Paracreptotrema heterandriae Within the Allocreadiidae Through Partial 28s rRNA Gene Sequences

Abstract: 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.

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 1,500–2,200 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.

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.

The use of mitochondrial and nuclear sequences in prospecting for cryptic species in Tabascotrema verai (Digenea: Cryptogonimidae), a parasite of Petenia splendida (Cichlidae) in Middle America.

In this study, we used sequences of mitochondrial and nuclear markers to test the hypothesis that Tabascotrema verai Lamothe-Argumedo and Pineda-López, 1990, a parasite of the cichlid Petenia splendida Günther, 1862 in Middle America, represents a single species, following a molecular prospecting approach. One-hundred and five individuals of T. verai were collected from the intestine of 43 specimens of P. splendida in eight localities of Mexico, Belize and Guatemala. A portion (n=53) of the collected specimens was used for molecular studies, whereas the remaining individuals were processed for morphological studies. Fifty-three partial sequences of the cytochrome c oxidase subunit I (cox1) gene were obtained. In addition, 36 sequences of the ITS (internal transcribed spacers 1, 5.8S rRNA gene, and ITS2) and of the 28S rRNA gene were generated from most of the specimens that showed nucleotide variation with the cox1 gene. A haplotype network obtained from cox1 sequences revealed three independent groups (haplogroups 1, 2, and 3). Independent phylogenetic analyses performed with maximum likelihood and Bayesian inference of cox1, ITS and the 28S rRNA gene recovered three genetically-distinct and reciprocally-monophyletic groups, corresponding with the 3 haplogroups obtained in the haplotype network. Values of genetic divergence between clades for cox1 sequences ranged between 8.3% and 11.9%, while for ITS and the 28S rRNA gene, these ranged from 0.08% to 1.2% and from 0.3% to 0.4%, respectively. Morphological observations, and measurements of 23 characters of 44 mounted individuals, showed that no morphological differences exist between individuals from the eight collecting sites, and that the ranges of most morphological traits overlap. Our results suggest that the digenean T. verai represents a complex of cryptic species; the haplotype network, phylogenetic analyses, and genetic differences, along with the morphological stasis recorded here support this notion. Finally, the three recovered lineages showed neither geographical association nor correlation with drainage basins.

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.