Rogelio Rosas-Valdez

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.

Molecular prospecting for cryptic species in Phyllodistomum lacustri (Platyhelminthes, Gorgoderidae)

Rosas‐Valdez, R., Choudhury, A. & Pérez‐Ponce de León, G. (2011). Molecular prospecting for cryptic species in Phyllodistomum lacustri (Platyhelminthes, Gorgoderidae). —Zoologica Scripta, 40, 296–305.

Helminth parasites of freshwater fishes, Nazas River basin, northern Mexico

This paper represents the first study of the helminth parasites of freshwater fishes from the Nazas River basin in northern Mexico. Between July 2005 and December 2008, 906 individual fish were collected and examined for helminth parasites in 23 localities along the river basin. Twenty-three species of fish were examined as a part of this inventory work. In total, 41 helminth species were identified: 19 monogeneans, 10 digeneans, seven cestodes, one acanthocephalan, and four nematodes. The biogeographical implications of our findings are briefly discussed.

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.

The systematic position of Wallinia spp. and Margotrema spp. (Digenea), parasites of Middle-American and Neotropical freshwater fishes, based on the 28S ribosomal RNA gene

The systematic relationships of aspinose allocreadiid-like digeneans from Middle-American and Neotropical freshwater fishes, such as Wallinia Pearse, 1920, Margotrema Lamothe-Argumedo, 1970, Magnivitellinum Kloss, 1966 and other related genera, remain enigmatic. Wallinia (2 spp.) and Margotrema (2 spp.) have been placed in the subfamily Walliniinae, within the Macroderoididae. Recent descriptions of species in these genera have followed this classification but have raised questions about their affinities with macroderoidids. Partial sequences of the 28S rRNA gene of Walliniachavarriae Choudhury, Hartvigsen & Brooks, 2002 and Margotremabravoae Lamothe Argumedo, 1970, as representatives of their genera, were used in a phylogenetic analysis along with the available sequences of macroderoidids and allocreadiids. Results from Maximum Parsimony, Maximum Likelihood and Bayesian Analyses were identical in placing both genera into one clade along with allocreadiids rather than the macroderoidids. Margotrema was the sister group of Crepidostomum Braun, 1900, and Wallinia was the sister group of both Margotrema and Crepidostomum combined. Bootstrap and Bremer values, as well as posterior probabilities derived from Bayesian analysis strongly supported these relationships in three analyses.

PHYLOGENETIC ANALYSIS ON GENERA OF CORALLOBOTHRIINAE (CESTODA: PROTEOCEPHALIDEA) FROM NORTH AMERICAN ICTALURID FISHES, USING PARTIAL SEQUENCES OF THE 28S RIBOSOMAL GENE

Partial sequences of the 28S rDNA (ribosomal gene) were obtained from a total of 11 populations of 5 species (in 3 genera) of North American corallobothriine proteocephalideans. These included Corallobothrium fimbriatum (3 populations), Corallobothrium parafimbriatum (1 population), Corallotaenia minutia (1 population), Megathylacoides giganteum (2 populations), and Megathylacoides lamothei (4 populations). These sequences were used in a phylogenetic analysis to test the monophyly of Corallobothriinae and to investigate the interrelationships of the North American species. The results indicate that Corallobothriinae, as conventionally understood, is not monophyletic and that only the North American corallobothriines, parasites of ictalurid catfishes, form a monophyletic group. Corallobothrium parafimbriatum is sister taxon to a clade that includes Corallotaenia intermedia and C. minutia and not to its congener C. fimbriatum. Also, M. giganteum from Mexico appears to be more closely related to M. lamothei than to its conspecific in Canada. This and the amount of sequence divergence indicate possible cryptic speciation in its endemic host, the Lerma catfish, Ictalurus dugesi.

Patterns of Host Specificity Among the Helminth Parasite Fauna of Freshwater Siluriforms: Testing the Biogeographical Core Parasite Fauna Hypothesis

Abstract Host specificity plays an essential role in shaping the evolutionary history of host–parasite associations. In this study, an index of host specificity recently proposed was used to test, quantitatively, the hypothesis that some groups of parasites are characteristics of some host fish families along their distribution range. A database with all published records on the helminth parasites of freshwater siluriforms of Mexico was used. The host specificity index was used considering its advantage to measure the taxonomic heterogeneity of the host assemblages and its appropriateness for unequal sampling data. The helminth parasite fauna of freshwater siluriforms in Mexico seems to be specific for different host taxonomic categories. However, a relatively high number of species (47% of the total helminth fauna) is specific to their respective host family. This result provides further corroboration for the biogeographic hypothesis of the core helminth fauna proposed previously. The statistical values for host specificity obtained herein seem to be independent of host range. However, the accurate taxonomic identification of the parasites is fundamental for the evaluation of host specificity and the accurate evolutionary interpretation of this phenomenon.

Helminth fauna of two cyprinid fish (Campostoma ornatum and Codoma ornata) from the upper Piaxtla River, Northwestern Mexico

SummaryThe helminth parasite fauna of 2 species of freshwater fishes from the upper Piaxtla River in northwestern Mexico was studied. A total of 41 cyprinids, corresponding to 20 Campostoma ornatum and 21 Codoma ornata were analyzed. Six species of platyhelminths were recorded, including 2 species of monogeneans (Gyrodactylus sp. and Dactylogyrus sp.), 3 species of digeneans (Posthodiplostomum minimum, Clinostomum complanatum, and Margotrema sp.), and 1 species of tapeworm (Bothriocephalus acheilognathi). Helminth parasite infracommunities were depauperate, showed low richness and diversity values, and were dominated by 1 or 2 helminth species. This pattern is consistent with that observed for the helminth parasite communities in other freshwater fishes in central and northern Mexico.