No 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.

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.

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.