Andrés Martínez-Aquino

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.

Helminth Parasites of Chapalichthys encaustus (Pisces: Goodeidae), an Endemic Freshwater Fish From Lake Chapala, Jalisco, Mexico

A total of 6 helminth species were recorded during helminthological examination of 50 Chapalichthys encaustus from Lake Chapala, Jalisco, Mexico. Helminth species identified included: Salsuginus sp. (an undescribed monogenea); Posthodiplostomum minimum (metacercariae); Cyclustera ralli (metacestode); Polymorphus brevis (cystacanth); Contracaecum sp. (nematode larvae); and Rhabdochona lichtenfelsi (adult nematode). Of these, 2 (Salsuginus sp. and R. lichtenfelsi) are specialist species. The observed species richness, individual parasite abundance, and diversity were low. Data suggest that host specificity is an important factor contributing to observed community composition and richness. Host feeding habits and helminth species availability seem to determine the characteristics of these helminth assemblages.

Helminth parasites of freshwater fishes from Cuatro Ciénegas, Coahuila, in the Chihuahuan Desert of Mexico: inventory and biogeographical implications.

As part of an ongoing inventory of the helminth parasites of freshwater fishes in Mexico, 570 individual fish were collected between Apr 2008 and Oct 2011 in 26 localities along the Cuatro Ciénegas region in Coahuila State, northern Mexico. Seventeen species of hosts, mostly corresponding to Nearctic freshwater elements, were studied. A total of 8324 individual worms were collected during this survey, representing 25 species of helminths, of which 9 were digeneans, 3 monogeneans, 3 acanthocephalans, 9 nematodes and 1 cestode. Most of the records in this checklist represent new host or locality records. The information provided in this checklist may be helpful for our understanding of the biodiversity and historical biogeography of this host-parasite system, because in the Cuatro Ciénegas region occur a Nearctic freshwater fish fauna, along with Neotropical and endemic elements, and from a biogeographical point of view, this may represent a transitional area.

Do the Historical Biogeography and Evolutionary History of the Digenean Margotrema spp. across Central Mexico Mirror Those of Their Freshwater Fish Hosts (Goodeinae)

Host-parasite systems provide an ideal platform to study evolution at different levels, including codivergence in a historical biogeography context. In this study we aim to describe biogeographic and codivergent patterns and associated processes of the Goodeinae freshwater fish and their digenean parasite (Margotrema spp.) over the last 6.5 Ma (million years), identifying the main factors (host and/or hydrogeomorphology) that influenced the evolution of Margotrema. We obtained a species tree for Margotrema spp. using DNA sequence data from mitochondrial and nuclear molecular markers (COI and ITS1, respectively) and performed molecular dating to discern divergence events within the genus. The dispersal-extinction-cladogenesis (DEC) model was used to describe the historical biogeography of digeneans and applied to cophylogenetic analyses of Margotrema and their goodeine hosts. Our results showed that the evolutionary history of Margotrema has been shaped in close association with its geographic context, especially with the geological history of central Mexico during the Pleistocene. Host-specificity has been established at three levels of historical association: a) Species-Species, represented by Xenotaenia resolanae-M. resolanae exclusively found in the Cuzalapa River Basin; b) Species-Lineage, represented by Characodon audax-M. bravoae Lineage II, exclusive to the Upper and Middle Mezquital River Basin, and c) Tribe-Lineage, including two instances of historical associations among parasites and hosts at the taxonomical level of tribe, one represented by Ilyodontini-M. bravoae Lineage I (distributed across the Ayuquila and Balsas River Basins), and another comprised of Girardinichthyini/Chapalichthyini-M. bravoae Lineage III, found only in the Lerma River Basin. We show that the evolutionary history of the parasites is, on several occasions, in agreement with the phylogenetic and biogeographic history of their hosts. A series of biogeographic and host-parasite events explain the codivergence patterns observed, in which cospeciation and colonisation via host-switching and vicariant plus dispersal events are appreciated, at different times during the diversification history of both associates, particularly during the Pleistocene.

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.

Helminth Parasites of Xenotaenia resolanae (Osteichthyes: Cyprinodontiformes: Goodeidae) From the Cuzalapa Hydrological System, Jalisco, Mexico

Abstract Six helminth species were recorded during the helminthological examination of 35 specimens of the goodeid Xenotaenia resolanae from Arroyo Durazno, Jalisco, Mexico, a tributary of the Cuzalapa River. Helminth species identified included: 4 species of digeneans, i.e., Posthodiplostomum minimum (metacercariae), Clinostomum companatum (metacercariae), Dendrorchis sp. (adult), and Margotrema guillerminae (adult); and 2 species of nematodes, i.e., Spiroxys sp. (larvae) and Rhabdochona ahuehuellensis (adult). A very low number of individual larvae were found. The observed species richness, individual parasite abundance, and diversity were low at both component community and infracommunity levels. The values of similarity between infracommunities were relatively high because of the predominance of the digenean M. guillerminae, the species that reached the higher values of both prevalence and abundance. High water flow of the collecting site is suggested as the main factor determining the depauperate helminth assemblage in this fish species.