The communities of helminth parasites of Heterandria bimaculata (Teleostei: Poeciliidae) from the upper Río La Antigua basin, east-central Mexico show a predictable structure

Distribution of different species of metacercariae in two freshwater fishes: Haludaria fasciata (Teleostei: Cyprinidae) and Pseudosphromenus cupanus (Teleostei: Osphromenidae)

Information on the distribution and abundance patterns of trematodes are essential to reveal the ecology of host-parasite interactions. The Western Ghats of India, a biodiversity hotspot, is rich in freshwater fish diversity and endemism. Though there are several studies on various other aspects of fish ecology, studies on their parasitic fauna is meager. The objective of the present study is to explore the distribution and infection patterns of metacercariae of five species of trematodes in the freshwater fishes, Haludaria fasciata and Pseudosphromenus cupanus. The infection parameters were analyzed for each host and CART model was applied to analyze the environmental factors affecting parasite distribution patterns. All species of metacercariae showed an over-dispersed aggregate distributions. The classification tree models indicated that among the environmental factors considered, differences in host locality was the most influential factor in both fishes, followed at a greater distance by the factor seasonality. The parasite communities exhibited temporal and spatial differences in the infection pattern in response to seasonal and locational variations.

Spatial and temporal variation of compositional, functional, and phylogenetic diversity in ectoparasite infracommunities harboured by small mammals

We studied patterns of compositional, functional, and phylogenetic α- and β-diversity in flea and gamasid mite infracommunities of small Siberian mammals, taking into account host-associated (species) and environmental (biome or sampling period) factors. We asked: (a) How do these factors and their interactions affect infracommunity diversity? (b) Does infracommunity composition, in terms of species, traits, and phylogenetic lineages, deviate from random? (c) Are species, traits, and phylogenetic lineages in infracommunities clustered or overdispersed?, and (d) Do patterns of diversity differ between the three diversity facets and/or the two ectoparasite taxa? We found that the α-diversity of infracommunities was strongly affected by host species, biome, and sampling period. The highest proportion of infracommunity diversity in both taxa was associated with the interaction between either host species and biome or host species and sampling period. Infracommunities of both taxa within, as well as between, host species, biomes, and sampling periods were characterized by the clustering of species, traits and lineages. The patterns of the effects of host species, biome, and sampling period on infracommunity diversity were congruent among the three diversity facets in both fleas and mites. We conclude that the assembly patterns in ectoparasite infracommunities mirror those characteristics of component and compound communities.

Con- and Heterospecific Shoaling Makes Invasive Guppies More Risk Taking

Invasive species are one of the greatest threats to biodiversity. Behavioral traits are recognized as key to promote individual’s survival in changing conditions. For social species being part of a group is key to carry out vital activities. Heterospecific social environments could provide exotic species with the opportunity to join groups and gain the advantages of being part of a larger population. Short latency to exit a refuge is a behavioral response that could be linked to invasion success as it increases the chances of individuals to locate food sources and other resources in novel environments. The guppy (Poecilia reticulata), a successful invader, has been found to take advantage of the presence of native species to reduce its refuge emergence latency and acquire information. The research was carried out in Mexico, we investigated the effect of heterospecific social contexts that include natives and other invasive viviparous fishes on guppies’ refuge emergence latency. We found that guppies’ emergence latency was shorter when accompanied by another guppy than when alone. Their latency was also shorter when with other invaders and when with native goodeids, but with one of the invaders (Pseudoxiphophorus bimaculatus) and with goodeids (Skiffia bilineata) latency reduction was not as high as when with conspecifics or with the invader Poecilia gracilis. Our experiment supports both the idea that already established invaders could provide benefits to new ones, and that native species also provide benefits but less than invaders. Increasing our knowledge about conspecific and heterospecific social interactions that could make an exotic species become invasive is key to assess the invasion risk of a community.

Competition from sea to mountain: Interactions and aggregation in low-diversity monogenean and endohelminth communities in twospot livebearer Pseudoxiphophorus bimaculatus (Teleostei: Poeciliidae) populations in a neotropical river

The role of interspecific interactions in structuring low-diversity helminth communities is a controversial topic in parasite ecology research. Most parasitic communities of fish are species-poor; thus, interspecific interactions are believed to be unimportant in structuring these communities.We explored the factors that might contribute to the richness and coexistence of helminth parasites of a poeciliid fish in a neotropical river.Repeatability of community structure was examined in parasitic communities among 11 populations of twospot livebearer Pseudoxiphophorus bimaculatus in the La Antigua River basin, Veracruz, Mexico. We examined the species saturation of parasitic communities and explored the patterns of species co-occurrence. We also quantified the associations between parasitic species pairs and analyzed the correlations between helminth species abundance to look for repeated patterns among the study populations.Our results suggest that interspecific competition could occur in species-poor communities, aggregation plays a role in determining local richness, and intraspecific aggregation allows the coexistence of species by reducing the overall intensity of interspecific competition.

Determinants of parasite distribution in Arctic charr populations: catchment structure versus dispersal potential

Parasite distribution patterns in lotic catchments are driven by the combined influences of unidirectional water flow and the mobility of the most mobile host. However, the importance of such drivers in catchments dominated by lentic habitats are poorly understood. We examined parasite populations of Arctic charr Salvelinus alpinus from a series of linear-connected lakes in northern Norway to assess the generality of lotic-derived catchment-scale parasite assemblage patterns. Our results demonstrated that the abundance of most parasite taxa increased from the upper to lower catchment. Allogenic taxa (piscivorous birds as final host) were present throughout the entire catchment, whereas their autogenic counterparts (charr as final hosts) demonstrated restricted distributions, thus supporting the theory that the mobility of the most mobile host determines taxa-specific parasite distribution patterns. Overall, catchment-wide parasite abundance and distribution patterns in this lentic-dominated system were in accordance with those reported for lotic systems. Additionally, our study highlighted that upper catchment regions may be inadequate reservoirs to facilitate recolonization of parasite communities in the event of downstream environmental perturbations.

Molecular data reveal high diversity ofUvulifer(Trematoda: Diplostomidae) in Middle America, with the description of a new species

Members of the genusUvuliferare distributed worldwide and infect aquatic snails and freshwater fishes as first and second intermediate hosts, respectively, and fish-eating birds (kingfishers) as definitive hosts. Metacercariae ofUvuliferspp. were collected from the fins and skin of 20 species of freshwater fishes in Mexico, Guatemala, Honduras, Nicaragua and Costa Rica, and the adults were recovered from the intestine of kingfishers in four localities of Mexico. The genetic divergence among 76 samples (64 metacercariae and 12 adults) was estimated by sequencing the 28S and 5.8S nuclear genes, as well as the internal transcribed spacers ITS1 and ITS2, and one mitochondrial gene (cox1). Maximum likelihood and Bayesian inference analyses inferred with each dataset showed a high genetic diversity within the genusUvuliferacross Middle America, revealing the existence of four genetic lineages that exhibit some level of host specificity to their second intermediate hosts. The metacercariae of lineage 1 were associated with characids and cyprinids in central and northern Mexico. Metacercariae of lineages 2 and 3 were associated with cichlids distributed widely across Middle America. The lack of adults of these lineages in kingfishers, in lineages 2 and 3, or the fact that just a few adult specimens were recovered, as in lineage 1, prevented a formal description of these species. The metacercariae of lineage 4 were found in poeciliids, across a distribution range comprising Mexico, Guatemala, Honduras and Nicaragua, and the adult was found in the green kingfisher in Mexico. The number of specimens sampled for lineage 4, for both gravid adults and metacercariae, allowed us to describe a new species,Uvulifer spinatusn. sp. We describe the new species herein and we discuss briefly the genetic diversity inUvuliferspp. and the importance of using DNA sequences to properly characterize parasite diversity.

How does host ecology influence sampling effort in parasite diversity estimates? A case study using Neotropical freshwater fishes

Accurately estimating biodiversity is fundamental to ecological understanding and prediction. Helminthes are often neglected in biodiversity estimates and when included are often underestimated. Here we examine how sampling effort affects estimates of parasite diversity in an assemblage of freshwater fish from a floodplain in Brazil. We also examine how ecological and behavioral factors influence the sampling effort necessary to accurately estimate the parasite diversity associated with a fish species. We use our dataset to suggest that host species with wide geographic distribution (i.e., long migrations), gregarious behavior (i.e., shoal), larger body size, higher population density, wide diet breadth (i.e., omnivorous), and autochthonous origin, increase the effort necessary to estimate the total diversity of parasites. However, estimating this parasitic fauna has several restrictions and limitations, due to the highly complex of the floodplain ecosystems, with non-linear and non-random responses.

Host specificity and the structure of helminth parasite communities of fishes in a Neotropical river in Mexico

In a tropical locality of Río La Antigua, Veracruz, Mexico, 11 fish species, represented by 244 individual fish from six freshwater fish families living sympatrically and synchronically, were examined for helminth parasites. A total of 36 taxa of helminths were recorded, 24 autogenic and 12 allogenic forms, including 6 monogeneans, 14 trematodes, 1 cestode, and 15 nematodes. Most helminth taxa were recovered for 10/11 of the component communities we analyzed. The results contribute empirical evidence that host specificity is an important force in the development of helminth communities of freshwater fishes. Each fish family has their own set of parasites, host species belonging to the same taxon share parasite species. High component community similarity among related host species was recorded, demonstrated by high prevalence and abundance, as well as dominance, of autogenic specialist species in each component community. Most autogenic helminth species are numerically and reproductively successful in relatively few host species. Autogenic helminths common in one host species are not common in others. Our findings give empirical support to the idea that low levels of sharing of parasites favor animal coexistence and high species richness, because large phylogenetic differences allow potentially competing animals to consume the same resources without being sensitive of another’s parasites.

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.

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.