Metazoan parasite species richness in Neotropical fishes: hotspots and the geography of biodiversity

Diversity of helminth parasites in aquatic invertebrate hosts in Latin America: how much do we know?

Helminths in aquatic invertebrate hosts have been overlooked in comparison with vertebrate hosts. Therefore, the known diversity, ecology and distribution of these host-parasite systems are very limited in terms of their taxonomic diversity, habitat and geographic regions. In this study we examined the published literature on helminth parasites of aquatic invertebrates from Latin America and the Caribbean (LAC) to identify the state of the knowledge in the region and to identify patterns of helminth diversity. Results showed that 67% of the literature is from Argentina, Mexico and Brazil. We found records for 772 host-parasite associations. Most records relate to medically or economically important hosts. Molluscs were the most studied host group with 377 helminth records (80% trematodes). The lymnaeids and planorbids were the most studied molluscs across LAC. Arthropods were the second most studied host group with 78 helminth records (trematodes 38%, cestodes 24% and nematodes 20%), with shrimps and crabs being the most studied hosts. Host species with the largest number of helminth taxa were those with a larger sampling effort through time, usually in a small country region. No large geographical-scale studies were identified. In general, the knowledge is still too scarce to allow any zoogeographical or helminth diversity generalization, as most hosts have been studied locally and the studies on invertebrate hosts in LAC are substantially uneven among countries.

Factors associated with parasite dominance in fishes from Brazil

The present study used regression models to evaluate the existence of factors that may influence the numerical parasite dominance with an epidemiological approximation. A database including 3,746 fish specimens and their respective parasites were used to evaluate the relationship between parasite dominance and biotic characteristics inherent to the studied hosts and the parasite taxa. Multivariate, classical, and mixed effects linear regression models were fitted. The calculations were performed using R software (95% CI). In the fitting of the classical multiple linear regression model, freshwater and planktivorous fish species and body length, as well as the species of the taxa Trematoda, Monogenea, and Hirudinea, were associated with parasite dominance. However, the fitting of the mixed effects model showed that the body length of the host and the species of the taxa Nematoda, Trematoda, Monogenea, Hirudinea, and Crustacea were significantly associated with parasite dominance. Studies that consider specific biological aspects of the hosts and parasites should expand the knowledge regarding factors that influence the numerical dominance of fish in Brazil. The use of a mixed model shows, once again, the importance of the appropriate use of a model correlated with the characteristics of the data to obtain consistent results.

Checklist of the helminth parasites of the genus Profundulus Hubbs, 1924 (Cyprinodontiformes, Profundulidae), an endemic family of freshwater fishes in Middle-America

From December 2012 to November 2014, 267 fish belonging to the family Profundulidae (representing nine of the 11 species of the genus Profundulus) were collected in 26 localities of Middle-America, across southern Mexico, Guatemala, and Honduras, comprising the distribution range of the genus, and analyzed for helminth parasites. Additionally, a database with all ten available published accounts of the helminth parasite fauna of this genus (the only genus within the family) was assembled. Based on both sources of information, a checklist containing all the records was compiled as a tool to address future questions in the areas of evolutionary biology, biogeography, ecology and phylogeography of this host-parasite association. The helminth parasite fauna of this fish group consists of 20 nominal species, classified in 17 genera and 14 families. It includes six species of adult digeneans, five metacercariae, two monogeneans, one adult cestode, three adult nematodes and three larval nematodes. The profundulid fishes are parasitized by a specialized group of helminth species (e.g.ParacreptotremablancoisensuSalgado-Maldonado et al. (2011b), Paracreptotremaprofundulusi Salgado-Maldonado, Caspeta-Mandujano & Martínez Ramírez, 2011, Phyllodistomumspinopapillatum Pérez-Ponce de León, Pinacho-Pinacho, Mendoza-Garfias & García-Varela, 2015, Spinitectushumbertoi Mandujano-Caspeta & Moravec, 2000, Spinitectusmariaisabelae Caspeta-Mandujano Cabañas-Carranza & Salgado-Maldonado, 2007 and Rhabdochonasalgadoi Mandujano-Caspeta & Moravec, 2000), representing the core helminth fauna that are not shared with other Middle-American fish species.

Distribution pattern of crustacean ectoparasites of freshwater fish from Brazil

The purpose of this study was to use the informations relating to parasite crustaceans species that was published over the course of one century (1913 to 2013), in order to search for infestation and distribution patterns among these ectoparasites in Brazilian freshwater fish species. This search was carried out on 445 samples of 119 host fish of 27 families within the orders Characiformes, Perciformes, Clupeiformes, Mugiliformes, Osteoglossiformes, Symbranchiformes, Tetraodontiformes and Siluriformes from various regions of Brazil. We organized different host-parasite systems into matrices grouping species at different taxonomic and infestation levels and according to host parameters. Five families of parasites (Ergasilidae, Argulidae, Lernaeidae, Lernaeopodidae and Cymothoidae) distributed into 76 species of 27 genera were analyzed in the host samples, which presented dominance of Ergasilidae species, mainly from the genus Ergasilus. Some crustaceans are host and site-specific, especially in relation to fish in particular habitats and lifestyles (e.g. Perulernaea gamitanae, Anphira branchialis and Riggia paranensis), while other parasites frequently have no preference (e.g. Lernaea cyprinacea and Braga patagonica). We found broadly similar distribution patterns for some crustacean species among the different localities, whereas other species showed well-defined geographical patterns, and these findings were discussed.

Molecular phylogeny of Neotropical monogeneans (Platyhelminthes: Monogenea) from catfishes (Siluriformes)

BACKGROUND

The phylogenetic relationships of dactylogyrids (Monogenea: Dactylogyridae) parasitising catfishes (Siluriformes) from the Neotropical region were investigated for the first time.

METHODS

Partial sequences of the 28S rRNA gene of 40 specimens representing 25 dactylogyrid species were analysed together with sequences from GenBank using Bayesian inference, Maximum likelihood and Parsimony methods. Monophyly of dactylogyrids infecting catfishes and the Ancyrocephalinae was evaluated using the Approximately Unbiased test.

RESULTS

The Ancyrocephalinae is a paraphyletic group of species clustering in three main clades as follows: (i) clade A comprising freshwater dactylogyrids from the Holarctic parasitising perciforms clustering together with species (Ameloblastella, Unibarra and Vancleaveus) parasitising Neotropical catfishes; (ii) clade B including species of Dactylogyrus (Dactylogyrinae) and Pseudodactylogyrus (Pseudodactylogyrinae) along with Ancyrocephalus mogurndae, and marine dactylogyrids with cosmopolitan distribution, parasites of scorpaeniforms and perciforms, along with the freshwater Cichlidogyrus and Scutogyrus (infecting African cichlids [Cichlidae]) and (iii) clade C containing exclusively dactylogyrids of siluriforms, freshwater and marine, with Palaearctic, Ethiopian, Oriental and Neotropical distributions; species of Aphanoblastella and Dactylogyridae gen. sp. 4 from the Neotropical region clustering together with species allocated in the Ancylodiscoidinae, along with species of Cosmetocleithrum, Demidospermus and Dactylogyridae gen. spp.

CONCLUSIONS

The position of the Ancylodiscoidinae within a larger clade of dactylogyrids (ancyrocephalines) indicates that this subfamily does not represent a natural group. Instead, species allocated to this clade (dactylogyrids of siluriforms along with species of the Ancylodiscoidinae) should be considered as a separate subfamily within the Dactylogyridae. The erection of this taxon requires the search for morphological diagnostic characters in addition to phylogenetic information. A similar strategy should be considered for a new classification of the paraphyletic Ancyrocephalinae. Members of the three clades do not seem to share obvious morphological synapomorphies nor clear patterns in host-parasite associations, zoogeographical distribution or ecology. Clade A should be considered as the Ancyrocephalinae sensu stricto since it includes the type species Ancyrocephalus paradoxus Creplin, 1839. A new subfamily should be proposed to accommodate species currently allocated to Ancyrocephalinae clustering within clade B. Future attempts to propose a new classification of the subfamilies in the Dactylogyridae should include the phylogenetically diverse Neotropical dactylogyrids.

Occurrence of Clavellisa ilishae (Copepoda: Lernaeopodidae) parasitizing herrings (Actinopterygii: Clupeidae) in Brazil

The lernaeopodids are highly specialized copepods which are widely distributed worldwide. In this paper the first record of Clavellisa ilishae Pillai, 1962 in the Neotropical region is documented parasitizing Sardinella brasiliensis from coastal zone of Rio de Janeiro, Brasil.

Taxonomic distinctness and richness of helminth parasite assemblages of freshwater fishes in Mexican hydrological basins

In this paper, we analyse the distributional patterns of adult helminth parasites of freshwater fishes with respect to the main hydrological basins of Mexico. We use the taxonomic distinctness and the variation in taxonomic distinctness to explore patterns of parasite diversity and how these patterns change between zoogeographical regions. We address questions about the factors that determine the variation of observed diversity of helminths between basins. We also investigate patterns of richness, taxonomic distinctness and distance decay of similarity amongst basins. Our analyses suggest that the evolution of the fauna of helminth parasites in Mexico is mostly dominated by independent host colonization events and that intra - host speciation could be a minor factor explaining the origin of this diversity. This paper points out a clear separation between the helminth faunas of northern - nearctic and southern - neotropical components in Mexican continental waters, suggesting the availability of two distinct taxonomic pools of parasites in Mexican drainage basins. Data identifies Mexican drainage basins as unities inhabited by freshwater fishes, hosting a mixture of neotropical and nearctic species, in addition, data confirms neotropical and neartic basins/helminth faunas. The neotropical basins of Mexico are host to a richest and more diversified helminth fauna, including more families, genera and species, compared to the less rich and less diverse helminth fauna in the nearctic basins. The present analysis confirms distance - decay as one of the important factors contributing to the patterns of diversity observed. The hypothesis that helminth diversity could be explained by the ichthyological diversity of the basin received no support from present analysis.

First report of austrodiplostomum compactum and ithyoclinostomum dimorphum in trahira (hoplias malabaricus) from the middle course of the Rio Doce, Minas Gerais, Brazil

Austrodiplostomum compactum and Ithyoclinostomum dimorphum are two trematodes commonly found in trahira, but these parasites were never reported in trahiras from Rio Doce. Thus, the aim of this study is to describe the occurrence of A. compactum and I. dimorphum metacercariae in trahira from the middle course of the Rio Doce and to record the presence of eggs in I. dimorphum metacercariae. The parasites were identified and analyzed using methods described previously. There were found 10 A. compactum metacercariae in the aqueous humor of eyes in four of the trahiras and 12 I. dimorphum metacercariae encysted in the peritoneal cavity in five of the trahiras. Maceration of the I. dimorphum metacercariae revealed the presence of eggs. These results demonstrate the broad distribution of these parasites and the first report of these parasites in trahira from Rio Doce.

Variation in the parasite community of the sardine fishTriportheus nematurus(Actinopterygii: Characidae) from the Medalha lagoon in the Pantanal wetland, Brazil

In July 2009 and July 2010 (two dry periods separated by an atypically large flood in the Pantanal wetland of Brazil), 34 and 33 specimens of the sardine fishTriportheus nematuruswere collected, respectively, for the study of the metazoan parasite community of this species. Parasite ecological and community descriptors were calculated for both host samples, and possible similarities were tested statistically. Five species of metazoan parasites were identified, four of which were common to both host samples. A total of 61 metazoan parasites were collected from all fish hosts (17 specimens in July 2009 (mean: 0.5 ± 0.66 parasites/fish) and 44 specimens in July 2010 (mean: 1.33 ± 1.41 parasites/fish)). The nematodeProcamallanus hilariiand the monogeneanAnacanthorussp. were the most prevalent and abundant species in 2009 and 2010, respectively. The mean total abundance and species richness were significantly higher in 2010. Parasite communities in both samples ofT. nematuruswere characterized by species with low prevalence, abundance, mean total abundance and species richness, thus indicating low parasite diversity. Significant differences in the prevalence and abundance ofP. hilariiandAnacanthorussp. between the two samples allowed the discrimination of infracommunities, which were united in two distinct groups. This appears to be the first evidence that the peculiar hydrological dynamics of the southern Pantanal wetland (Brazil) exert an important influence over the structure of the parasite community.

Patterns of distribution of the helminth parasites of freshwater fishes of Mexico

In order to draw patterns in helminth parasite composition and species richness in Mexican freshwater fishes we analyse a presence-absence matrix representing every species of adult helminth parasites of freshwater fishes from 23 Mexican hydrological basins. We examine the distributional patterns of the helminth parasites with regard to the main hydrological basins of the country, and in doing so we identify areas of high diversity and point out the biotic similarities and differences among drainage basins. Our dataset allows us to evaluate the relationships among drainage basins in terms of helminth diversity. This paper shows that the helminth fauna of freshwater fishes of Mexico can characterise hydrological basins the same way as fish families do, and that the basins of south-eastern Mexico are home to a rich, predominantly Neotropical, helminth fauna whereas the basins of the Mexican Highland Plateau and the Nearctic area of Mexico harbour a less diverse Nearctic fauna, following the same pattern of distribution of their fish host families. The composition of the helminth fauna of each particular basin depends on the structure of the fish community rather than on the limnological characteristics and geographical position of the basin itself. This work shows distance decay of similarity and a clear linkage between host and parasite distributions.

Patterns of variation in parasite component communities and infracommunities of a littoral fish species from the northern coast of Chile

The structure and similarity of the parasite communities of fish can be evaluated at the component community (CC) and infracommunity (IC) levels. Both hierarchical levels have been used to assess parasite variations in fish at large (biogeographic) scales. However, studies evaluating the consistency between these two hierarchical levels at smaller geographical scales are scarce. In this study, the parasite assemblages of 124 Paralabrax humeralis collected by local fishermen by spear fishing at four sites (El Fierro, EF; P. Angamos, PA; Santa María, ISM; San Jorge, BSJ) in northern Chile were compared to assess the variability (or similarity) of their CCs and ICs at a limited geographical scale using multivariate analysis. At the IC level, discriminant analyses showed that P. humeralis parasite communities varied significantly among sites; 70% of ectoparasite ICs were correctly assigned to each site, but only 55% of helminth parasite ICs were correctly classified. At the CC level, the composition of parasite communities as assessed by correspondence analyses varied significantly between sites. Tagia sp., Neobenedenia sp. and Philometra sp. were associated with BSJ, ISM and PA, respectively; Corynosoma sp. and most digeneans were associated with both ISM and EF. Analysis of similarities (ANOSIM) showed significant variations in the degree of similarity between P. humeralis CCs from different sites, but not between ICs. Variations between CCs from different sites reflect fish population processes (e.g., population age, reproductive segregation) and the particular conditions of their respective habitats, whereas ICs reflect individual host movements. This study demonstrated that, when examined at a limited geographical scale, IC is better than CC at capturing the local pool of parasite assemblages when host populations are spatially segregated. Therefore, in this study, it is demonstrated that at a small geographic scale, CC variations are not reflected by IC, when host population is spatially segregated.

Ontogenetic changes in heterogeneity of parasite communities of fish: disentangling the relative role of compositional versus abundance variability

In order to determine how much of the variability in parasite assemblages is driven by differences in composition or in abundance we used multivariate dispersions (average distance from infracommunities to their size class centroid in the multivariate space) as a measurement ofβ-diversity in infracommunities ofConger orbignianus, applying a set of dissimilarity measures with different degrees of emphasis on composition versus relative abundance information. To evaluate comparatively the rate of such changes, we also analysed the effect of host size by regressing differences inβ-diversity among size classes against differences in mean fish size. Multivariate dispersions varied along an ontogenetic gradient, its significance depending on the measurement used. Larger fish showed higher richness and abundance; however, smaller fish displayed lower variations in abundance but higher in composition. This could be caused by stochastic encounters at low densities due to the overdispersion of parasites in previous hosts. As fish grow, the composition of their parasite assemblages becomes homogenized by repeated exposure, with abundance thus arising as the main source of variability. Both variables act at different rates, with the exponential decay in the compositional variability as differences in fish size increase being about twice as steep as the decay in abundance variability, indicating that compositional homogeneity is reached faster than abundance heterogeneity as fish grow. Discerning between both variables is crucial in order to understand how community structure is formed by size-dependent variability of host populations.

An annotated list of fish parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda, Nematoda) collected from Snappers and Bream (Lutjanidae, Nemipteridae, Caesionidae) in New Caledonia confirms high parasite biodiversity on coral reef fish

BACKGROUND

Coral reefs are areas of maximum biodiversity, but the parasites of coral reef fishes, and especially their species richness, are not well known. Over an 8-year period, parasites were collected from 24 species of Lutjanidae, Nemipteridae and Caesionidae off New Caledonia, South Pacific.

RESULTS

Host-parasite and parasite-host lists are provided, with a total of 207 host-parasite combinations and 58 parasite species identified at the species level, with 27 new host records. Results are presented for isopods, copepods, monogeneans, digeneans, cestodes and nematodes. When results are restricted to well-sampled reef fish species (sample size > 30), the number of host-parasite combinations is 20-25 per fish species, and the number of parasites identified at the species level is 9-13 per fish species. Lutjanids include reef-associated fish and deeper sea fish from the outer slopes of the coral reef: fish from both milieus were compared. Surprisingly, parasite biodiversity was higher in deeper sea fish than in reef fish (host-parasite combinations: 12.50 vs 10.13, number of species per fish 3.75 vs 3.00); however, we identified four biases which diminish the validity of this comparison. Finally, these results and previously published results allow us to propose a generalization of parasite biodiversity for four major families of reef-associated fishes (Lutjanidae, Nemipteridae, Serranidae and Lethrinidae): well-sampled fish have a mean of 20 host-parasite combinations per fish species, and the number of parasites identified at the species level is 10 per fish species.

CONCLUSIONS

Since all precautions have been taken to minimize taxon numbers, it is safe to affirm than the number of fish parasites is at least ten times the number of fish species in coral reefs, for species of similar size or larger than the species in the four families studied; this is a major improvement to our estimate of biodiversity in coral reefs. Our results suggest that extinction of a coral reef fish species would eventually result in the coextinction of at least ten species of parasites.

A new species of Caligus (Copepoda, Siphonostomatoida) from the plankton of the Caribbean coast of Venezuela with a key to species

During a survey of the zooplankton community of Bahía Amuay, Venezuelan Caribbean, specimens of an undescribed species of Caligus Müller were collected. It resembles Caligus xystercus Cressey and Caligus ocyurus Cressey, both known only from the Caribbean Sea. The new species can be distinguished from these and other congeners by a combination of characters including the armature of legs 1 and 4, but mainly by its unique female genital complex. This is the first species of Caligus described from Venezuela. The species is described in full and a key to the species of the genus recorded in Venezuela is provided.

Parasite diversity in Oxydoras niger (Osteichthyes: Doradidae) from the basin of Solimões River, Amazonas state, Brazil, and the relationship between monogenoidean and condition factor

This study describes the parasitic fauna of Oxydoras niger from the Coari Lake, tributary of the medium Solimões River, State of Amazonas, Brazil, and the relationship between the number of Monogenoidea and the condition factor. From a total of 27 examined fish, 70.3% were parasitised by at least one parasite species as follows: Ichthyophthirius multifiliis (Protozoa), Chilodonella sp. (Protozoa), Cosmetocleithrum gussevi, C. confusus, C. parvum and Cosmetocleithrum sp. (Monogenoidea), Paracavisona impudica (Acanthocephala), Cucullanus grandistomis (Nematoda), Proteocephalus kuyukuyu (Cestoda) and Dadaytrema sp. (Digenea). Monogenoidea helminthes were the most prevalent parasite when compared to protozoan and intestinal helminthes. This study showed that O. niger has a great parasite diversity composed mainly of monogenoideans followed by acanthocephalan and digenean. This is the first record of Dadaytrema in O. niger from the Brazilian Amazon. There was a positive correlation between the number of monogenoideans and the condition factor (Kn) of fish, and with this mean intensity of infection, fish welfare was not affected.

An annotated list of parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda and Nematoda) collected in groupers (Serranidae, Epinephelinae) in New Caledonia emphasizes parasite biodiversity in coral reef fish

Abstract: Over a 7-year period, parasites have been collected from 28 species of groupers (Serranidae, Epinephelinae) in the waters off New Caledonia. Host-parasite and parasite-host lists are provided, with a total of 337 host-parasite combinations, including 146 parasite identifications at the species level. Results are included for isopods (5 species), copepods (19), monogeneans (56), digeneans (28), cestodes (12), and nematodes (12). When results are restricted to those 14 fish species for which more than five specimens were examined and to parasites identified at the species level, 109 host-parasite combinations were recorded, with 63 different species, of which monogeneans account for half (32 species), and an average of 4.5 parasite species per fish species. Digenean records were compared for 16 fish species shared with the study of Cribb et al. (2002); based on a total of 90 parasite records identified at the species level, New Caledonia has 17 new records and only seven species were already known from other locations. We hypothesize that the present results represent only a small part of the actual biodiversity, and we predict a biodiversity of 10 different parasite species and 30 host-parasite combinations per serranid. A comparison with a study on Heron Island (Queensland, Australia) by Lester and Sewell (1989) was attempted: of the four species of fish in common and in a total of 91 host-parasite combinations, only six parasites identified at the species level were shared. This suggests strongly that insufficient sampling impairs proper biogeographical or ecological comparisons. Probably only 3% of the parasite species of coral reef fish are already known in New Caledonia.

Similarity in parasite communities of the teleost fish Pinguipes brasilianus in the southwestern Atlantic: infracommunities as a tool to detect geographical patterns

Patterns of distance decay in similarity among communities of the fish Pinguipes brasilianus (Teleostei: Pinguipedidae) from five areas in the southwestern Atlantic were investigated to determine whether the rate of decay varied depending on the community level or the parasite guild analyzed (ectoparasites, adult endoparasites and larval endoparasites). Similarities in species composition were computed at both the component community and infracommunity levels. Similarity indices were calculated between all possible pairs of assemblages from different zones. Infracommunity similarity values between and within host populations were averaged. Significance of linear regressions for similarity values against distance was assessed using randomization tests. Different patterns were observed for each guild, and similarity among infracommunities within host populations varied accordingly. Decay in similarity over distance was recorded for most communities. The slopes differed significantly between infracommunities and component communities in all cases, and stronger decay was always observed for infracommunities. Different geographical patterns in parasite communities were a consequence of variability in parasite availability in the different regions, modulated by oceanographic conditions, as well as variation among species in terms of host specificity and life-cycles strategies. Infracommunities showed a stronger effect of distance than component communities, probably due to the influence of short term and local variability of oceanographic conditions.

Helminth species diversity of mammals: parasite species richness is a host species attribute

Studies investigating parasite diversity have shown substantial geographical variation in parasite species richness. Most of these studies have, however, adopted a local scale approach, which may have masked more general patterns. Recent studies have shown that ectoparasite species richness in mammals seems highly repeatable among populations of the same mammal host species at a regional scale. In light of these new studies we have reinvestigated the case of parasitic helminths by using a large data set of parasites from mammal populations in 3 continents. We collected homogeneous data and demonstrated that helminth species richness is highly repeatable in mammals at a regional scale. Our results highlight the strong influence of host identity in parasite species richness and call for future research linking helminth species found in a given host to its ecology, immune defences and potential energetic trade-offs.