Species of Dactylogyridae (Monogenoidea, Polyonchoinea) from the gills of haemulid and lutjanid fishes (Perciformes) from the Pacific coast of Mexico.

Examination of the gill lamellae of the Panama grunt Rhencus panamensis (Steindachner) (Haemulidae), golden snapper Lutjanus inermis (Peters), and yellow snapper Lutjanus argentiventris (Peters) (Lutjanidae) (Perciformes) from the coast of the Guerrero State (eastern Tropical Pacific) of Mexico revealed 5 species of Monogenoidea: Euryhaliotrema disparum n. sp. on R. panamensis; Haliotrematoides uagroi n. sp. on L. inermis; and E. anecorhizion Kritsky & Mendoza-Franco, 2012, E. fastigatum (Zhukov, 1976) Kritsky & Boeger, 2002, and E. paracanthi (Zhukov, 1976) Kritsky & Boeger, 2002 on L. argentiventris. Specimens found on R. panamensis were assigned within Euryhaliotrema as a new species possessing the atypical morphology of the male copulatory organ (i.e., a coiled tube with clockwise rings). Haliotrematoides uagroi n. sp. differs from Haliotrematoides striatohamus (Zhukov, 1981) Mendoza-Franco, Reyes-Lizama & Gonzalez-Solis, 2009 from Haemulon spp. (Haemulidae) from the Caribbean Sea (Mexico) in having inner blades on the distal shafts of the ventral and dorsal anchors. The present paper represents the first finding of a species of Euryhaliotrema (E. disparum n. sp.) on a species of Rhencus and the second species on a haemulid host, and H. uagroi n. sp. as the first monogenoidean species described on L. inermis. Euryhaliotrema anecorhizion, E. fastigatum, and E. paracanthi on L. argentiventris in the Pacific coast of Mexico represent new geographical records.

Walteriella n. g. (Monogenoidea: Dactylogyridae) from the gills of pimelodid catfishes (Siluriformes: Pimelodidae) from the Peruvian Amazonia based on morphological and molecular data.

On the basis of morphological and molecular data, Walteriella n. g. is proposed to accommodate the dactylogyrid parasites Walteriella conica n. sp. (type-species) from the gills of Platynematichthys notatus (Jardine) (type-host) and Brachyplatystoma juruense (Boulenger), and Walteriella ophiocirrus n. sp. from the gills of Platystomatichthys sturio (Kner) (type-host), all fish host belonging to the Pimelodidae collected in the Peruvian Amazonia. Species of the new genus are distinguished from other dactylogyrids infecting Neotropical catfishes by the presence of a folded germarium, a male copulatory organ basally articulated to the accessory piece, a cone-shaped seminal receptacle, and ventral and dorsal bars with projections directed anteriorly. Both species of the new genus form a strongly supported lineage closely related to Dactylogyridae gen. sp. 13, a parasite of Hypophthalmus edentatus Spix & Agassiz (Pimelodidae) in an analysis of partial sequences of the 28S rRNA gene. The clade formed by species of Walteriella n. g. and Dactylogyridae gen. sp. 13 is closely related to other dactylogyrids infecting pimelodid catfishes. Based on the morphology of its haptoral elements and copulatory complex, the species Dactylogyridae gen. sp. 13 is morphologically different from species of Walteriella n. g., but its generic assignment is still unclear.

New species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 and Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986 (Monogenea: Dactylogyridae) infecting the gills of catfishes (Siluriformes) from the Peruvian Amazonia.

During a research on gill ectoparasites of siluriform fishes from the Peruvian Amazonia, the following monogeneans were found: Ameloblastella edentensis n. sp. from Hypophthalmus edentatus Spix & Agassiz; Ameloblastella peruensis n. sp. from Hypophthalmus sp.; Ameloblastella formatrium n. sp. from Pimelodidae gen. sp. (type-host) and Duopalatinus cf. peruanus Eigenmann & Allen; Ameloblastella unapioides n. sp. from Sorubim lima (Bloch & Schneider) (type-host) and Pimelodus sp; Cosmetocleithrum tortum n. sp. from Nemadoras hemipeltis (Eigenmann); and Cosmetocleithrum bifurcum n. sp. from Hassar orestis (Steindachner) (both Doradidae). All new species described herein are mainly differentiated from their congeners based on the morphology of the copulatory complex. The pimelodids H. edentatus and S. lima, and the doradids N. hemipeltis and H. orestis represent new hosts species for species of Ameloblastella Kritsky, Mendoza-Franco & Scholz, 2000 and Cosmetocleithrum Kritsky, Thatcher & Boeger, 1986, respectively. The morphological diagnosis of the present species of Ameloblastella and Cosmetocleithrum also supported by a previous molecular analysis of these species is briefly discusssed herein.

Two new species of Urocleidoides Mizelle et Price, 1964 (Monogenoidea) from the gill lamellae of profundulids and poeciliids from Central America and southern Mexico.

During investigations of gill ectoparasites (Platyhelminthes) parasitising freshwater fish from Central America (Guatemala, Honduras, El Salvador and Panama) and southeastern Mexico (Guerrero, Oaxaca and Chiapas), the following dactylogyrid monogenoidean were found: Urocleidoides simonae sp. n. from Profundulus punctatus (Günther) (type host), Profundulus balsanus Ahl, Profundulus guatemalensis (Günther), Profundulus kreiseri Matamoros, Shaefer, Hernández et Chakrabarty, Profundulus labialis (Günther), Profundulus oaxacae (Meek), Profundulus sp. 1 and Profundulus sp. 2 (all Profundulidae); Urocleidoides vaginoclaustroides sp. n. from Pseudoxiphophorus bimaculata (Heckel) (type host) and Poeciliopsis retropinna (Regan) (both Poeciliidae); and Urocleidoides vaginoclaustrum Jogunoori, Kritsky et Venkatanarasaiah, 2004 from P. labialis, Profundulus portillorum Matamoros et Shaefer and Xiphophorus hellerii Heckel (Poeciliidae). Urocleidoides simonae sp. n. differs from all other congeneric species in having anchors with well-differentiated roots, curved elongate shaft and short point. Urocleidoides vaginoclaustroides sp. n. most closely resembles U. vaginoclaustrum, but differs from this species mainly in the shape of its anchors (i.e. evenly curved shaft and short point vs curved shaft and elongate point extending just past the tip of the superficial anchor root). The complexity of potential hosts for species of Urocleidoides and their effect on its distribution on profundulid and poeciliid fishes are briefly discussed.

Inter-annual and seasonal variations of the metazoan parasite communities of the blue sea catfish Ariopsis guatemalensis (Siluriformes: Ariidae), in a tropical coastal lagoon.

Parasitological studies of long-term inter-annual variations provide more precise and reliable information about the biological structure of fish parasite communities, and constitute a reference data base for future studies. A total of 1103 blue sea catfish Ariopsis guatemalensis from a tropical eutrophic coastal lagoon were examined for parasites over a 22-year period (from May 2000 to October 2022), to test the hypothesis that parasite communities of this host, should exhibit greater variations in their structure and species composition mainly over long-term periods. Three species of monoxenous (single-host life cycle), and nine of heteroxenous (multi-host life cycle) parasites were identified. The results indicated that parasite species composition of this catfish has remained stable over a 22-years period. However, the community structure has registered notable changes over periods of several years, mainly due to the replacement of the numerically dominant species. Temporal variations in the infection dynamics of component parasite species, were possibly caused by a combination of biotic and abiotic factors, influenced by the seasonal dry/rainy cycle, which can affect the availability of intermediate host populations, as well as the feeding and reproductive behavior of the host.

Neotropical Monogenoidea. 57. Revision and phylogenetic position of Scleroductus Jara & Cone, 1989 (Gyrodactylidae), with descriptions of new species from the Guatemalan chulin Rhamdia guatemalensis (Günther) (Siluriformes: Heptapteridae) in Mexico and the barred sorubim Pseudoplatystoma fasciatum (Linnaeus) (Siluriformes: Pimelodidae) in Brazil.

The diagnosis of Scleroductus Jara & Cone, 1989 (Gyrodactylidae) is amended to include viviparous species having a large spine associated with the ejaculatory duct within the male copulatory organ, two band-like projections originating from the posterior margin of the superficial bar and hooks evenly distributed along the haptoral margins. Two new species of Scleroductus are described from the external surfaces of siluriform fishes of Mexico and Brazil: Scleroductus lyrocleithrum n. sp. from the Guatemalan chulin Rhamdia guatemalensis (Günther) (Heptapteridae) in a cenote on the Yucatan Peninsula, Mexico; and Scleroductus angularis n. sp. from the barred sorubim Pseudoplatystoma fasciatum (Linnaeus) (Pimelodidae) in the Rio Tocantins, Tocantins, Brazil. Scleroductus sp. is recorded from the jundiá Rhamdia quelen (Quoy & Gaimard) (Heptapteridae) in the Iguaçu drainage of southern Brazil. Phylogenetic analyses of 18S rDNA suggest that Scleroductus (represented in the analyses by Scleroductus sp. from R. quelen), Ieredactylus Schelkle, Paladini, Shinn, King, Johnson, van Oosterhout, Mohammed & Cable, 2011 (represented by its type-species) and Gyrodactyloides Bychowsky, 1947 (represented by G. bychowskii Al'bova, 1948) comprise the sister taxon to the remaining viviparous gyrodactylids, with Scleroductus serving as the sister group to Ieredactylus + Gyrodactyloides. The clade containing the three taxa is supported by two putative synapomorphic features: two band-like projections (R1 sclerites) originating from the posterior margin of the superficial bar and a large spine associated with the ejaculatory duct within the male copulatory organ.

New and previously known ectoparasitic monogenoids (Platyhelminthes) on native and non-native fishes from tributaries of the Usumacinta River basin (southern Mexico), a Neotropical transition zone.

During a research on morphological diversity of gill ectoparasites on native and non-native fishes from tributaries (Palizada, El Recreo and Lacantún rivers) of the Usumacinta River Basin in the states of Campeche, Tabasco, and Chiapas (southern Mexico), the following monogenoids were found: Icelanonchohaptor tropicalis n. sp. on Usumacinta buffalo Ictiobus meridionalis (Günther, 1868) (Catostomidae); Heteropriapulus simplexiodes n. sp. and Heteropriapulus heterotylioides n. sp. on catfishes Pterygoplichthys pardalis (Castelnau, 1855) (Loricariidae) (type host) and Pterygoplichthys disyunctivus (Weber, 1991); Ligictaluridus mirabilis (Mueller 1937; Klassen and Beverley-Burton1985 from the southern blue catfish Ictalurus meridionalis (Günther, 1864) (Ictaluridae); Aristocleidus mexicanus Mendoza-Franco and Vidal-Martínez, 2001 on Eugerres mexicanus (Steindachner, 1863) (Gerreidae) (all monogenoidean species in the Dactylogyridae); and Diplectanocotyla megalopis Rakotofiringa and Oliver1987 (Diplectanidae) on tarpon Megalops atlanticus Valenciennes, 1847 (Megalopidae). The new species of Icelanonchohaptor and Heteropriapulus are herein described for the first time from a native catostomid and non-native Pterygoplichthys spp., respectively. While I. tropicalis n. sp. and L. mirabilis are morphologically comparable with their congeners from the Nearctic (i.e., United States and Canada), all other monogenoids exhibited Neotropical affinities. Present study shown that the gill monogenoids on native and non-native fishes in the Neotropical Mexican transition zone of the Usumacinta River basin are equally represented by species with Nearctic and Neotropical affinities including those adapted to freshwater environment in this area from marine ancestry.

Parasitic crustaceans (Branchiura and Copepoda) parasitizing the gills of puffer fish species (Tetraodontidae) from the coast of Campeche, Gulf of Mexico.

New information on the marine parasitic crustaceans from the Campeche coast, Gulf of Mexico (GoM), can improve our baseline knowledge of the ecology of both the host and parasite by providing, for example, parameters of infection. Such knowledge is especially important for fish farming, so that appropriate quarantine measures can be established. Our aim was to morphologically identify the parasitic crustaceans infecting puffer fish of commercial importance in the coastal zone of Campeche, Mexico. We provide new information on four known species of parasitic crustaceans from 92 specimens representing five species of tetraodontid fish. The parasitic crustaceans Argulus sp. (Branchiura, Argulidae), Caligushaemulonis (Caligidae), Pseudochondracanthusdiceraus (Chondracanthidae), and Taeniacanthuslagocephali (Taeniacanthidae) (all Copepoda) were found on Lagocephaluslaevigatus, Sphoeroidesnephelus, S.parvus, S.spengleri, and S.testudineus. This study revealed the occurrence of P.diceraus, which is of importance in aquaculture, on Sphoeroidesannulatus in the Mexican Pacific. Additionally, our results and other documentary records provide the first evidence of the interoceanic occurrence of the same parasitic crustacean species in the south-southwest of Gulf of Mexico, the Atlantic Ocean, and the Pacific Ocean. Moreover, our study provides valuable information on the biodiversity of parasitic crustaceans present in the GoM on puffer fish which are of great commercial importance for human consumption, fisheries, and aquaculture.

New Species of Rhabdosynochus Mizelle and Blatz 1941 (Monogenoidea: Diplectanidae) From the Gills of the Cultured Centropomus viridis (Perciformes) in the Mexican Eastern Tropical Pacific.

PURPOSE: There are currently nine monogenoidean species of Rhabdosynochus infecting the gill lamellae of wild and cultured centropomid fishes from tropical and subtropical waters of the western Atlantic and eastern Pacific Oceans. The purpose of the present study was to describe the morphological distinctiveness of two new species of Rhabdosynochus found on the cultured Centropomus viridis collected from floating cages from the Mexican eastern Tropical Pacific in 2018. METHODS: monogenoideans were fixed with 4-5% formalin solution, observed and measured as temporary or permanent mounts stained with Gomori's trichrome, and mounted in Canada balsam. Other specimens were mounted on slides using a mixture of lactic acid (LA) and glycerin-ammonium picrate (GAP) and then remounted in Canada balsam to obtain measurements of the haptoral structures and copulatory complex. Illustrations were prepared with the aid of a drawing tube using a Leica microscope DM 2500 with Nomarski interference contrast. RESULTS: Rhabdosynochus viridisi n. sp. is mainly differentiated from all other congeneric species in the shape and size of their copulatory complexes, i.e., length 75-105 µm vs. 45-55 µm in R. alterinstitus, 26-44 µm in R. volucris, 19-22 µm in R. lituparvus, 21-37 µm in R. siliquaus, 48-75 µm in R. hargisi, 37-44 µm in R. hudsoni and 44-61 µm in R. guanduensis. Rhabdosynochus pacificus n. sp. differs from all other species of the genus in having an accessory piece (one subunit) distally twisted. CONCLUSIONS: Based on the morphometric differences of the two new species described above, the number of valid species of Rhabdosynochus has now increased to 11. These two new species of Rhabdosynochus represent the first described species of the genus on C. viridis.

Helminth Communities of Anisotremus virginicus (Perciformes: Haemulidae) In Veracruz, Mexico.

A helminthological analysis was performed on 91 specimens of the porkfish, Anisotremus virginicus (Linnaeus) (Haemulidae), captured in coral reef habitats of the Parque Nacional Sistema Arrecifal Veracruzano (PNSAV) (Veracruz Reef System National Park), in Veracruz, Mexico. A total of 22 helminth taxa were recorded: 9 digeneans, 6 monogeneans, 1 cestode, 4 nematodes, and 2 acanthocephalans. From the 22 taxa, 11 are new host records and 7 are new geographic records. The highest prevalence was found for Monorchis latus Manter, 1942 (69%), and Mexicana anisotremumCezar, Paschoal and Luque, 2012 (68%), and the highest mean intensity was found for M. anisotremum (19.6), M. latus (18.9), and Dollfusentis chandleri Golvan, 1969 (10.8). Other important values were the component community richness (S = 22), diversity (Shannon index H' = 1.6), and infracommunity level (S = 3.1 ± 1.4; Brillouin index, H = 0.52 ± 0.3), which were similar to those found in other marine fish at the same study site. Our result represents a significant range extension for several helminth taxa. The parasite communities of A. virginicus rank among the richer parasite communities of neotropical marine fishes. In addition, the results reveal the PNSAV is a diverse area for the parasite assemblage of neotropical reef marine fishes, particularly of haemulids but also for other fish families.

Factors determining parasite community richness and species composition in black snook Centropomus nigrescens (Centropomidae) from coastal lagoons in Guerrero, Mexico.

Species richness and composition were determined for parasite communities in the black snook Centropomus nigrescens collected from five coastal lagoons in the Guerrero state, Mexico. A total of 354 fish were collected between December 2007 and November 2008. Twenty-four species of parasite were identified: 2 monogeneans, 12 digeneans, 4 acanthocephalans, 1 cestode, 4 nematodes, and 1 pentastomid. The communities consisted mainly of autogenic parasites, and all were dominated by the digenean Paracrytogonimus yamagutii. Community species composition was similar among lagoons, although the influence of local conditions prevented them from being identical. Host traits such as predator feeding habits, body size, and vagility contributed to parasite community structure and species composition.

Plastic density as a key factor in the presence of microplastic in the gastrointestinal tract of commercial fishes from Campeche Bay, Mexico.

Microplastics (MPs) are currently one of the primary marine pollution problems around the world. MPs are distributed throughout the water column, dependent mainly on the density that is given by the polymer type, as well as the location, depth, and velocities of the water flows. This situation allows all aquatic organisms to be exposed to MPs. Furthermore, toxic substances can adhere to the MPs, making the consumption of fish with MPs a risk to human health. The aim of this study was to evaluate and characterize the microplastics present in the gastrointestinal tract of six species of fish which had the highest human consumption in Campeche, Mexico and their relationship with the density of MPs founded. A total of 316 microplastic particles from 240 individuals were found with 1.31 ± 2.59 of microplastics per fish. The results indicate that there are differences (KW-H = 53.14) between the densities of the MPs present in demersal fish (1.41 ± 0.4 g cm-3) with respect to the pelagic species (1.04 ± 0.24 g cm-3). Likewise, differences were found between fibers, fragments, and pellets present in the studied fish with a pelagic: demersal ratio of 1: 2.4 for all microplastics. The demersal species Haemulon plumierii (n = 40) presented the highest number of MPs with 115 items in total, 73 fibers, and 42 fragments. The results of this research show the first evidence that the density of the material from which microplastics are made play a key role determining their fate in marine fish habitats.

Dataset on the diversity of helminth parasites of freshwater fish in the headwaters of the Coatzacoalcos river, in Oaxaca, Mexico.

The data presented in this article are related to the research article entitled " Diversity of helminth parasites of freshwater fish in the headwaters of the Coatzacoalcos river, in Oaxaca, Mexico " published in International Journal for Parasitolology: Parasites and Wildlife. This dataset document the diversity of helminth parasites found in 25 fish species from 8 families from rivers in the headwaters of the Coatzacoalcos river basin at the border between Oaxaca and Veracruz states, Isthmus of Tehuantepec zone, southeastern Mexico, in the northernmost end of Central America. We record here 48 species, 44 genera and 29 helminth families. Most of the helminth species recorded in this area has also been collected from Central American bodies of freshwater south of Mexico. The material in this Data in Brief paper comprised the raw data on the abundance distribution of each helminth taxa recorded in each of the host and location; i. e. the number of helminth individuals of each helminth taxa found in each one individual fish from each species from each of the localities sampled. The data set is contained in one text-table matrix per fish-host, date of collection and locality of helminth taxa (lines) per fish host species (columns).

Diversity of helminth parasites of freshwater fish in the headwaters of the Coatzacoalcos River, in Oaxaca, Mexico.

We documented the diversity of helminth parasites of 25 fish species from 8 families occurring in the headwaters of the Coatzacoalcos river basin. This river flows along the border between the states of Oaxaca and Veracruz, in the region of the Isthmus of Tehuantepec, in south-eastern Mexico, and in northern Central America. We recorded 48 species, representing 44 genera and 29 helminth families. Six of the 25 fish species were examined for helminths for the first time; 60 new host records were reported. Nematodes and trematodes were the most abundant taxonomic groups. The helminth fauna from our study area consists of primarily central American species. Most species recorded from this area have also been captured from freshwater bodies between the Isthmus of Tehuantepec and the Isthmus of Panama. However, three species, including an acanthocephalan and two nematodes, are likely endemic to this area. We argue that, in contrast to the presence of larval helminths, which mostly depends on the geographical location of water bodies, adult helminths are an integral and consistent component of the regional community. Data on taxonomic composition and distribution of helminth fauna reported in this paper, contribute to a better understanding of this faunal component in northern Central America (CA). Furthermore, knowledge of helminth parasites of freshwater fish from Neotropical Mexico and CA facilitates prediction of which parasite species is likely to infect fish in a specific geographical area.

Data from monogenean and endohelminth communities in twospot livebearer Pseudoxiphophorus bimaculatus (Teleostei: Poeciliidae) populations in a neotropical river.

The data presented in this article are related to the research article entitled "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." accepted for publication in Ecology and Evolution. The data describes the communities of helminth parasites in 11 populations of a small poeciliid freshwater fish Pseudoxiphophorus bimaculatus (Heckel, 1848) sampled along the La Antigua river basin in Veracruz, Mexico. We examined 19 P bimaculatus from one locality, 21 from another locality, and 20 from each of the other nine locations sampled in June 2016. A total of 220 individual fish were examined, and in this paper we provide the data for 18 helminth parasite taxa recorded from them. The material in this Data paper comprised the raw data on the abundance, i.e. the number of helminth individuals of each of 18 taxa found in each one individual of P. bimaculatus from each of 11 localities. The data set is contained in a single text-table including one matrix containing each of the 220 host P. bimaculatus examined from 11 localities (lines). Measures for each host P. bimaculatus include total length, standard length, maximum deep and sex, documented for everyone fish examined, plus data of the number of individual helminth of each taxa collected by each examined fish are placed in the columns. These data might be used to examine spatial distribution of helminth parasite taxa. These data might be reused to examine the spatial variation in community structure of helminth parasites of freshwater fish. This kind of data could be used to provide an assessment of human environmental impacts, or for public awareness of conservation objectives.

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.

Dactylogyrids (Monogenoidea) parasitizing the gills of Astyanax spp. (Characidae) from Panama and southeast Mexico, a new species of Diaphorocleidus and a proposal for Characithecium N. Gen.

Diaphorocleidus orthodusus n. sp. and Diaphorocleidus kabatai (Molnar, Hanek and Fernando, 1974) Jogunoori, Kritsky, and Venkatanarasaiah, 2004 are detailed from Astyanax orthodus and Astyanax aeneus, respectively. Palombitrema heteroancistrium (Price and Bussing, 1968) is described from specimens collected from A. aeneus, and Urocleidoides strombicirrus (Price and Bussing, 1967) is reported for the first time from A. aeneus and Astyanax fasciatus in Panama. Characithecium costaricensis (Price and Bussing, 1967) n. comb. is detailed based on specimens from A. aeneus. Characithecium costaricensis is characterized by having overlapping gonads, a medioventral vaginal aperture, a copulatory complex consisting of single counterclockwise coil of the copulatory organ that is articulated to the accessory piece, and a haptor having 2 pairs of anchors, dorsal and ventral bars, and 14 hooks. Measurements of body size varied substantially among individual worms, both within and across different host species and locations. However, the morphological differences were insufficient to separate species of Characithecium. This result suggests limited parasite speciation across sympatric species of Astyanax in Mexico and Panama.

Interoceanic occurrence of species of Aristocleidus Mueller, 1936 (Monogenoidea: Dactylogyridae) parasitizing the gills of gerreid fishes in the Neotropics.

During investigations of fish parasites in the Neotropics (including the state of Veracruz and the Yucatán Peninsula in the Gulf of Mexico, the Chautengo Lagoon on the Pacific coast of the state of Guerrero in Mexico, and Lake Gatun in the Panama Canal), three monogenoidean (Dactylogyridae) species were found parasitizing the gills of gerreids (Gerreidae): Aristocleidus hastatus Mueller, 1936, was recovered from Eugerres plumieri (Cuvier) and Diapterus auratus Ranzani in Veracruz, from D. auratus and Diapterus rhombeus (Cuvier) in Yucatán, from Eugerres brasilianus (Cuvier) in Panama (all new hosts and geographical records), and from D. peruvianus (Cuvier) and Gerres cinereus (Walbaum) in Guerrero; Aristocleidus lamothei Kritsky and Mendoza-Franco, 2008, was recovered from E. plumieri in Veracruz and from D. rhombeus in Yucatan (new hosts and geographical records), and Aristocleidus sp. was recovered from G. cinereus in Guerrero. Results from this study suggest that species of Aristocleidus exhibit wide host specificity within gerreid fishes and that geminate species within this parasite genus may have originated with the formation of the Isthmus of Panama (3.1 to 3.5 ma). Evidence is also presented suggesting the potential role of the Panama Canal as a passageway allowing the interoceanic dispersal of Aristocleidus species across the isthmus.

Revision of the amphiamerican Neotetraonchus Bravo-Hollis, 1968 (Monogenoidea: Dactylogyridae), with a description of N. vegrandis n. sp. from the gill lamellae of the blue sea catfish Ariopsis guatemalensis (Siluriformes: Ariidae) off the Pacific Coast of Mexico.

Neotetraonchus Bravo-Hollis, 1968 is revised and reassigned to the Dactylogyridae Bychowsky, 1933 based on examinations of specimens representing four species from the gill lamellae of sea catfishes (Ariidae). The monotypic Neotetraonchidae Bravo-Hollis, 1968 is placed in synonymy with the Dactylogyridae. Neotetraonchus bychowskyi Bravo-Hollis, 1968 (type-species), is redescribed from the tete sea catfish Ariopsis seemanni (Günther) (type-host) in the eastern Pacific Ocean off Panama (new geographical record). Neotetraonchus vegrandis n. sp. is described from the blue sea catfish A. guatemalensis (Günther) off the Pacific Coast of Mexico. Neotetraonchus bravohollisae Paperna, 1977 is redescribed from the hardhead sea catfish A. felis (L.) in the Gulf of Mexico off the Yucatan Peninsula. Neotetraonchus felis (Hargis, 1955) Paperna, 1977 is redescribed from A. felis in the Gulf of Mexico off Mississippi and the Yucatan Peninsula (new geographical record). Morphological similarities between species of Neotetraonchus suggest the likely presence of geminate species pairs flanking the Isthmus of Panama.

Aggregation and negative interactions in low-diversity and unsaturated monogenean (Platyhelminthes) communities in Astyanax aeneus (Teleostei) populations in a neotropical river of Mexico.

We studied monogenean communities of 11 populations of Astyanax aeneus (Günther) separated by small geographical distances along 60 km of the Lacantún river in Chiapas, Mexico, in February and August 2012. We found 12 monogenean taxa. Amongst these, five species specialist for Astyanax were widely distributed regionally, constituting 90% of the total collected monogeneans, with one of these species dominating most component communities. The high similarities in terms of composition between the component communities (SJaccard > 60%) as well as in terms of the abundance and composition between infracommunities (SBray Curtis > 40%), provide empirical evidence that transmission, both between hosts at the same location and between component communities, is high and effective. No resemblance pattern was detected between locations in terms of their spatial distribution. The composition of these communities was spatially and temporally consistent over the two very different weather periods sampled. These communities were not saturated. Our analysis suggests that the potential richness of the infracommunities is proportional to the number of monogenean species available in the component community. We found aggregation in the populations and between monogenean species. Intraspecific aggregation is density dependent, suggesting that intraspecific competition for space is not a limiting factor for the development of the population. We evaluated the associations for each species pair and detected 77% negative interactions (134/177 associations), suggesting that interspecific competition plays an important role in shaping these communities. The negative correlations of abundance between pairs of species contributes to confirmation of competition. Intraspecific aggregation increased relative to interspecific aggregation with richness in the component community, facilitating coexistence of the species. Our results suggest that these are interactive communities, where monogeneans disperse efficiently from a common source, colonize patches (hosts) together, and compete with other species even at low population densities. Finally, the coexistence of these species is favored by the unpredictable recruitment and aggregated use of fragmented resources.