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The Neotropical region hosts 4225 freshwater fish species, ranking first among the world's most diverse regions for freshwater fishes. Our NEOTROPICAL FRESHWATER FISHES data set is the first to produce a large-scale Neotropical freshwater fish inventory, covering the entire Neotropical region from Mexico and the Caribbean in the north to the southern limits in Argentina, Paraguay, Chile, and Uruguay. We compiled 185,787 distribution records, with unique georeferenced coordinates, for the 4225 species, represented by occurrence and abundance data. The number of species for the most numerous orders are as follows: Characiformes (1289), Siluriformes (1384), Cichliformes (354), Cyprinodontiformes (245), and Gymnotiformes (135). The most recorded species was the characid Astyanax fasciatus (4696 records). We registered 116,802 distribution records for native species, compared to 1802 distribution records for nonnative species. The main aim of the NEOTROPICAL FRESHWATER FISHES data set was to make these occurrence and abundance data accessible for international researchers to develop ecological and macroecological studies, from local to regional scales, with focal fish species, families, or orders. We anticipate that the NEOTROPICAL FRESHWATER FISHES data set will be valuable for studies on a wide range of ecological processes, such as trophic cascades, fishery pressure, the effects of habitat loss and fragmentation, and the impacts of species invasion and climate change. There are no copyright restrictions on the data, and please cite this data paper when using the data in publications.

Antecedentes: La interconexion lateral en el sistema rio-llanura de inundacion Maluco fue reducida parcialmente por una carretera construida sobre una barrera natural. Objetivo: Determinar si las concentraciones de clorofila-a (Cla-a) y nutrientes contrastan en diferentes niveles de agua (NA) durante un ano hidrologico en el humedal fluvial. Metodos: El NA, Cla-a y nutrientes (NO2-, NO3-, NH4+ y PT) se midieron simultaneamente seis veces en dos estaciones durante dos anos. Las diferencias esperadas de las concentraciones de Cla-a y nutrientes, relacionadas a la fluctuacion intra-anual del NA, fueron analizadas por medio de tecnicas multivariadas. La hipotesis sostiene que no se detectaran diferencias intra anuales de Cla-a y nutrientes debido a la reduccion de la interconexion lateral por el efecto fisico del terraplen. Resultados: Ninguna variable fue descartada con el ACP. La distribucion intra-anual de las muestras resulto similar segun la rutina de perfiles de similitud. Coincidentemente: 1) mas del 54% de los valores de Cla-a y PT indicaron condiciones hipereutroficas durante todo el ano y 2) ninguno de los valores de WL sobrepaso la altura del terraplen (4.5 msnm). Ademas, las concentraciones maximas de Cla-a se registraron en los WL minimos. Conclusiones: La similitud intra-anual de la Cla-a y los nutrientes inorganicos se puede vincular a que la llanura de inundacion estuvo desconectada del rio Grijalva, ya que la inundacion no sobrepaso la altura del terraplen durante todo el tiempo de muestreo. La tendencia intra-anual independiente al tiempo de la persistencia de las altas concentraciones de Cla-a y PT en el sistema rio llanura de inundacion abre la oportunidad de estimar el caudal de entrada minimo requerido para restaurar los procesos biogeoquimicos en un estudio a largo plazo.

Hypanus sabinus is reported in the limnetic environments in the coastal plain of the Southern Gulf of Mexico. Eight specimens were collected 51 km away from the coastline in electric conductivity values less than 1,017 µS cm-1. One pregnant female and one male with two caudal spines are included. These findings represent the first limnetic records of this species in southern Mexico.

Background. The distribution and diet of fish, as well as the specific composition of their prey, have been affected by the magnification of the spatial variations in salinity due to hydraulic infrastructure and climate change. Cathorops aguadulce was selected based on previous records of its diet and its current dominance in the estuarine systems in the southern Gulf of Mexico. Goals . The feeding habits were evaluated in relation to the variation of size composition, day-night, and seasonality in a coastal lagoon in the southern Gulf of Mexico. Methods. Two hundred ten digestive tracts were analyzed in juveniles and adults captured in a sampling that included the day-night and seasonal variation in three sampling sites located in a salinity gradient. The size composition was correlated (Spearman coefficient) with the spatial and temporal variation of salinity and temperature. The temporal and spatial variations of the Repletion (IR) and Relative Importance (IIR) indexes were analyzed using Kruskal-Wallis test and hierarchical clustering. Results. The size composition was independent of salinity variation and IR values (Kruskal-Wallis; p =0.649). Yet diet intensity in the dry season was significantly greater than in the transition and rainy seasons (Kruskal-Wallis; p =0.00001). Among the 11 food items defined, animal detritus and malacostracans, mainly tanaids, were the dominant feeding categories in the frequency of occurrence and according to the IIR. However, detritus predominated in juveniles, while tanaids were the preponderant item in the adults. Conclusions. Even though laguna Mecoacan recorded an ample salinity variation, C. aguadulce recorded a significant temporal variation in intensity of diet; the ontogenic shift of its diet was more relevant than the effects of the environmental variation of its feeding habits. This conclusion opens the possibility of testing whether the ontogenetic variation of their functional morphological traits is associated with the acquisition of food or movement.

En Mexico existen 3,256 especies de fitoplancton reportadas. En la region sureste, particularmente en las cuencas de los rios Tonala y Grijalva-Usumacinta, el registro varia entre 155 y 300 especies. Este numero de especies se considera bajo para una de las cuencas con mayor reserva de agua en el pais. Por tal motivo, se planteo el objetivo de reportar las especies de fitoplancton presentes en el humedal tropical Chaschoc, ubicado en la cuenca del rio Usumacinta. Para ello, el fitoplancton se recolecto durante el flujo bajo del ciclo de inundacion en 2014 mediante arrastres oblicuos. Se registraron 129 morfoespecies de 6 grupos taxonomicos: Cyanophyta (Cyanoprocaryota), Bacillariophyta, Chlorophyta, Cryptophyta, Euglenophyta (Euglenozoa) y Dinophyta (Dinoflagellata). Entre estos, las Chlorophyta fueron el grupo mejor representado, mientras que las Cryptophyta resultaron el grupo con menos especies. En la lista floristica se reportan 40 nuevos registros para la cuenca baja del rio Usumacinta, 13 especies potencialmente toxicas y 42 indicadoras de contaminacion por materia organica o eutrofizacion. Sin embargo, es esperable que el registro de especies aumente con muestreos en las diferentes temporadas del ciclo hidrologico y otros humedales asociados con el rio Usumacinta y sus tributarios.

To distinguish between the stress of Vallisneria americana caused by increases either in the molar N:P relation (N-NO3 and P-H2PO4) or in the concentration of nutrients (CN), the nutritional regimen (NR) was examined by means of two randomized factorial experiments on plants cultured in vitro in modified MS medium. The first (RN1) crossed N:P relation of 16, 20, and 24 and CN (%) of 25, 50, and 100; while the second (RN2) evaluated N:P relations of 48, 60, 72, and CN percentages of 3.125, 6.25, 12.5, 25, and 50. The mechanism of resistance to the stress by factor was examined with the decrease in the regeneration and viability of leaves and roots; both measured by unit or percentage for 45 to 75 days, since the plants in vitro did not produce ramets. In NR1 experiments, all plants died in 100% CN and leaves registered greater resistance with 24N:P, and 25% CN (p 0.05). In RN2 experiments, leaves and roots resisted at 72N:P, within the percent ranging from 6.25 to 25 CN (p

Background. Thirty species were previously recorded for unstructured habitats (unvegetated soft substrates: USS) in Pantanos de Centla. However, a lack of information on the tropical ichthyofauna of the structured habitats such as marginal vegetation (MV), submerged macrophytes (SM) and coarse woody debris (CWD) emphasizes the importance of the aim of this paper that is the updating the records of the species distributed in these habitats, as they have been frequently reported as high biodiversity sites that are currently threatened by anthropogenic activities. Materials and methods. Sampling was carried out in 30 shallow sites, each with unstructured habitats and the three structured habitats, in Pantanos de Centla, a Ramsar wetland, over a period of three years. Fish were collected with a dip net, a drop net and a Renfro beam net. Results. A total of 6506 fish of 37 genera and 44 species were collected. Eleven species are new records for Pantanos de Centla, and the scientific name of 11 species was updated. The Poeciliidae and Cichlidae families are dominant with 10 and 13 species, respectively. Nine species of the genus Cichlasoma sensu lato were placed in six genera. Three species are new records for the Usumacinta Province. Ctenogobius claytoni, Gobionellus oceanicus, and Rhamdia quelen proved to be synonyms. Of all species, 84% were collected from USS, however, the number of species distributed in USS, MV, and SM was similar (CCj 0.4736-0.5813). Conclusion. Most of the species that were added to the previously recorded species list of Pantanos de Centla, inhabit structured habitats. This confirms the importance of including these habitats in surveys aimed at generating checklists, and of analysing the distribution of fish species in shallow tropical ecosystems.

[The blue crab, Callinectes sapidus is an abundant predator that is widely distributed throughout the estuarine ecosystems of the eastern United States and the Gulf of Mexico. The mortality rate of four epibenthic prey species was analysed over a 24 hour trial period in order to test the effect of prey mobility, prey density, and quantitative habitat complexity on the predation rate of adult blue crabs. Habitat complexity conditions included, from low to high complexity, unvegetated substrates, sparse seagrass (300 stems/m 2 ), and dense seagrass (1200 stems/m 2 ). Prey included low mobility species (hermit crabs), medium mobility species on the substrate (juvenile blue crabs), medium mobility species in the water column (pink shrimp), and high mobility species in the water column (assemblage of juvenile fish). Preys were analysed at low, medium-low, medium-high, and high densities. C . sapidus consumed more prey in the dense seagrass habitat than in the sparse seagrass habitat (F = 7.45; p = 0.007). Predation of pink shrimp was significantly greater than that of the other three prey species (F = 60.33; p 0.0001), and was followed by fish. Also, mortality by blue crab predation was greatest at all four densities for the pink shrimp and at the medium-low density for the fish (F = 69.4; p 0.0001), whereas the other density*prey combinations were similar. The predator C . sapidus used an ambush strategy for mobile prey in the more complex habitats, whereas it pursued the less mobile prey in the less complex habitats, as the hypothesis proposed. Mortality by predation by the adult blue crab was regulated more by the habitat complexity-prey type relationship than by the availability of prey in the various habitats. La jaiba azul Callinectes sapidus es un depredador abundante y ampliamente distribuido en los ecosistemas estuarinos en la costa este de Estados Unidos y Golfo de Mexico. La tasa de mortalidad de cuatro especies de presas epibenticas fue analizada durante un periodo de experimentacion de 24 horas para evaluar el efecto de la movilidad de presa, densidad de presa y complejidad cuantitativa del habitat sobre la tasa de depredacion de la jaiba azul adulta. Las condiciones de complejidad del habitat incluyeron desde reducida hasta elevada complejidad como sustratos sin vegetacion, baja densidad (300 tallos/m 2 ) y alta densidad (1200 tallos/m 2 ) de pastos marinos. Los tipos de presas fueron de baja movilidad (cangrejo ermitano), mediana movilidad sobre el sustrato (jaiba juvenil), mediana movilidad en el agua (camaron) y alta movilidad en la columna de agua (peces juveniles), las cuales fueron utilizadas en densidades baja, media-baja, media-alta y alta. C. sapidus consumio mas presas en densidad elevada de pastos marinos que en densidad minima de pastos marinos (F = 7,45; p = 0,007). La depredacion de camarones rosados fue significativamente mayor que para los otros tres tipos de presas (F = 60,33; p 0,0001), y fue seguida por los peces. Tambien, la mortalidad por depredacion de la jaiba azul fue mayor en todas las densidades del camaron rosado y en la densidad media-baja de peces (F = 69,4; p 0,0001), ya que en las restantes combinaciones densidad*presa resultaron similares. El depredador C . sapidus utilizo una estrategia de acechador sobre presas de alta movilidad en complejidad estructural elevada, mientras que fue un perseguidor con presas de menor movilidad en complejidad estructural baja, como lo propone la hipotesis. La mortalidad por depredacion por las jaibas azules adultas fue regulada mas por la relacion tipo de presa-complejidad del habitat que por la probabilidad de encontrar a la presa en varios habitat. , The blue crab, Callinectes sapidus is an abundant predator that is widely distributed throughout the estuarine ecosystems of the eastern United States and the Gulf of Mexico. The mortality rate of four epibenthic prey species was analysed over a 24 hour trial period in order to test the effect of prey mobility, prey density, and quantitative habitat complexity on the predation rate of adult blue crabs. Habitat complexity conditions included, from low to high complexity, unvegetated substrates, sparse seagrass (300 stems/m 2 ), and dense seagrass (1200 stems/m 2 ). Prey included low mobility species (hermit crabs), medium mobility species on the substrate (juvenile blue crabs), medium mobility species in the water column (pink shrimp), and high mobility species in the water column (assemblage of juvenile fish). Preys were analysed at low, medium-low, medium-high, and high densities. C . sapidus consumed more prey in the dense seagrass habitat than in the sparse seagrass habitat (F = 7.45; p = 0.007). Predation of pink shrimp was significantly greater than that of the other three prey species (F = 60.33; p 0.0001), and was followed by fish. Also, mortality by blue crab predation was greatest at all four densities for the pink shrimp and at the medium-low density for the fish (F = 69.4; p 0.0001), whereas the other density*prey combinations were similar. The predator C . sapidus used an ambush strategy for mobile prey in the more complex habitats, whereas it pursued the less mobile prey in the less complex habitats, as the hypothesis proposed. Mortality by predation by the adult blue crab was regulated more by the habitat complexity-prey type relationship than by the availability of prey in the various habitats. La jaiba azul Callinectes sapidus es un depredador abundante y ampliamente distribuido en los ecosistemas estuarinos en la costa este de Estados Unidos y Golfo de Mexico. La tasa de mortalidad de cuatro especies de presas epibenticas fue analizada durante un periodo de experimentacion de 24 horas para evaluar el efecto de la movilidad de presa, densidad de presa y complejidad cuantitativa del habitat sobre la tasa de depredacion de la jaiba azul adulta. Las condiciones de complejidad del habitat incluyeron desde reducida hasta elevada complejidad como sustratos sin vegetacion, baja densidad (300 tallos/m 2 ) y alta densidad (1200 tallos/m 2 ) de pastos marinos. Los tipos de presas fueron de baja movilidad (cangrejo ermitano), mediana movilidad sobre el sustrato (jaiba juvenil), mediana movilidad en el agua (camaron) y alta movilidad en la columna de agua (peces juveniles), las cuales fueron utilizadas en densidades baja, media-baja, media-alta y alta. C. sapidus consumio mas presas en densidad elevada de pastos marinos que en densidad minima de pastos marinos (F = 7,45; p = 0,007). La depredacion de camarones rosados fue significativamente mayor que para los otros tres tipos de presas (F = 60,33; p 0,0001), y fue seguida por los peces. Tambien, la mortalidad por depredacion de la jaiba azul fue mayor en todas las densidades del camaron rosado y en la densidad media-baja de peces (F = 69,4; p 0,0001), ya que en las restantes combinaciones densidad*presa resultaron similares. El depredador C . sapidus utilizo una estrategia de acechador sobre presas de alta movilidad en complejidad estructural elevada, mientras que fue un perseguidor con presas de menor movilidad en complejidad estructural baja, como lo propone la hipotesis. La mortalidad por depredacion por las jaibas azules adultas fue regulada mas por la relacion tipo de presa-complejidad del habitat que por la probabilidad de encontrar a la presa en varios habitat. ]

A total of 24 Uhlorchestia uhleri (Shoemaker, 1930) females were identified from 3,828 amphipods found in 1,402 samples from 31 sampling sites. At each locality, amphipods were collected from uncovered soft substrates and marginal vegetation, whereas sampling in coarse woody debris depended on the local availability of that habitat. Submerged aquatic vegetation consisted of Vallisneria americana (Michx.) or Cabomba palaeformis (Fassett). The amphipods were identified following Bousfield & Heard (1986) and the specimens are deposited in the Colecci?n Nacional de Crust?ceos, UNAM. Ilustrations were made with a microscope and drawing attachment. The 24 U. uhleri specimens were collected in salinities lower than 0.5%o, 20 females from the roots of the water hyacinth, Eichhornia crassipes (Mart.) in the R?o Playa, an artificial canal connected to the Rio El Moral 5.8 km inland (18?20/N 93?18'W) in the Coatzacoalcos basin, and the other four specimens from Rhizophora mangle (L.) roots in the lagoons of San Pedrito (18?23'N 92?34.5'W), El Cometa (18?27.5'N 92?26.25'W), El Coco (18?28.74'N 92?41.48/W), and

Hermit crabs were collected over 13 years from different habitats in the coastal lagoons of Terminos, Alvarado, Tamiahua, and Madre in the southwestern Gulf of Mexico. The distribution, habitat, relative abundance, shield-length data, and zoogeographical affinities of each of the ten species are presented. A zoogeographical analysis assigned the species to four distribution patterns: Eurytopic (Clibanarius vittatus, Petrochirus diogenes, Paguristes tortugae, Pagurus criniticornis); Endemic to the Gulf of Mexico (Paguristes hernancortezi); Warm-Temperate Caribbean (P. hummi, Pagurus maclaughlinae); and Warm-Temperate (P. annulipes, P. longicarpus, P. pollicaris). Five species extend their previously recorded distribution southward, and eight species are now recorded further south within the Gulf of Mexico.

Alberto J. Sanchez1, Rosa Florido1, Miguel Angel Salcedo1, Violeta Ruiz-Carrera1, Hugo Montalvo-Urgel2 and Andrea Raz-Guzman3 1Diagnostico y Manejo de Humedales Tropicales, CICART, Division Academica de Ciencias Biologicas, Universidad Juarez Autonoma de Tabasco, Tabasco 2Posgrado en Ciencias Ambientales, Division Academica de Ciencias Biologicas, UJAT 3Instituto de Ciencias del Mar y Limnologia, UNAM Mexico

ResumenLos registros de 3,967 ejemplares de Pterygoplichthys spp. en 6 asociaciones de macrófitas acuáticas en 6 zonas de humedales confirman su dispersión en la cuenca baja de los ríos Grijalva-Usumacinta. Los loricáridos en vegetación enraizada sumergida merecen mayor atención, pues representan un riesgo más para estas asociaciones de macrófitas acuáticas que albergan elevada biodiversidad.AbstractThe records of 3,967 specimens of Pterygoplichthys spp. in 6 associations of aquatic macrophytes in 6 areas of wetlands confirm its dispersion in the lower basin of the Grijalva-Usumacinta rivers. The loricariids in submerged rooted vegetation need attention, since they represent another risk for these associations of aquatic macrophytes, which shelter high biodiversity.

The dynamics and structure of aquatic communities are affected by the habitat complexity as diversity and abundance increase with the availability of structured habitats such as coarse woody debris that provides sites used for refuge, feeding and reproduction. Manual sampling of the fauna associated with this habitat was carried out twice during the season of maximum floods and once during minimum flooding, in 18 lagoons of Pantanos de Centla with coarse woody debris. The 1 228 crustaceans collected belong to 4 orders, 11 families, 11 genera and 13 species, among which malacostracans dominated with 12 species. The 13 species of crustaceans reported here represented 17% of the total carcinofauna recorded in the freshwater ecosystems of Tabasco. The amphipod Hyalella azteca was the numerically dominant species. The distribution of Balanus improvisus, Uhlorchestia ulheri, Platychirograpsus spectabilis, Armases cinereum and Goniopsis cruentata was restricted mainly to the area of marine influence. Moreover, B. improvisus and Sphaeroma terebrans were the only 2 sessile and wood-boring species. Coarse woody debris is also an alternative habitat for the other 11 species.