Variability of coastal suprabenthic assemblages from sandy beaches of the Caribbean coast of Venezuela.

The suprabenthos or hyperbenthos is the macrofaunal assemblage of small-sized organisms that interact for some time in the benthic boundary layer. Information about the taxonomic composition and role of suprabenthic species, especially in littoral zones, is scarce and scattered. This work attempts to contribute alleviate this problem. We analyze the temporal and spatial variations of suprabenthic assemblages in the swash-zone from four beaches of the littoral coast of Venezuela. For each beach, two sites were chosen, and special attention was given to water and sediment characteristics. 12 environmental variables were measured: Dissolved oxygen, oxygen saturation percentage, pH, salinity, surface temperature, total, organic and inorganic suspended solids, total organic carbon, organic matter in sediment, grain size of sediment, and amount of dragged material of sample. All faunal samples were taken on a monthly basis during 2011; these were extracted using a manual suprabenthic sledge towed parallel to the shoreline. Samples were sorted and identified to their lowest possible taxonomic level. A total of 24 141 specimens (mean abundance: 26.16 +/- 55.35 ind./m2) belonging to 21 taxonomic groups were identified. Analysis suggests that seasonality does not explain observed changes either in fauna or environmental variables. It was found that suprabenthic assemblages, total suprabenthos density, richness and environmental variables changed in a dissimilar fashion between months and beaches. The most frequent groups were amphipods and decapods; and at the species/categories level post-larval shrimp (Penaeidae), Grapsidae crab megalopae and Arenaeus cribarius megalopae were common. Dissimilarity between months in each beach was primarily explained by the abundance of amphipods, ctenophores, decapods and mysids. For particular months and selected beaches very high abundances of ctenophores were found. This group dominated the sample even though it is not usually a representative group in suprabenthos. Samples showed low correlations between suprabenthos and environmental variables. A somewhat stronger correlation could be established between water characteristics and dragged material abundance. The studied suprabenthos assemblage was found to have high taxa richness and very dynamic behaviour at spatial and temporal scale. Further analysis suggested that there is no evident pattern of distribution and that causality can not be directly attributed to temporal variation only. Possibly there is an influence of a synergy of environmentals or biological factors, rather than a single variable. The species Americamysis bahia and Americamysis taironana are reported for the first time in Venezuela. This study represents the first ecological research of the suprabenthos in the Caribbean region.

Variability of coastal suprabenthic assemblages from sandy beaches of the Caribbean coast of Venezuela / Variabilidad de agregaciones suprabentónicas costeras de playas arenosas de la costa Caribe de Venezuela

The suprabenthos or hyperbenthos is the macrofaunal assemblage of small-sized organisms that interact for some time in the benthic boundary layer. Information about the taxonomic composition and role of suprabenthic species, especially in littoral zones, is scarce and scattered. This work attempts to contribute alleviate this problem. We analyze the temporal and spatial variations of suprabenthic assemblages in the swash-zone from four beaches of the littoral coast of Venezuela. For each beach, two sites were chosen, and special attention was given to water and sediment characteristics. 12 environmental variables were measured: Dissolved oxygen, oxygen saturation percentage, pH, salinity, surface temperature, total, organic and inorganic suspended solids, total organic carbon, organic matter in sediment, grain size of sediment, and amount of dragged material of sample. All faunal samples were taken on a monthly basis during 2011; these were extracted using a manual suprabenthic sledge towed parallel to the shoreline. Samples were sorted and identified to their lowest possible taxonomic level. A total of 24 141 specimens (mean abundance: 26.16±55.35ind./m²) belonging to 21 taxonomic groups were identified. Analysis suggests that seasonality does not explain observed changes either in fauna or environmental variables. It was found that suprabenthic assemblages, total suprabenthos density, richness and environmental variables changed in a dissimilar fashion between months and beaches. The most frequent groups were amphipods and decapods; and at the species/categories level post-larval shrimp (Penaeidae), Grapsidae crab megalopae and Arenaeus cribarius megalopae were common. Dissimilarity between months in each beach was primarily explained by the abundance of amphipods, ctenophores, decapods and mysids. For particular months and selected beaches very high abundances of ctenophores were found. This group dominated the sample even though it is not usually a representative group in suprabenthos. Samples showed low correlations between suprabenthos and environmental variables. A somewhat stronger correlation could be established between water characteristics and dragged material abundance. The studied suprabenthos assemblage was found to have high taxa richness and very dynamic behaviour at spatial and temporal scale. Further analysis suggested that there is no evident pattern of distribution and that causality can not be directly attributed to temporal variation only. Possibly there is an influence of a synergy of environmentals or biological factors, rather than a single variable. The species Americamysis bahia and Americamysis taironana are reported for the first time in Venezuela. This study represents the first ecological research of the suprabenthos in the Caribbean region.

El suprabentos o hiperbentos es la agregación de organismos de pequeño tamaño que interactúan por cierto tiempo en la capa de límite bentónico. La información de la composición taxonómica y el papel de las especies suprabentónicas, especialmente en la zona litoral, es escasa. Este trabajo trata de contribuir a solventar este problema. Se analizó la variación espacial y temporal de la agregación suprabentónica en la zona de rompiente de cuatro playas en la costa litoral de Venezuela. Se dio especial atención al sedimento y características del agua. Todas las muestras fueron tomadas mensualmente durante el 2011. Las muestras fueron extraídas utilizando un trineo suprabentónico manual paralelo a la línea de costa. En cada playa se escogieron dos sitios. Las muestras fueron separadas e identificadas hasta el nivel taxonómico más bajo posible. Se midieron doce variables ambientales: oxígeno disuelto, porcentaje de saturación de oxígeno, pH, salinidad, temperatura superficial, sólidos suspendidos totales, inorgánicos y orgánicos, carbono orgánico total, materia orgánica en sedimento, tamaño del grano de sedimento y cantidad de material arrastrado en cada muestra. Se identificaron un total de 24 141 individuos (densidad promedio: 26.16±55.35ind./m2), pertenecientes a 21 grupos taxonómicos. Los análisis sugieren que la estacionalidad no explica los cambios observados en la fauna ni en las variables ambientales. La agregación del suprabentos, la densidad total, riqueza y variables ambientales cambiaron de manera diferente entre meses y playas. Los grupos más frecuentes fueron anfípodos y decápodos. A nivel de especies/categorías fueron las post-larvas de camarón (Penaeidae), las megalopas de cangrejos Grapsidae y de Arenaeus cribarius (Lamarck, 1818). La disimilitud entre meses en cada playa se debe principalmente a la abundancia de anfípodos, ctenóforos, decápodos y misidáceos. En meses particulares y algunas playas, se encontraron altas abundancias de ctenóforos. Este grupo dominó esas muestras, aún cuando no son frecuentemente un grupo representativo del suprabentos. Se encontraron bajas correlaciones entre el suprabentos y las variables ambientales. Una relación un poco más fuerte fue establecida con las características del agua y la abundancia de material arrastrado. La agregación de suprabentos estudiada tuvo una alta riqueza taxonómica y fue muy dinámica tanto espacial como temporalmente. Los análisis sugieren que no hay un patrón evidente de distribución y el azar no puede ser atribuido sólo a la variación temporal. Posiblemente hay influencia de una sinergia de factores ambientales o biológicos, más que de una variable en particular. Las especies Americamysis bahia (Molenock, 1969) y Americamysis taironana (Brattegard, 1973) se reportan por primera vez para Venezuela. Este es el primer estudio ecológico del suprabentos en el Mar Caribe.

Biodiversidad de crustáceos peracáridos en el delta del Río Orinoco, Venezuela / Biodiversity of peracarid crustaceans in the Orinoco River Delta, Venezuela

The composition, abundance, diversity and density of benthonic peracarid crustaceans were studied in the Orinoco river delta, Venezuela. Samples were collected at 18 sites distributed in five areas: one at the high delta, two at the medium sector and two at the low delta. Two field seasons were included: high waters (18-28 November 2002) and low waters (8-19 May 2003). Three samples were dredged at each sampling site, identifying more than 510 specimens belonging to eight families and 11 species: Amphipoda (three families, six species), Isopoda (one family, one species), Tanaidacea (two families, three species), Cumacea (one family) and Mysida (one family, one species). Two species (Discapseudes surinamensis and Halmyrapseudes spaansi) and an unidentified species of Kalliapseudes are new records for Venezuela. Their density and distribution suggest that a salinity gradient influenced longitudinal distribution: greater densities and species richness were in the lower delta, near the mouth of the Mariusa and Winikina rivers.

Para evaluar la composición, abundancia, diversidad y densidad de crustáceos peracáridos en los sedimentos de la región del delta del río Orinoco (Venezuela), establecimos cinco áreas de muestreo: una en el alto delta, dos en el sector medio y dos en el bajo delta (18 estaciones). Hicimos dos muestreos de campo: época de “aguas altas” o lluvia (18-28 noviembre/2002) y “aguas bajas” o sequía (8-19 de mayo, 2003). Tomamos tres muestras de bentos mediante dragas, identificando un total de 515 individuos, pertenecientes a 8 familias y 11 especies en total: Amphipoda (tres familias, seis especies), Isopoda (una familia, una especie), Tanaidacea (dos familias, tres especies), Cumacea (una familia) y Mysida (una familia, una especie), de las cuales dos fueron nuevas citas para el país: Discapseudes surinamensis y Halmyrapseudes spaansi, así como una especie no identificada de Kalliapseudes. La densidad y distribución de estos organismos sugiere la existencia de gradientes de influencia marina, con las mayores densidades y riqueza de especies en áreas cercanas a las desembocaduras de los caños Mariusa y Winikina.

Lista y referencias de los crustáceos anfípodos (Amphipoda: Gammaridea) del Atlántico occidental tropical

Checklist and references of the Amphipod Crustaceans (Gammaridea) from tropical western Atlantic. The published records of Amphipoda Gammaridea of the tropical western Atlantic region were reviewed and compiled in a checklist. A total of 478 species is recorded (52 families, 199 genera). This adds 20 families and 253 species to the last published list. The families are Ampeliscidae, Amphilochidae, Amphitoidae, Anamixidae, Aoridae, Argissidae, Aristiidae, Bateidae, Biancolinidae, Bogidiellidae, Cheluridae, Colomastigidae, Corophiidae, Cyphocarididae, Cyproideidae, Dexaminidae, Endevouridae, Epimeriidae, Eusiridae, Gammaridae, Hadziidae, Haustoriidae, Hyalellidae, Hyalidae, Hyperiopsidae, Iphimediidae, Isaeidae, Ischyroceridae, Leucothoidae, Liljeborgiidae, Lysianassidae, Megaluropidae, Melitidae, Melphidippidae, Ochlesidae, Oedicerotidae, Pardaliscidae, Phliantidae, Phoxocephalidae, Platyischnopidae, Pleustidae, Podoceridae, Pontoporeiidae, Scopelocheiridae, Sebidae, Stegocephalidae, Stenothoidae, Synopiidae, Talitridae, Uristidae, and Vitjazianidae. Rev. Biol. Trop. 55 (2): 479-498 (Foliación únicamente para la versión digital: 479-528). Epub 2007 June, 29.

Se presenta una lista actualizada de los anfípodos gamarideos del Atlántico occidental tropical, la cual contiene 51 familias y 475 especies. En comparación con trabajos anteriores, el número de familias y especies de esta región se incrementó en 20 y 250, respectivamente. Las familias presentes en la lista son las siguientes: Ampeliscidae, Amphilochidae, Amphitoidae, Anamixidae, Aoridae, Argissidae, Aristiidae, Bateidae, Biancolinidae, Bogidiellidae, Cheluridae, Colomastigidae, Corophiidae, Cyphocarididae, Cyproideidae, Dexaminidae, Endevouridae, Epimeriidae, Eusiridae, Gammaridae, Hadziidae, Haustoriidae, Hyalellidae, Hyalidae, Hyperiopsidae, Iphimediidae, Isaeidae, Ischyroceridae, Leucothoidae, Liljeborgiidae, Lysianassidae, Megaluropidae, Melitidae, Melphidippidae, Ochlesidae, Oedicerotidae, Pardaliscidae, Phliantidae, Phoxocephalidae, Platyischnopidae, Pleustidae, Podoceridae, Pontoporeiidae, Scopelocheiridae, Sebidae, Stegocephalidae, Stenothoidae, Synopiidae, Talitridae, Uristidae y Vitjazianidae.

[Checklist and references of the Amphipod Crustaceans (Gammaridea) from tropical western Atlantic]. / Lista y referencias de los crustáceos anfípodos (Amphipoda: Gammaridea) del Atlántico occidental tropical.

The published records of Amphipoda Gammaridea of the tropical western Atlantic region were reviewed and compiled in a checklist. A total of 478 species is recorded (52 families, 199 genera). This adds 20 families and 253 species to the last published list. The families are Ampeliscidae, Amphilochidae, Amphitoidae, Anamixidae, Aoridae, Argissidae, Aristiidae, Bateidae, Biancolinidae, Bogidiellidae, Cheluridae, Colomastigidae, Corophiidae, Cyphocarididae, Cyproideidae, Dexaminidae, Endevouridae, Epimeriidae, Eusiridae, Gammaridae, Hadziidae, Haustoriidae, Hyalellidae, Hyalidae, Hyperiopsidae, Iphimediidae, Isaeidae, Ischyroceridae, Leucothoidae, Liljeborgiidae, Lysianassidae, Megaluropidae, Melitidae, Melphidippidae, Ochlesidae, Oedicerotidae, Pardaliscidae, Phliantidae, Phoxocephalidae, Platyischnopidae, Pleustidae, Podoceridae, Pontoporeiidae, Scopelocheiridae, Sebidae, Stegocephalidae, Stenothoidae, Synopiidae, Talitridae, Uristidae, and Vitjazianidae.

Morfometría de Sanguinolaria cruenta (Bivalvia: Psammobidae) en playa Tucacas, Falcón, Venezuela / Morphometry of Sanguinolaria cruenta (Bivalvia: Psammobidae) in Tucacas Beach, Falcón, Venezuela)

Three hundred and twelve shells of Sanguinolaria cruenta were collected in May 1999 in a sandy beach in Tucacas, Falcón, Venezuela. For each shell, antero-posterior length (Lap), overall height (Al), wide (An), weight (Pe), valves area (Arv), anterior length (La) and dorsal height (Ad) were measured. The descriptive statistic of the studied individuals, allows to appreciate that the variables that are good as parameters for the taxonomic description of S. cruenta are: Lap, Al, An, La y Ad, given their little variability. The maximum class frequencies is 41-70 mm for Lap (91 of the population). Analysis of data determined relationships of Lap to An, Lap to La were isometric (Lap = 0.98078 An + 1.50456 and Lap = 0.98052 La + 5.25840, respectively), whereas the other relationships indicate allometric growth.