Ivan Hernandez | Universidad de Oriente (original) (raw)
Papers by Ivan Hernandez
Zootaxa, 2010
A reassessment of the adult and larval morphology as well as comparison with published molecular ... more A reassessment of the adult and larval morphology as well as comparison with published molecular information confirms the monophyly of the genus Calyptraeotheres , and its relationship with Dissodactylus Smith, 1870, Clypeasterophilus Campos & Griffith, 1990 and Tumidotheres Campos, 1990. Calyptraeotheres pepeluisi new species, is described from Michoacán, Mexico on the basis of a female specimen. The new species is distinguished from the other nominal species of the genus by having a subarcuate carapace with longer setae on its front and anterolateral margin, the eyes are dorsally visible, and a third maxilliped with a 2-segmented palp and a conical propodus.
Zootaxa, 2007
Parapinnixa bolagnosi new species, is described from Cubagua Island and Los Frailes Archipelago i... more Parapinnixa bolagnosi new species, is described from Cubagua Island and Los Frailes Archipelago in the Caribbean Sea off Venezuela based on female specimens. The new species is distinguished from the other nominal species of the genus by having a ...
Zootaxa
All sipunculan species currently known to occur on the Caribbean coast of Venezuela and Curaçao a... more All sipunculan species currently known to occur on the Caribbean coast of Venezuela and Curaçao are reviewed. Included are species previously reported in the primary literature and those collected by Cutler (EBC) in 1987/1988 and Hernández-Ávila (IHA) in 2003/2004. Nineteen species of sipunculans belonging to eleven genera are known from this region. Most specious is the genus Aspidosiphon with seven species and the genus Phascolosoma with three species.
Proceedings of the Biological …, Jan 1, 2006
Calyptraeotheres hernandezi is described from off Cubagua Island, Caribbean Sea, Venezuela. The n... more Calyptraeotheres hernandezi is described from off Cubagua Island, Caribbean Sea, Venezuela. The new species resembles C. granti (Glassell, 1933) from the eastern Pacific, with both taxa possessing a third maxilliped with an endopod palp of only two segments, ie, ...
Bol. Inst. …, 2008
RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del micr... more RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del microfitoplancton de la Bahía de Charagato, relacionados con los cambios hidrográficos. Para ello fueron realizados muestreos mensuales determinando in situ la ...
![Research paper thumbnail of [Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagua Island, Venezuela]](https://attachments.academia-assets.com/44302840/thumbnails/1.jpg)
](Revista de biología tropical, 2013
Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, sub... more Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (C...
The crustacean decapod fauna of Cubagua Island in the Caribbean Sea, Venezuela, an island much af... more The crustacean decapod fauna of Cubagua Island in the Caribbean Sea, Venezuela, an island much affected by coastal upweling, was surveyed. A total of 178 species from 41 families were recorded, of which 56 species were new records for the island; eigth genera and six species were new records for Venezuela. Most species had previously been recorded from the the
Revista de biología marina y oceanografía, 2008
Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the... more Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the first record of N. antilocapra for Venezuela, and for the south Caribbean area. Nibilia antilocapra can be separated from other species of the family Epialtidae by the following features: wide postorbital tooth forming a cup, supraocular eave and postocular cup well separated, with a small tooth between them. Carapace pyriform, longer than wide, with several spines of different size on the surface. Chelipeds stouter than the walking leg, the formers diminish gradually in size. Four species of the subfamily Pisinae have been recorded for Venezuela marine waters.
Fertilized eggs from an spontaneously spawn of thirty sexually mature sea urchins (Arbacia punctu... more Fertilized eggs from an spontaneously spawn of thirty sexually mature sea
urchins (Arbacia punctulata) were incubated to complete embryonic development. The echinopluteus larvae
(3 ind/ml) were distributed into 50 plastic containers (25 containers at 30 psu and 25 containers at 40 psu) and
fed on Tetraselmis chuii, Nannochloropsis oculata, Isochrysis galbana, Chaetoceros gracilis and C. calcitrans
under a natural photoperiod. The water of the containers was partially renewed (75%) everyday. Larval anatomic
development aspects, daily survival and growth were determined. The growth was determined through postoral
arms and body length measurement, and body diameter of twelve larvae during metamorphosis. During the
planktonic larval phase, only the I. galbana diet produced similar results for both salinities. The relative growth
of larvae was isometric (I) for larvae fed on I. galbana at two salinities and positive allometric for those fed on
C. gracilis and C. calcitrans at both salinities. In this study A. punctulata started metamorphosis at day 14 and
was completed 30 days after fecundation. Significant differences were detected in post-settlement body growth
between the two salinities (F=23.58, p<0.05): growth was better for larvae at 30 psu (final body diameter was
3.14 ± 0.44 mm). The final rate of planktonic larvae was highest with I. galbana (58.33%). For juveniles the rate
was 6.48% for those fed on C. gracilis (40 psu in both larvae and juveniles). We recommend the use of this diet
and 40 psu for survival or 30 psu for growth
se incluyen los valores promedio de abundancia (ind/m 3 ) y la contribución acumulada de cada gru... more se incluyen los valores promedio de abundancia (ind/m 3 ) y la contribución acumulada de cada grupo (% cA).
Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagu... more Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagua Island, Venezuela. Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (Calyptraeidae) and Ophiotrix angulata (Ophiothrichidae) were the most common species found in these assemblages. The medium and high-density bivalve beds exhibited greater species number, abundance, Shannon diversity, evenness, taxonomic diversity, and taxonomic distinctness of associated fauna, than low-density bivalve beds. Moreover, multivariate analysis detected different assemblages of associated fauna between beds with different densities. Additionally, similarities were found in the communities of macrofauna in both beds of P. imbricata and Arca zebra. Our results suggest that bivalve aggregations at Cubagua Island provide additional habitat for macrofauna living in other shallow habitats such as Thalassia beds, corals and rocky environments. Bed density, associated with topographic complexity, represents an important factor for the composition and complexity of the associated fauna. Rev. Biol. Trop. 61 (2): 669-682. Epub 2013 June 01.
Beds of the Atlantic pearl oyster (Pinctada imbricata) and the turkey wing (Arca zebra) of contra... more Beds of the Atlantic pearl oyster (Pinctada imbricata) and the turkey wing (Arca zebra) of contrasting population densities were evaluated to determine the occurrence of associated decapod crustaceans. In these beds at Cubagua Island, Venezuela, we recorded 40 decapod species belonging to 18 families. Mithraculus forceps (Majidae), Pilumnus caribaeus (Pilumnidae), Cuapetes americanus (Palaemonidae) and Petrolisthes galathinus (Porcellanidae) were the most common species found in these assemblages. The medium-and high-density bivalve beds exhibited more species and a greater abundance of associated decapods than the low-density bivalve beds, and more taxonomic distinctness. Multivariate analysis detected different groups of decapods in the low-density beds and the medium-to high-density beds. Additionally, similarities were found in the communities of crustaceans in the beds of Atlantic pearl oysters and turkey wing, demonstrating that bed density is important for the composition of associated fauna. RESUMEN: Composición de ensambles de crustáceos decápodos en bancos de Pinctada imbricata y arca zebra (Mollusca: Bivalvia) en la Isla de Cubagua, Venezuela: Efecto de la densidad del banco. -Bancos de la ostra perla del Atlántico (P. imbricata) y de la pepitona (A. zebra) de densidades poblacionales contrastantes fueron evaluados para determinar la ocurrencia de crustáceos decápodos asociados. En estos bancos en la isla de Cubagua, Venezuela, fueron colectadas 40 especies de decápodos, pertenecientes a 18 familias. Mithraculus forceps (Majidae), Pilumnus caribaeus (Pilumnidae), Cuapetes americanus (Palaemonidae) y Petrolisthes galathinus (Porcellanidae) fueron las especies más comunes en estos ensambles. Los bancos de densidad media y alta mostraron mayor riqueza de especies y abundancia que los de baja densidad de bivalvos, así como mayor distinción taxonómica. Análisis multivariados detectaron diferentes grupos de decápodos en los bancos de baja densidad en relación a los de densidad media y alta. Adicionalmente, la fauna encontrada en bancos de ostra perla y pepitona no mostró diferencias, demostrando que la densidad es importante para la composición de la fauna asociada.
Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the... more Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the first record of N. antilocapra for Venezuela, and for the south Caribbean area. Nibilia antilocapra can be separated from other species of the family Epialtidae by the following features: wide postorbital tooth forming a cup, supraocular eave and postocular cup well separated, with a small tooth between them. Carapace pyriform, longer than wide, with several spines of different size on the surface. Chelipeds stouter than the walking leg, the formers diminish gradually in size. Four species of the subfamily Pisinae have been recorded for Venezuela marine waters.
RESUMEN: Durante un estudio bionómico de la isla de Cubagua fue colectado un espécimen de Tyche e... more RESUMEN: Durante un estudio bionómico de la isla de Cubagua fue colectado un espécimen de Tyche emarginata, lo cual constituye el primer registro para aguas venezolanas. El espécimen macho 22 mm longitud del caparazón) fue capturado entre rocas a 3,5 m de profundidad. Entre los caracteres diagnósticos se encuentran: Caparazón oblongo-oval, borde fronto-orbital poco menos el ancho del caparazón, con cuatro cuernos, dos submesiales paralelos y dos laterales divergentes. Región gástrica elevada, región cardíaca deprimida, con tres tubérculos cada una. Bordes laterales rectos en la región hepática, redondeados en la branquial. Región hepática cóncava. Tercer maxilípedo con una protuberancia basal en el exópodo que se proyecta sobre el isquio, margen interno del isquio fuertemente dentado. Longitud del quelípedo más del doble de la sección post-orbital del caparazón. El presente hallazgo es el primer registro del género en Venezuela, elevándose a 48 las especies de majoideos registrados en aguas venezolanas, cinco pertenecientes a la familia Tychidae.
RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del micr... more RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del microfitoplancton de la bahía de Charagato, relacionados con los cambios hidrográficos. Para ello fueron realizados muestreos mensuales determinando in situ la temperatura y salinidad y colectando muestras a 0 y 5 m de profundidad a 100 m de la costa y a 0, 5, 10 y 20 m a 1 km, para determinar concentraciones de amonio, nitrito, nitrato, fosfato, clorofila a, feopigmentos y para los análisis cualitativos y cuantitativos del fitoplancton por el método Utermöhl. Además, fue determinada la dirección y la velocidad del viento. No fueron detectadas diferencias significativas tanto en la hidrografía y del fitoplancton entre las estaciones ni entre las profundidades estudiadas. Sin embargo, fueron observadas variaciones estacionales con menores temperaturas y mayores concentraciones de nutrientes en julio/2003 y durante enero-marzo/2004, que estuvieron asociadas al proceso de surgencia costera de la región. Se identificaron 320 especies de microfitoplancton, principalmente de diatomeas y dinoflagelados. Entre las más frecuentes y abundantes, se encontró: Nitszchia longissima, Pseudonitszchia delicatissima, Cylindroteca closterium, Thalassionema nitszchioides y Emiliana huxleyi. Las variaciones temporales de la composición y abundancia fitoplanctónica estuvieron asociadas a la ocurrencia estacional del proceso del surgencia, pero con un aparente desfase entre los procesos meteorológicos, hidrográficos y biológicos.
RESUMEN: En la costa este de Margarita durante 39 meses (2002)(2003)(2004)(2005) quincenalmente s... more RESUMEN: En la costa este de Margarita durante 39 meses (2002)(2003)(2004)(2005) quincenalmente se estudió la abundancia y composición del zooplancton nocturno en dos estaciones (Guacuco y Porlamar) localizadas a 5 millas de la costa. Se utilizo una red de plancton (diámetro de 1,7 m; longitud de 3,5 m; abertura de malla de 400 micras) arrastrada durante 20 minutos a profundidad de 10-15 m. Se encontraron representantes de 21 grupos y se contabilizaron 6.688.352 individuos. En Guacuco la densidad del zooplancton varió entre 6,28 y 385,91 ind m -3 (promedio 61,53), la biomasa seca entre 0,43 y 14,34 mg m -3 -(promedio 2,10) y el volumen sedimentado entre 0,02 y 0,70 ml m 3 -(promedio de 0,13). En Porlamar la densidad varió entre 7,55 y 537,78 ind m 3 -(promedio 49,11), la biomasa seca entre 0,26 y 4,63 mg m 3 -con (promedio 1,83) y el volumen sedimentado entre 0,02 y 0,35 ml m 3 -(promedio 0,10). Entre los promedios mensuales de densidad y biomasa seca de las estaciones no se encontró diferencia estadística significante, sin embargo se verificaron entre los promedios anuales. En los años 2003 y 2004 la densidad anual varió entre 27,74 y 52,44 ind m 3 y el peso seco entre 1,28 y 2,01 mg m 3 -mientras que en el 2005 fueron mayores los promedios de densidad (79,30 y 88,31 ind m 3 -) y de peso seco (2,17 y 2,69 mg m 3 ). Cinco grupos constituyeron el 81,78% del zooplancton nocturno, los copépodos representaron el 22,71%, el sergéstido Lucifer faxoni el 19,48%, los huevos y larvas de peces el 18,78%, los cladóceros Penilia y Podon el 18,10% y las zoeas de brachiura el 2,71%. La composición general del zooplancton difiere de otros estudios regionales, quizás por la alimentación de la sardina Sardinella aurita que abunda en el área estudio. Se mencionan valores de densidad promedio anual para cada grupo. En la estación Guacuco se encuentra una mayor y significativa abundancia de huevos y larvas de sardina, su densidad en los años 2002 y 2003 fueron mayores que en 2004 y 2005.
Zootaxa, 2010
A reassessment of the adult and larval morphology as well as comparison with published molecular ... more A reassessment of the adult and larval morphology as well as comparison with published molecular information confirms the monophyly of the genus Calyptraeotheres , and its relationship with Dissodactylus Smith, 1870, Clypeasterophilus Campos & Griffith, 1990 and Tumidotheres Campos, 1990. Calyptraeotheres pepeluisi new species, is described from Michoacán, Mexico on the basis of a female specimen. The new species is distinguished from the other nominal species of the genus by having a subarcuate carapace with longer setae on its front and anterolateral margin, the eyes are dorsally visible, and a third maxilliped with a 2-segmented palp and a conical propodus.
Zootaxa, 2007
Parapinnixa bolagnosi new species, is described from Cubagua Island and Los Frailes Archipelago i... more Parapinnixa bolagnosi new species, is described from Cubagua Island and Los Frailes Archipelago in the Caribbean Sea off Venezuela based on female specimens. The new species is distinguished from the other nominal species of the genus by having a ...
Zootaxa
All sipunculan species currently known to occur on the Caribbean coast of Venezuela and Curaçao a... more All sipunculan species currently known to occur on the Caribbean coast of Venezuela and Curaçao are reviewed. Included are species previously reported in the primary literature and those collected by Cutler (EBC) in 1987/1988 and Hernández-Ávila (IHA) in 2003/2004. Nineteen species of sipunculans belonging to eleven genera are known from this region. Most specious is the genus Aspidosiphon with seven species and the genus Phascolosoma with three species.
Proceedings of the Biological …, Jan 1, 2006
Calyptraeotheres hernandezi is described from off Cubagua Island, Caribbean Sea, Venezuela. The n... more Calyptraeotheres hernandezi is described from off Cubagua Island, Caribbean Sea, Venezuela. The new species resembles C. granti (Glassell, 1933) from the eastern Pacific, with both taxa possessing a third maxilliped with an endopod palp of only two segments, ie, ...
Bol. Inst. …, 2008
RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del micr... more RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del microfitoplancton de la Bahía de Charagato, relacionados con los cambios hidrográficos. Para ello fueron realizados muestreos mensuales determinando in situ la ...
Revista de biología tropical, 2013
Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, sub... more Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (C...
The crustacean decapod fauna of Cubagua Island in the Caribbean Sea, Venezuela, an island much af... more The crustacean decapod fauna of Cubagua Island in the Caribbean Sea, Venezuela, an island much affected by coastal upweling, was surveyed. A total of 178 species from 41 families were recorded, of which 56 species were new records for the island; eigth genera and six species were new records for Venezuela. Most species had previously been recorded from the the
Revista de biología marina y oceanografía, 2008
Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the... more Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the first record of N. antilocapra for Venezuela, and for the south Caribbean area. Nibilia antilocapra can be separated from other species of the family Epialtidae by the following features: wide postorbital tooth forming a cup, supraocular eave and postocular cup well separated, with a small tooth between them. Carapace pyriform, longer than wide, with several spines of different size on the surface. Chelipeds stouter than the walking leg, the formers diminish gradually in size. Four species of the subfamily Pisinae have been recorded for Venezuela marine waters.
Fertilized eggs from an spontaneously spawn of thirty sexually mature sea urchins (Arbacia punctu... more Fertilized eggs from an spontaneously spawn of thirty sexually mature sea
urchins (Arbacia punctulata) were incubated to complete embryonic development. The echinopluteus larvae
(3 ind/ml) were distributed into 50 plastic containers (25 containers at 30 psu and 25 containers at 40 psu) and
fed on Tetraselmis chuii, Nannochloropsis oculata, Isochrysis galbana, Chaetoceros gracilis and C. calcitrans
under a natural photoperiod. The water of the containers was partially renewed (75%) everyday. Larval anatomic
development aspects, daily survival and growth were determined. The growth was determined through postoral
arms and body length measurement, and body diameter of twelve larvae during metamorphosis. During the
planktonic larval phase, only the I. galbana diet produced similar results for both salinities. The relative growth
of larvae was isometric (I) for larvae fed on I. galbana at two salinities and positive allometric for those fed on
C. gracilis and C. calcitrans at both salinities. In this study A. punctulata started metamorphosis at day 14 and
was completed 30 days after fecundation. Significant differences were detected in post-settlement body growth
between the two salinities (F=23.58, p<0.05): growth was better for larvae at 30 psu (final body diameter was
3.14 ± 0.44 mm). The final rate of planktonic larvae was highest with I. galbana (58.33%). For juveniles the rate
was 6.48% for those fed on C. gracilis (40 psu in both larvae and juveniles). We recommend the use of this diet
and 40 psu for survival or 30 psu for growth
se incluyen los valores promedio de abundancia (ind/m 3 ) y la contribución acumulada de cada gru... more se incluyen los valores promedio de abundancia (ind/m 3 ) y la contribución acumulada de cada grupo (% cA).
Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagu... more Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagua Island, Venezuela. Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (Calyptraeidae) and Ophiotrix angulata (Ophiothrichidae) were the most common species found in these assemblages. The medium and high-density bivalve beds exhibited greater species number, abundance, Shannon diversity, evenness, taxonomic diversity, and taxonomic distinctness of associated fauna, than low-density bivalve beds. Moreover, multivariate analysis detected different assemblages of associated fauna between beds with different densities. Additionally, similarities were found in the communities of macrofauna in both beds of P. imbricata and Arca zebra. Our results suggest that bivalve aggregations at Cubagua Island provide additional habitat for macrofauna living in other shallow habitats such as Thalassia beds, corals and rocky environments. Bed density, associated with topographic complexity, represents an important factor for the composition and complexity of the associated fauna. Rev. Biol. Trop. 61 (2): 669-682. Epub 2013 June 01.
Beds of the Atlantic pearl oyster (Pinctada imbricata) and the turkey wing (Arca zebra) of contra... more Beds of the Atlantic pearl oyster (Pinctada imbricata) and the turkey wing (Arca zebra) of contrasting population densities were evaluated to determine the occurrence of associated decapod crustaceans. In these beds at Cubagua Island, Venezuela, we recorded 40 decapod species belonging to 18 families. Mithraculus forceps (Majidae), Pilumnus caribaeus (Pilumnidae), Cuapetes americanus (Palaemonidae) and Petrolisthes galathinus (Porcellanidae) were the most common species found in these assemblages. The medium-and high-density bivalve beds exhibited more species and a greater abundance of associated decapods than the low-density bivalve beds, and more taxonomic distinctness. Multivariate analysis detected different groups of decapods in the low-density beds and the medium-to high-density beds. Additionally, similarities were found in the communities of crustaceans in the beds of Atlantic pearl oysters and turkey wing, demonstrating that bed density is important for the composition of associated fauna. RESUMEN: Composición de ensambles de crustáceos decápodos en bancos de Pinctada imbricata y arca zebra (Mollusca: Bivalvia) en la Isla de Cubagua, Venezuela: Efecto de la densidad del banco. -Bancos de la ostra perla del Atlántico (P. imbricata) y de la pepitona (A. zebra) de densidades poblacionales contrastantes fueron evaluados para determinar la ocurrencia de crustáceos decápodos asociados. En estos bancos en la isla de Cubagua, Venezuela, fueron colectadas 40 especies de decápodos, pertenecientes a 18 familias. Mithraculus forceps (Majidae), Pilumnus caribaeus (Pilumnidae), Cuapetes americanus (Palaemonidae) y Petrolisthes galathinus (Porcellanidae) fueron las especies más comunes en estos ensambles. Los bancos de densidad media y alta mostraron mayor riqueza de especies y abundancia que los de baja densidad de bivalvos, así como mayor distinción taxonómica. Análisis multivariados detectaron diferentes grupos de decápodos en los bancos de baja densidad en relación a los de densidad media y alta. Adicionalmente, la fauna encontrada en bancos de ostra perla y pepitona no mostró diferencias, demostrando que la densidad es importante para la composición de la fauna asociada.
Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the... more Seven specimens of Nibilia antilocapra were collected in Margarita Island, Venezuela. This is the first record of N. antilocapra for Venezuela, and for the south Caribbean area. Nibilia antilocapra can be separated from other species of the family Epialtidae by the following features: wide postorbital tooth forming a cup, supraocular eave and postocular cup well separated, with a small tooth between them. Carapace pyriform, longer than wide, with several spines of different size on the surface. Chelipeds stouter than the walking leg, the formers diminish gradually in size. Four species of the subfamily Pisinae have been recorded for Venezuela marine waters.
RESUMEN: Durante un estudio bionómico de la isla de Cubagua fue colectado un espécimen de Tyche e... more RESUMEN: Durante un estudio bionómico de la isla de Cubagua fue colectado un espécimen de Tyche emarginata, lo cual constituye el primer registro para aguas venezolanas. El espécimen macho 22 mm longitud del caparazón) fue capturado entre rocas a 3,5 m de profundidad. Entre los caracteres diagnósticos se encuentran: Caparazón oblongo-oval, borde fronto-orbital poco menos el ancho del caparazón, con cuatro cuernos, dos submesiales paralelos y dos laterales divergentes. Región gástrica elevada, región cardíaca deprimida, con tres tubérculos cada una. Bordes laterales rectos en la región hepática, redondeados en la branquial. Región hepática cóncava. Tercer maxilípedo con una protuberancia basal en el exópodo que se proyecta sobre el isquio, margen interno del isquio fuertemente dentado. Longitud del quelípedo más del doble de la sección post-orbital del caparazón. El presente hallazgo es el primer registro del género en Venezuela, elevándose a 48 las especies de majoideos registrados en aguas venezolanas, cinco pertenecientes a la familia Tychidae.
RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del micr... more RESUMEN: En el presente trabajo se caracterizan los cambios en la estructura comunitaria del microfitoplancton de la bahía de Charagato, relacionados con los cambios hidrográficos. Para ello fueron realizados muestreos mensuales determinando in situ la temperatura y salinidad y colectando muestras a 0 y 5 m de profundidad a 100 m de la costa y a 0, 5, 10 y 20 m a 1 km, para determinar concentraciones de amonio, nitrito, nitrato, fosfato, clorofila a, feopigmentos y para los análisis cualitativos y cuantitativos del fitoplancton por el método Utermöhl. Además, fue determinada la dirección y la velocidad del viento. No fueron detectadas diferencias significativas tanto en la hidrografía y del fitoplancton entre las estaciones ni entre las profundidades estudiadas. Sin embargo, fueron observadas variaciones estacionales con menores temperaturas y mayores concentraciones de nutrientes en julio/2003 y durante enero-marzo/2004, que estuvieron asociadas al proceso de surgencia costera de la región. Se identificaron 320 especies de microfitoplancton, principalmente de diatomeas y dinoflagelados. Entre las más frecuentes y abundantes, se encontró: Nitszchia longissima, Pseudonitszchia delicatissima, Cylindroteca closterium, Thalassionema nitszchioides y Emiliana huxleyi. Las variaciones temporales de la composición y abundancia fitoplanctónica estuvieron asociadas a la ocurrencia estacional del proceso del surgencia, pero con un aparente desfase entre los procesos meteorológicos, hidrográficos y biológicos.
RESUMEN: En la costa este de Margarita durante 39 meses (2002)(2003)(2004)(2005) quincenalmente s... more RESUMEN: En la costa este de Margarita durante 39 meses (2002)(2003)(2004)(2005) quincenalmente se estudió la abundancia y composición del zooplancton nocturno en dos estaciones (Guacuco y Porlamar) localizadas a 5 millas de la costa. Se utilizo una red de plancton (diámetro de 1,7 m; longitud de 3,5 m; abertura de malla de 400 micras) arrastrada durante 20 minutos a profundidad de 10-15 m. Se encontraron representantes de 21 grupos y se contabilizaron 6.688.352 individuos. En Guacuco la densidad del zooplancton varió entre 6,28 y 385,91 ind m -3 (promedio 61,53), la biomasa seca entre 0,43 y 14,34 mg m -3 -(promedio 2,10) y el volumen sedimentado entre 0,02 y 0,70 ml m 3 -(promedio de 0,13). En Porlamar la densidad varió entre 7,55 y 537,78 ind m 3 -(promedio 49,11), la biomasa seca entre 0,26 y 4,63 mg m 3 -con (promedio 1,83) y el volumen sedimentado entre 0,02 y 0,35 ml m 3 -(promedio 0,10). Entre los promedios mensuales de densidad y biomasa seca de las estaciones no se encontró diferencia estadística significante, sin embargo se verificaron entre los promedios anuales. En los años 2003 y 2004 la densidad anual varió entre 27,74 y 52,44 ind m 3 y el peso seco entre 1,28 y 2,01 mg m 3 -mientras que en el 2005 fueron mayores los promedios de densidad (79,30 y 88,31 ind m 3 -) y de peso seco (2,17 y 2,69 mg m 3 ). Cinco grupos constituyeron el 81,78% del zooplancton nocturno, los copépodos representaron el 22,71%, el sergéstido Lucifer faxoni el 19,48%, los huevos y larvas de peces el 18,78%, los cladóceros Penilia y Podon el 18,10% y las zoeas de brachiura el 2,71%. La composición general del zooplancton difiere de otros estudios regionales, quizás por la alimentación de la sardina Sardinella aurita que abunda en el área estudio. Se mencionan valores de densidad promedio anual para cada grupo. En la estación Guacuco se encuentra una mayor y significativa abundancia de huevos y larvas de sardina, su densidad en los años 2002 y 2003 fueron mayores que en 2004 y 2005.