DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 1999
Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes... more Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp. and Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera) using different preservatives (Freezing, Formaldehyde 4% and Kahle). The organisms were collected monthly during a year on the Orituco river, Venezuela with a Surber net (0. 1296 m² and 0.286 mm mesh size). The data presented here are representative of the organism conditions year around. No attempt was made to quantify intersample variation. Regression analysis indicated that all relationships were highly correlated for any of the fixatives used. Changes in dry mass per unit change of head capsule width, vary among species and preservatives with no clear relationship among them. Changes in dry mass calculated as the difference between dry mass of preserved samples to those of unpreserved ones, indicate that all fixatives underestimate dry mass by as much as 85.4%, except for Nectopsyche sp. whose dry mass was always overestimated. These results provide further evidence on the effect of preservatives on dry mass losses. Even when working with tropical species, any study in which biomass is going to be determined should consider the effect of preservatives on dry mass.<br>Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Nectopsyche sp. (Trichoptera) y Anacroneuria sp. (Plecoptera) usando diferentes preservativos (Congelamiento, Formol 4% and Kahle). El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa obtenidos con los diferentes preservativos y los obtenidos con muestra [...]
Trends in Research in Ephemeroptera and Plecoptera, 2001
The composition, seasonal variation and diversity of the mayfly fauna in four streams (two waters... more The composition, seasonal variation and diversity of the mayfly fauna in four streams (two watersheds) of the Guatopo National Park were studied biweekly for one year (February 1996-February 1997). The density of the Ephemeroptera has a distinctive cycle with maximum abundance at the middle of the dry season and minimum during the rainy season. The abundance of this community is significantly different among rivers belonging to different watersheds. The Leptophlebiidae (Thraulodes sp.) was always the most abundant family, in all rivers, followed by the Leptohyphiidae. However, the latter showed a higher diversity than the former. Principal Component Analysis of the data indicated that the community structure of the mayfly fauna is more similar among rivers belonging to the same watershed regardless of differences in morphometric variables of the streams.
In order to estimate secondary production of aquatic insects, the number of generations by year (... more In order to estimate secondary production of aquatic insects, the number of generations by year (univoltine or multivoltine) must be established. Secondary production of organisms with univoltine life cycles is usually calculated using cohorr analysis (BENKE 1979). On the other hand, in organisms with asynchronous development and fast growth rate, a cohort cannot be identified; in these cases life-cyde duratian or growth rate have to be known in order to calculate secondary production (B ENKE & ]ACOBI 1986, BENKE 1993). There is some evidence to support the assumption that tropical aquatic insects are polyvoltine (e.g. ]ACKSON & SWEENEY 1995). Therefore, as part of a study on the secondary production of the benthic community of the River eamurí Grande, the development time and growth rate of the main components of the macroinverrebrate community were determined. Trichoptera, Ephemeroptera and Diptera comprise 83.6% of the benthic community in the R. eamurí Grande, with Trichoptera representing 36.7% (eREsSA 1998), indicating that this order must play an important role in the secondary production in this river. For this reason, trichopterans were the first organisms for which growth rates and development time were calculated, and in this paper the growth rate and life cycle of two species: Helicopsyche sp. (Helicopsychidae) and Nectopsyche gemmoides (Leptoceridae) were examined under laboratory conditions.
Relationships of body mass and head capsule width were developed for Thraulodes sp., Haplohyphes ... more Relationships of body mass and head capsule width were developed for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Phylloicus sp. Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera). The organisms were collected with a Surber net (0.1296 m2 and 0.286 mm mesh size) on the Orituco river, Venezuela. The number of specimens used in the analysis for the species studied, was different (from 84 to 103 specimens). Regression analysis indicated that all relationships were best expressed by a power function rather than by linear or exponential equation. Analyses of the relationships reveal interspecific differences among insects of the same order. Species-specific relationships are recommended to be used whenever possible since, depending on the species, the underestimation of mass could be as much as 56%.
Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsul... more Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Nectopsyche sp. (Trichoptera) y Anacroneuria sp. (Plecoptera) usando diferentes preservativos (Congelamiento, Formol 4% and Kahle). El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa obtenidos con los diferentes preservativos y los obtenidos con muestras no preservadas, indica que todos los preservativos subestiman la masa seca hasta en un 85,4%, excepto en el caso de Nectopsyche sp. cuya masa corporal fue siempre sobre-estimada. Los resultados presentados en este trabajo nuevamente indi...
Population density, diurnal vertical distribution and secondary production of limnetic Chaoborus ... more Population density, diurnal vertical distribution and secondary production of limnetic Chaoborus larvae were studied during the dry and the rainy season. Population density was high (3,667-24,220 individuals/m 2 ) and showed maximum values during the dry season. Larvae cycle was about 48 days. The highest percentage of biomass and production was due to older instars. These trends and values observed are similar to those reported for tropical eutrophic lakes. Also a vertical segregation of larvae in the water column was observed with early instars located nearer to the surface than older instars. While the mean depth of early instars was related to light, older instars position was associated to light, oxygen and food.
ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases dur... more ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases during the dry and rainy seasons in a neotropical intermittent stream in Northwestern Venezuela. Invertebrates and physicochemical parameters were sampled during 9 months to assess temporal changes in biotic and abiotic variables. Macroinvertebrate densities decreased following either a high-flow or a stream drought. Three invertebrate assemblages were identified via PCA and cluster analysis. PCA ordination showed a temporal sequence between the sampling dates. A low flow association occurred in August, a period of rewetting after the stream drought in late July. A high-flow association was established by sampling dates (September and November) with the highest flows registered during the study, and an intermediate-flow association occurred during the longer dry period after the rainy season. The low-flow group was dominated by the Philopotamidae (65 %). The intermediate-flow group showed a more even distribution of macroinvertebrate abundances. The high-flow group was dominated by Philopotamidae, Leptophlebiidae, Chironomidae and Baetidae. The lowest richness and highest density values were observed for the low-flow group. Average physicochemical parameters also were different between the PCA groups. A gradient of physicochemical parameters was observed from the &#39;low-flow&#39; group to the &#39;high-flow&#39; group. Temporal flow changes probably structure macroinvertebrate communities during extreme episodes of drought or spates, but during intermediate flow periods some biotic processes may determine community structure.
Thesis (Ph. D.)--University of Colorado, 1985. Includes bibliographical references (leaves [142]-... more Thesis (Ph. D.)--University of Colorado, 1985. Includes bibliographical references (leaves [142]-160).
... Onchocerciasis (river blindness) control programs in tropical Africaespecially West Africah... more ... Onchocerciasis (river blindness) control programs in tropical Africaespecially West Africahave resulted in the recognition of over 193 species (Shelley, 1988) in habitats ranging from torrential streams to the carapaces of freshwater crabs and prawns (Williams and Hynes ...
Notalina roraima Holzenthal 1986 was described on the basis of a single holotype specimen from th... more Notalina roraima Holzenthal 1986 was described on the basis of a single holotype specimen from the Pantepui Region. The species is a member of the endemic Neotropical long-horned caddisfly (Trichoptera: Leptoceridae) subgenus Notalina (Neonotalina) Holzenthal 1986. We present new records of this species and describe some morphological variation in the male genitalia. Moreover, we describe and illustrate the larva of this species and include information of its habitat. We also differentiate it from N. morsei, the only larva of the subgenus Neonotalina described until now.
Journal of the North American Benthological Society, 2003
We collected an undescribed hydropsychid caddisfly, Smicridea (Smicridea) travertinera, n. sp., f... more We collected an undescribed hydropsychid caddisfly, Smicridea (Smicridea) travertinera, n. sp., from 2 sites in Venezuela. One of the sites, Quebrada El Charo, flowed over extensive calcareous formations of travertine, which were covered with retreats and capture nets of the new species. Smicridea travertinera was the most abundant aquatic insect colonizing travertine. We describe the adult male, the retreat and net, and gut contents. The retreat consisted of an aperture in the travertine with a capture net. Retreat-making behavior appears to cause both the biogenesis and erosion of the travertine formations.
DOAJ (DOAJ: Directory of Open Access Journals), Jun 1, 1999
Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes... more Relationships of body mass and head capsule width were calculated for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp. and Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera) using different preservatives (Freezing, Formaldehyde 4% and Kahle). The organisms were collected monthly during a year on the Orituco river, Venezuela with a Surber net (0. 1296 m² and 0.286 mm mesh size). The data presented here are representative of the organism conditions year around. No attempt was made to quantify intersample variation. Regression analysis indicated that all relationships were highly correlated for any of the fixatives used. Changes in dry mass per unit change of head capsule width, vary among species and preservatives with no clear relationship among them. Changes in dry mass calculated as the difference between dry mass of preserved samples to those of unpreserved ones, indicate that all fixatives underestimate dry mass by as much as 85.4%, except for Nectopsyche sp. whose dry mass was always overestimated. These results provide further evidence on the effect of preservatives on dry mass losses. Even when working with tropical species, any study in which biomass is going to be determined should consider the effect of preservatives on dry mass.<br>Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Nectopsyche sp. (Trichoptera) y Anacroneuria sp. (Plecoptera) usando diferentes preservativos (Congelamiento, Formol 4% and Kahle). El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa obtenidos con los diferentes preservativos y los obtenidos con muestra [...]
Trends in Research in Ephemeroptera and Plecoptera, 2001
The composition, seasonal variation and diversity of the mayfly fauna in four streams (two waters... more The composition, seasonal variation and diversity of the mayfly fauna in four streams (two watersheds) of the Guatopo National Park were studied biweekly for one year (February 1996-February 1997). The density of the Ephemeroptera has a distinctive cycle with maximum abundance at the middle of the dry season and minimum during the rainy season. The abundance of this community is significantly different among rivers belonging to different watersheds. The Leptophlebiidae (Thraulodes sp.) was always the most abundant family, in all rivers, followed by the Leptohyphiidae. However, the latter showed a higher diversity than the former. Principal Component Analysis of the data indicated that the community structure of the mayfly fauna is more similar among rivers belonging to the same watershed regardless of differences in morphometric variables of the streams.
In order to estimate secondary production of aquatic insects, the number of generations by year (... more In order to estimate secondary production of aquatic insects, the number of generations by year (univoltine or multivoltine) must be established. Secondary production of organisms with univoltine life cycles is usually calculated using cohorr analysis (BENKE 1979). On the other hand, in organisms with asynchronous development and fast growth rate, a cohort cannot be identified; in these cases life-cyde duratian or growth rate have to be known in order to calculate secondary production (B ENKE & ]ACOBI 1986, BENKE 1993). There is some evidence to support the assumption that tropical aquatic insects are polyvoltine (e.g. ]ACKSON & SWEENEY 1995). Therefore, as part of a study on the secondary production of the benthic community of the River eamurí Grande, the development time and growth rate of the main components of the macroinverrebrate community were determined. Trichoptera, Ephemeroptera and Diptera comprise 83.6% of the benthic community in the R. eamurí Grande, with Trichoptera representing 36.7% (eREsSA 1998), indicating that this order must play an important role in the secondary production in this river. For this reason, trichopterans were the first organisms for which growth rates and development time were calculated, and in this paper the growth rate and life cycle of two species: Helicopsyche sp. (Helicopsychidae) and Nectopsyche gemmoides (Leptoceridae) were examined under laboratory conditions.
Relationships of body mass and head capsule width were developed for Thraulodes sp., Haplohyphes ... more Relationships of body mass and head capsule width were developed for Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Phylloicus sp. Nectopsyche sp. (Trichoptera), and Anacroneuria sp. (Plecoptera). The organisms were collected with a Surber net (0.1296 m2 and 0.286 mm mesh size) on the Orituco river, Venezuela. The number of specimens used in the analysis for the species studied, was different (from 84 to 103 specimens). Regression analysis indicated that all relationships were best expressed by a power function rather than by linear or exponential equation. Analyses of the relationships reveal interspecific differences among insects of the same order. Species-specific relationships are recommended to be used whenever possible since, depending on the species, the underestimation of mass could be as much as 56%.
Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsul... more Se calcularon las ecuaciones para las relaciones entre la masa del cuerpo y el ancho de la cápsula cefálica para Thraulodes sp., Haplohyphes sp. (Ephemeroptera), Leptonema sp., Nectopsyche sp. (Trichoptera) y Anacroneuria sp. (Plecoptera) usando diferentes preservativos (Congelamiento, Formol 4% and Kahle). El análisis de regresión indicó que todas las relaciones obtenidas son altamente significativas para cada uno de los preservativos utilizados. Los cambios en la masa del cuerpo por unidad de cambio en el ancho de la cápsula cefálica, son diferentes para cada especie y preservativo, sin haberse obtenido una clara relación entre ellos. La compararación entre los valores de masa obtenidos con los diferentes preservativos y los obtenidos con muestras no preservadas, indica que todos los preservativos subestiman la masa seca hasta en un 85,4%, excepto en el caso de Nectopsyche sp. cuya masa corporal fue siempre sobre-estimada. Los resultados presentados en este trabajo nuevamente indi...
Population density, diurnal vertical distribution and secondary production of limnetic Chaoborus ... more Population density, diurnal vertical distribution and secondary production of limnetic Chaoborus larvae were studied during the dry and the rainy season. Population density was high (3,667-24,220 individuals/m 2 ) and showed maximum values during the dry season. Larvae cycle was about 48 days. The highest percentage of biomass and production was due to older instars. These trends and values observed are similar to those reported for tropical eutrophic lakes. Also a vertical segregation of larvae in the water column was observed with early instars located nearer to the surface than older instars. While the mean depth of early instars was related to light, older instars position was associated to light, oxygen and food.
ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases dur... more ABSTRACT Changes in macroinvertebrate assemblages were identified among different flow phases during the dry and rainy seasons in a neotropical intermittent stream in Northwestern Venezuela. Invertebrates and physicochemical parameters were sampled during 9 months to assess temporal changes in biotic and abiotic variables. Macroinvertebrate densities decreased following either a high-flow or a stream drought. Three invertebrate assemblages were identified via PCA and cluster analysis. PCA ordination showed a temporal sequence between the sampling dates. A low flow association occurred in August, a period of rewetting after the stream drought in late July. A high-flow association was established by sampling dates (September and November) with the highest flows registered during the study, and an intermediate-flow association occurred during the longer dry period after the rainy season. The low-flow group was dominated by the Philopotamidae (65 %). The intermediate-flow group showed a more even distribution of macroinvertebrate abundances. The high-flow group was dominated by Philopotamidae, Leptophlebiidae, Chironomidae and Baetidae. The lowest richness and highest density values were observed for the low-flow group. Average physicochemical parameters also were different between the PCA groups. A gradient of physicochemical parameters was observed from the &#39;low-flow&#39; group to the &#39;high-flow&#39; group. Temporal flow changes probably structure macroinvertebrate communities during extreme episodes of drought or spates, but during intermediate flow periods some biotic processes may determine community structure.
Thesis (Ph. D.)--University of Colorado, 1985. Includes bibliographical references (leaves [142]-... more Thesis (Ph. D.)--University of Colorado, 1985. Includes bibliographical references (leaves [142]-160).
... Onchocerciasis (river blindness) control programs in tropical Africaespecially West Africah... more ... Onchocerciasis (river blindness) control programs in tropical Africaespecially West Africahave resulted in the recognition of over 193 species (Shelley, 1988) in habitats ranging from torrential streams to the carapaces of freshwater crabs and prawns (Williams and Hynes ...
Notalina roraima Holzenthal 1986 was described on the basis of a single holotype specimen from th... more Notalina roraima Holzenthal 1986 was described on the basis of a single holotype specimen from the Pantepui Region. The species is a member of the endemic Neotropical long-horned caddisfly (Trichoptera: Leptoceridae) subgenus Notalina (Neonotalina) Holzenthal 1986. We present new records of this species and describe some morphological variation in the male genitalia. Moreover, we describe and illustrate the larva of this species and include information of its habitat. We also differentiate it from N. morsei, the only larva of the subgenus Neonotalina described until now.
Journal of the North American Benthological Society, 2003
We collected an undescribed hydropsychid caddisfly, Smicridea (Smicridea) travertinera, n. sp., f... more We collected an undescribed hydropsychid caddisfly, Smicridea (Smicridea) travertinera, n. sp., from 2 sites in Venezuela. One of the sites, Quebrada El Charo, flowed over extensive calcareous formations of travertine, which were covered with retreats and capture nets of the new species. Smicridea travertinera was the most abundant aquatic insect colonizing travertine. We describe the adult male, the retreat and net, and gut contents. The retreat consisted of an aperture in the travertine with a capture net. Retreat-making behavior appears to cause both the biogenesis and erosion of the travertine formations.
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