Abstract: The present article exposes a practice in the course “Ecology and Development” in a school of natural sciences. The objective is to promote the students’ appropriation of the campus space, the socio-environmental conflicts, and the concepts of socio-ecological systems. Through discussion and the use of aerial images, bibliographical information, journalistic notes, photographs and the narration of a member of the University Campus Community Plant Nursery, landscape changes and its uses are historically reconstructed. The work has led to the identification of different actors involved, a spatial visualization of the uses they make of space, and the identification of conflicts. This didactic and technical tool has proven to be a valuable device to facilitate dialogue among different actors.

Resumen: El presente trabajo expone una práctica de la materia “Ecología y Desarrollo” en el ámbito de una Facultad de ciencias naturales. El objetivo es fomentar la apropiación por parte del estudiantado del espacio del campus y de conceptos de conflictos socio-ambientales y sistemas socio-ecológicos. A través de un trabajo de debate y con el uso de imágenes aéreas, información bibliográfica, notas periodísticas, fotografías del lugar y el relato de un integrante del Vivero Comunitario Ciudad Universitaria, se reconstruyen históricamente los cambios en el paisaje y sus usos. Las dinámicas planteadas propiciaron la identificación de distintos actores involucrados, visualización espacial de los usos que estos hacen del espacio, y la identificación de diferentes conflictos. Esta herramienta didáctica y técnica resultó un dispositivo valioso para facilitar el diálogo entre distintos actores.

The dynamics of Enochrus variegatus (Steinheil) and Enochrus vulgaris (Steinheil) in temporary pools and permanent ponds were studied in an urban park of Buenos Aires, Argentina. Samples were collected from both types of habitats weekly throughout one year, and variables like water surface and vegetation cover were recorded. In permanent ponds, adults of both species were found throughout the study period, while in temporary pools their presence depended on the availability of water. Differences in their reproductive seasons and breeding sites were observed. Enochrus vulgaris was characterized by an opportunistic strategy, and its larvae were detected in both types of habitats, associated mainly with spring and summer temperatures. Conversely, E. variegatus larvae were recorded almost exclusively in temporary pools, during the winter and spring seasons. In permanent ponds, both species were associated with vegetation cover, which could be related to the availability of refuges from fish predators. First instar larvae showed the highest abundance and were captured more frequently, in consecutive weeks and simultaneously with third instar larvae, suggesting that the two populations studied are not synchronized in oviposition time or development of immature stages. In several occasions, second instar larvae of both species were captured in a pool that had been dry during the previous sampling date, suggesting that they had not hatched from fresh laid eggs. Our findings show that adults of these species are capable of dispersal to and from temporary pools to avoid drought. In addition, their larval stages may also be able to resist drought in the pools by burrowing into the substrate.

Se estudió la dinámica de Enochrus variegatus (Steinheil) y Enochrus vulgaris (Steinheil) en ambientes acuáticos temporarios y permanentes de un parque de Buenos Aires, Argentina. Las muestras fueron colectadas semanalmente a lo largo de un año en ambos tipos de ambiente, y se registraron variables como la superficie anegada y la cobertura vegetal. En los ambientes permanentes se capturaron ejemplares adultos de ambas especies a lo largo de todo el período de estudio, mientras que en temporarios su presencia varió de acuerdo con la disponibilidad de agua. Se observaron diferencias en la época reproductiva y sitios de cría de ambas especies. Enochrus vulgaris mostró una estrategia más oportunista, y sus larvas fueron detectadas en los dos tipos de ambiente asociadas principalmente con temperaturas de la primavera y el verano. En cambio las larvas de E. variegatus fueron registradas casi exclusivamente en cuerpos de agua temporarios durante el invierno y la primavera. En ambientes permanentes, ambas especies estuvieron asociadas con una mayor cobertura vegetal, lo cual podría estar relacionado con la disponibilidad de refugios de peces predadores. Para ambas especies el primer estadio larval fue colectado en mayor abundancia y frecuencia que los restantes. Las larvas de este estadio fueron registradas en semanas consecutivas y simultáneamente con larvas del tercer estadio, indicando que la oviposición o el desarrollo de los estadios inmaduros no estaban sincronizados dentro de cada una de las dos poblaciones estudiadas. En varias ocasiones se capturaron larvas del segundo estadio de ambas especies en charcos que estuvieron secos la fecha de muestreo anterior, sugiriendo que no eclosionaron de huevos recientemente puestos. Nuestros resultados muestran que los adultos de estas especies son capaces de dispersarse desde y hacia charcos temporarios para evitar la sequía, y que sus larvas podrían resistir la sequía en los ambientes temporarios enterrándose en el sustrato.

We present the results of the first survey on the aquatic and semiaquatic water beetles from the Ernesto Tornquist Provincial Park. The material was obtained from several quantitative samplings of aquatic insects covering all seasons from 2005 to 2007. The surveyed habitats were the Ventana, El Loro and Sauce Grande streams and two rain pools. A total of 5,200 specimens belonging to 9 families, 20 genera and 34 species of Coleoptera were identified. A list of the species known to occur in the park along with their distributional data in Argentina is presented. Twenty-three species are cited from the park for the first time. Austrelmis sp. and Hydrochus stolpi Germain are recorded for the first time from Buenos Aires Province.

Se presenta el primer relevamiento de coleópteros acuáticos y semiacuáticos del Parque Provincial Ernesto Tornquist. El material entomológico estudiado se obtuvo durante las campañas de recolección de insectos acuáticos, realizadas entre los años 2005 y 2007, en las cuatro estaciones del año. Los ambientes estudiados fueron los arroyos Ventana, El Loro, Sauce Grande y dos charcos temporarios. Se identificaron en total 5.200 ejemplares pertenecientes a 9 familias, 20 géneros y 34 especies. Se brinda el listado de las especies y su distribución en la Argentina. Se citan, por primera vez para el parque, 23 especies y por primera vez para la Provincia de Buenos Aires: Austrelmis sp. e Hydrochus stolpi Germain.

Background: In a previous study we reported that healthy children born at 34 or fewer gestational weeks, with adequate weight for gestational age, had not completed their bone catch-up at mean age of 6.3 years. Aim: This is a follow up report, performed on the same population one year later to determine at which age premature - born children achieve their bone mineral density (BMD) catch-up, compared to term-born controls. Material and methods: Fifteen children mean age 7years 3 months, born at 25 to 34 weeks of gestation, with a birth weight of 740 to 2.200 g were studied Radius, lumbar spine and femoral neck bone mineral density, whole body bone mineral content and body composition were assessed by DEXA. Results: Height, body mass index, peripheral BMD, axial BMD, fat and lean body mass in these children were not different from term born controls. Conclusions: Premature born children with adequate weight for gestational age, achieved peripheral and axial bone mineral density catch-up at the age of 7 to 8 years

We studied the effects of fire on the structural attributes of a Spartina densiflora salt marsh. The study was carried out from November 1995, spring (N95S) to December 1996, late spring (D96LS). In November 1995, we installed 37 permanent plots. In January 1996, 32 of the plots were accidentally burned (B) and the remaining were not burned (NB). Vegetation on each plot was sampled seasonally, plant species were identified and cover-abundance was estimated. We analyzed and compared seasonal variations in plant species richness, diversity, composition and cover-abundance in burned and non-burned plots. In addition, we analyzed variations in biological types (forbs, graminoids) and types of life cycles (annuals, perennials) in B and NB plots before and after the fire .Principal Component Analysis (PC A) was performed on cover-abundance data for each treatment and sampling date. We included coded dummy variables for each date and treatment as supplementary variables. Results indicated that S. densiflora was the dominant species and Limonium brasiliensis and Dipsacum fullonum were the accompanying species for all treatments and sampling dates. Thirty out of 47 species were present before the fire (N95S). All species in NB plots were also recorded in B plots, and 15 species were exclusively found in B plots. The increases in species richness and diversity observed in B plots after the fire were higher than those in NB plots at the same sampling dates. When comparing the B plots before and after the fire, perennials decreased in cover-abundance and increased in richness, while both attributes increased for annuals; the same pattern was followed by forbs, and graminoids decreased in cover abundance and showed almost similar values of richness. PCA results showed that NB plots were subject to smooth temporal changes in composition and cover abundance, and that B plots underwent greater changes. In D96LS, B and NB plots exhibited a different spatial distribution, which in turn differed from that observed in pre-fire plots in N95S

En este trabajo estudiamos el efecto del fuego sobre atributos estructurales de una marisma de Spartina densiflora. El estudio se realizó desde noviembre de 1995, primavera (N95P) hasta diciembre de 1996, primavera tardía (D96PT). En noviembre se instalaron 37 parcelas permanentes, en enero de 1996, 32 (Q) se quemaron accidentalmente mientras que cinco no (NQ). La vegetación de cada parcela fue muestreada estacionalmente. Las especies fueron identificadas y su cobertura-abundancia estimada. Analizamos y comparamos las variaciones estacionales en la riqueza específica, diversidad, composición y cobertura-abundancia en parcelas Q y NQ. Los tipos biológicos (latifoliadas y graminiformes) y de ciclos de vida (anuales y perennes) fueron comparados antes (N95P) y después del fuego (D96PT) en las parcelas Q y NQ. El análisis de componentes principales (PCA) se realizó en base a la cobertura-abundancia de las especies por parcela para cada fecha y tratamiento. La especie dominante fue S. densiflora. Las acompañantes Limonium brasiliense y Dipsacum fullanum estuvieron presentes en todas las fechas de muestreo y tratamientos. En total se identificaron 47 especies, 30 de las cuales estuvieron presentes antes del fuego. Todas las especies presentes en las parcelas NQ lo estuvieron en las Q en las cuales 15 especies fueron exclusivas de este tratamiento. Los incrementos en riqueza de especies y diversidad fueron mayores en las parcelas Q que en las NQ para las mismas fechas. Cuando las perennes se compararon en las parcelas Q antes y después del fuego, se encontró que disminuyeron en cobertura-abundancia e incrementaron su riqueza; mientras que ambos valores s incrementaron en las anuales, el mismo patrón siguieron las latifoliadas mientras que las graminiformes disminuyeron sus valores de cobertura-abundancia pero la riqueza permaneció similar. Los resultados del PC A mostraron que las parcelas NQ estuvieron sujetas a cambios temporales, en composición y cobertura-abundancia de las especies, menores que las Q y que en D96PT las parcelas Q y NQ mostraron una distribución espacial diferente de la observada en N95P

The immature stages of Ochlerotatus albifasciatus develop in temporary pools. The present study aims at evaluating the seasonal dynamics of the aquatic stages of this mosquito, also analyzing the relationship among their presence and breeding success to some relevant climatic and environmental variables in the ephemeral rain pools of an urban park. Nineteen cohorts of O. albifasciatus that developed synchronously after rain events were recorded in all seasons. The proportions of mosquito-positive pools were significantly higher during the fall-winter period than in the spring-summer months (p < 0.001). The presence of this mosquito species was positively related to the amount of rain (p < 0.001), whereas negatively correlated to air temperature (p < 0.05) within a 5.2 to 29.7ºC range. The distribution of the number of cohorts per pool throughout the year was grouped (variance/mean: 3.96), indicating that these habitats were not equally suitable as breeding sites. The immature stages of O. albifasciatus were detected in pools belonging to all of the categories of surface area, depth, duration, vegetation cover, and insolation. However, the proportion of pools where immature mosquitoes were detected was positively and significantly related to surface, depth, duration, and vegetation cover. On the other hand, the proportion of mosquito-positive pools was higher at an intermediate insolation degree. Our results suggest that although preimaginal stages were present in all seasons, high temperatures may be unfavorable to larval development, and substrate vegetation may regulate water temperature. The positive relationship between the proportion of mosquito-positive pools and pool size and duration might reflect a strategy of O. albifasciatus to accomplish immature development.

Aedes albifasciatus is a floodwater mosquito that breeds in temporary waters. This semi-domestic species, widely distributed in Argentina, is a competent vector of the western equine encephalitis. The present study was carried out in two rain pools of the city of Buenos Aires, from April 1998 through March 1999. Samples were taken twice a week during the cold season and daily during the warmer months, starting from October. Immature mosquitoes were collected with a dipper, being the number of dippers proportional to the flooded area. The estimated rainfall thresholds to initiate cohorts of Ae. albifasciatus were: 16-17 mm in the fall-winter period, 25 mm in the spring, and 30 mm in the summer. The development time of the different cohorts and the mean air temperature of their respective periods were estimated in all seasons, ranging from six days (at 24ºC) to 32 days (at 13ºC). The equation that best expresses the relationship between development time and mean air temperature is dt =166,27.e-0,1435.T (R²=0,92). Significantly shorter development times were recorded for larvae of the first three stages as compared to the fourth larval stage and pupae.