Diversity in soil fungi from undisturbed and disturbed Celtis tala and Scutia buxifolia forests in the eastern Buenos Aires province (Argentina)

The rhizospheric soil microfungi from a native forest (undisturbed and disturbed) were studied using soil dilution plate and soil washing methods. Fungi were isolated using slightly acid and alkaline culture media. 54 taxa were isolated: 49 from undisturbed forest soil and 37 from disturbed forest soil. Acremonium sp., Aspergillus ustus, Coemansia pectinata, Doratomyces stemonitis, Fusarium solani, F. oxysporum, Gliocladium roseum, Humicola fusco-atra, Mortierella sp., Penicillium lilacinum, Trichoderma harzianum, and T. koningii, showed the highest frequency, in both, undisturbed and disturbed forests. In undisturbed soil forest the biodiversity index was 3.97 whereas in disturbed ones was 3.89.     

Population seasonality of the inmature stages of Aedes albifasciatus (Diptera: Culicidae) in Buenos Aires province, Argentina

Aedes albifasciatus, a floodwater mosquito, is widely distributed in freshwater habitats in Argentina. At high population densities it is an important pest in urban areas. A two year study was conducted in a natural population of A. albifasciatus around La Plata area, Buenos Aires province, Argentina. The breeding site was weekly sampled from May, 1996 to April, 1998. Immature stages of A. albifasciatus were collected with a standard 300 ml dipper. Each sample unit consisted of 100 dipper. Highest densities of mosquito larvae occurred when the breeding site was flooded among 90 and 100% of its capacity after remaining dry for several days or weeks. The larvae required between six and eight days to become adult in summer (temperature mean 24.6 degrees C in January and 21.3 degrees C in February). In autumn-winter, 43 days (temperature mean 10.6 degrees C) and in spring 22 days (temperature mean 15.5 degrees C).     

A new species of Tullbergia (Collembola,Tullbergiidae) from Buenos Aires,Argentina

A new species of Tullbergia from Argentina is described and illustrated; it is differentiated from Tullbergia paranensis by the number of vesicles of postantennal organ, pseudocelli shape and its formulae and the number of dorsal sensilla on Ant. IV. In addition a key for the identification of the members of the family from Argentina is included.     

A new giant cypridid ostracod (Crustacea) from southern Buenos Aires Province,Argentina

Amphicypris argentinensis sp. nov., is described and illustrated from Laguna Caliba, an ephemeral fresh water lake from the southern coast of Buenos Aires Province, Argentina. Specimens were raised from dried sediment recovered from a bank of ostracod shells found at the edges of the lake. Deposition of progressively smaller ostracod valves stacked one into another (cup-in-cup structure) is documented. The geographical distribution and ecology of the genus is briefly discussed.     

A new giant cypridid ostracod (Crustacea) from southern Buenos Aires Province, Argentina

Amphicypris argentinensis sp. nov., is described and illustrated from Laguna Caliba, an ephemeral fresh water lake from the southern coast of Buenos Aires Province, Argentina. Specimens were raised from dried sediment recovered from a bank of ostracod shells found at the edges of the lake. Deposition of progressively smaller ostracod valves stacked one into another (cup-in-cup structure) is documented. The geographical distribution and ecology of the genus is briefly discussed.     

Frequency of the Mating-Type (MAT1) in Histoplasma capsulatum Isolates from Buenos Aires,Argentina

Sex is genetically determined in Histoplasma capsulatum, governed by a sex-specific region in the genome called the mating-type locus (MAT1). We investigate the distribution of isolates of two H. capsulatum mating types in the clades circulating in Buenos Aires, Argentina. Forty-nine H. capsulatum isolates were obtained from the culture collection of the Mycology Center. The MAT1 locus was identified by PCR from the yeast suspension. The analysis of forty-eight isolates from clinical samples exhibited a ratio of 1.7 (MAT1-1:MAT1-2) and the only isolate from soil was MAT1-1. Forty-five H. capsulatum isolates belonged to the LAm B clade (H. capsulatum from Latin American group B clade) and showed a ratio of 1.8 (MAT1-1:MAT1-2). These results suggest an association between the mating types in isolates belonging to the LAm B clade. It remains to be defined whether a greater virulence should be attributed to the differences between the strains of the opposite mating type of the LAm B clade.

     

Airborne pollen sampling in a wildlife reserve in the south of Buenos Aires province,Argentina

The objective of this project was to study the pollen spectrum of the Marahué Wildlife Reserve (Central Argentina), the quantity and quality of airborne pollen grains, and to evaluate the contribution of outside sources, to protect a natural habitat with xerophytic shrub vegetation (“monte”) (the term “monte” is used for the dominant xerophytic shrub vegetation in the “partido” of Villarino) approximately 90 km south of Bahía Blanca. Sampling was performed weekly throughout a whole calendar year (January–December, 2003) using a volumetric impact sampler. Observations of flowering in the field were performed at the same time as the aerial sampling. Herbarium specimens were collected to make pollen collections of the species found in the study area, for reference purposes. The most abundant pollen types were Poaceae (31.3% total annual pollen), Amaranthus/Chenopodiaceae (25.3%), Eucalyptus (5%), Brassicaceae (3.9%), and Plantago (3.9%). This study showed the dispersion dynamics of pollen grains from characteristic species of the “partido” (the province of Buenos Aires is divided into partidos which are roughly equivalent to counties) of Villarino, the exotic flora of the surrounding area, and the pollen types from outside the region.

Atmospheric control of Aedes aegypti populations in Buenos Aires (Argentina) and its variability

The mosquito Aedes aegypti is the main urban vector responsible for the transmission of dengue fever and dengue hemorrhagic fever. The city of Buenos Aires, Argentina, is located at the southern end of the world distribution of the species. The population abundance of Ae. aegypti is mainly regulated by environmental factors. We calculated the potential number of times that a female could lay eggs during its mean life expectancy, based on potential egg production and daily meteorological records. The model considers those variables implying physical hazard to the survival of Ae. aegypti, mosquito flying activity and oviposition. The results, obtained after calibration and validation of the model with field observations, show significant correlation (P<0.001) for different lags depending on the life stage. From these results, more favorable atmospheric conditions for Ae. aegypti reproduction (linked to the urban climatic change) can be observed. The climatic variability in the last decade resembles conditions at the end of 19th century. Received: 3 March 1999 / Revised: 24 November 1999 / Accepted: 24 January 2000     

A new species of Brevilegnia (Saprolegniales, Straminipila) from Buenos Aires Province, Argentina

Brevilegnia ensenadensis sp. nov. is described from litter (floating twigs, leaves, and roots) in a man-made, polluted channel near a petroleum refinery, in Buenos Aires Province, Argentina. The species is illustrated and compared with other species of the genus; it can be identified by the preponderance of smooth or papillate oogonia, with a distinctive irregular inner wall, borne in bent or coiled oogonial stalks, which are terminal, lateral or of the intercalary position. The oogonia often are irregular in shape, and the oospheres mostly are immature. The single oospore is eccentric inside the great oogonia, and the species develops mainly diclinous antheridial branches and has fewer monoclinous and androgynous ones.     

Trajectories associated to regional and extra-regional pollen transport in the southeast of Buenos Aires province, Mar del Plata (Argentina)

Long range transport of airborne pollen has been seldom studied in South America. Backward trajectories of Celtis and Nothofagus pollen grains trapped over a meteorological station outside Mar del Plata City were calculated in one-hour steps using the regional hybrid model developed by the NOAA (HYSPLIT 4.5) and the data of the NCEP filed in the NOAA server. Results showed that the observed trajectories agree with the location of vegetation sources of the collected tree species. In the case of Celtis, the transport was associated to anticyclones located east of the city, generating winds with a N-NE component, which produce pollen cloud advection from the Celtis forests located some tens of kilometers to the N and NE of the city. The sources of Nothofagus pollen correspond to a narrow strip on the Andes slopes between 39° and 55°S, at least 1100 km to the SW of Mar del Plata. The transport was associated to eastward displacement of the troughs corresponding to the Westerlies circulation and the presence of an anticyclone system that brings back Nothofagus pollen towards Mar del Plata area.     

A comparative analysis of the phytoplankton from six pampean lotic systems (Buenos Aires, Argentina)

Phytoplankton, as well as physical and chemical variables of six lotic systems of Buenos Aires province, tributaries of Río de la Plata river (Rodríguez, El Gato, El Pescado, Buñirrigo and J. Blanco streams, Samborombón river) were analysed and results were related to the degree of anthropic pollution. Surveys were carried out seasonally from May 1997 to June 1998. Sample sites were stablished at 2 or 3 stations depending on the length of the systems, from the headwaters to the mouths. Specific composition, species richness, dominance, diversity and eveness were assessed. Diatoms and clorophytes presented the highest number of species. Cyanobacteria were dominant in 60% of the samples and diatoms were subdominant in 42% of them. Samborombón river showed minimun and maximun phytoplankton densities among the six systems (50 cell.ml^–1 and 188475 cell.ml^–1, respectively). Indexes values showed a non-defined pattern, increasing or decreasing in the most polluted sites. The first axis of the PCA which included the physical and chemical variables is characterized by the nutrient concentrations and it is related to the pollution of these systems, separating samples of Rodríguez and El Gato streams, which presented high positive scores, from the rest of them. The second axis is represented by variables which determine the water conductivity and separates samples from the mouths of Samborombón river and Buñirrigo stream, which presented high positive scores, from the rest of them. The species PCA indicate that its distribution is related to the first two components of the chemical data set PCA. The first axis separates species found in high-conductivity sites, such as the mouths of Samborombón and Buñirrigo systems (i.e. Cocconeis placentula, Aulacoseira granulata, Melosira varians, Actinocyclus normanii, Dictyosphaerium ehrenbergianum) from those registered in low-conductivity sites, such as J. Blanco stream (i.e. Pseudanabaena catenata, Nitzschia gracilis, Mallomonas sp.). The second axis separates and mesosaprobic species from polluted sites -Rodríguez and El Gato streams- (i.e. Gomphonema parvulum, Navicula cryptocephala, Nitzschia palea, N. umbonata, Oscillatoria amphibia, Lyngbya limnetica, Euglena acus) from those found in oligosaprobic non-polluted sites – J. Blanco stream – (Nitzschia gracilis, Pseudanabaena catenata, Gomphonema clavatum).     

Rodent control at different spatial scales on poultry farms in the province of Buenos Aires,Argentina

In poultry farms of central Argentina rodents cause economic losses by the consumption and contamination of chicken food, and also pose a serious sanitary risk as transmitters of several diseases to human and domestic animals, such as leptospirosis, salmonellosis, trichinosis, hantavirus pulmonary syndrome, hantavirus renal syndrome, and Argentine hemorrhagic fever. Because one of the problems in controlling rodents is recolonization from the surroundings, we wanted to assess the effect of control measures applied at different spatial scales on rodent abundance in farm sheds. The treatments applied were the following: anticoagulant application in farms and their surroundings (F + S), anticoagulant application only within farms (F), and standard management (C). Rodent abundance was assessed previous to treatments (t₀), at the moment of bait removal (t₁), and after 15 (t₂), 30 (t₃), and 60 days (t₄). Differences in rodent abundance between t₀ and t₁, t₂, t_3, and t₄ were compared among treatments by means of a Kruskal Wallis test. We only found significant differences among treatments between t₀ and t₂, where F and F + S treatments showed differences with respect to the C treatment. This result suggests that the effect of control measures was due to the control of the perimeter, and not of farther areas. Also, reproduction of remaining individuals may have contributed to the population recovery in sheds of experimental farms. We conclude that more effective control must include the perimeter of the farm, but the effect of control of more distant areas may depend on the characteristics of the particular farm, its surroundings, and the ecology of the species involved.     

New Dalyelliidae (Platyhelminthes, Rhabditophora) from Buenos Aires Province, Argentina, and their stylet ultrastructure

Two new species of Dalyellidae, Dalyellia callvucurai n. sp. and Gieysztoria namuncurai n. sp., are described from temporary freshwater environments in central Buenos Aires Province, Argentina. The ultrastructure of the stylets of both species is also described. The new species of the genus Dalyellia is the second species of the genus found in the neotropics and the first whose stylet has been studied with scanning electron microscopy. Gieysztoria namuncurai n. sp. joins the seven species of the genus known in Argentina. The ultrastructural characteristics of the stylet place it in the Inaequales group, with complex stylets.     

Diversity of understory plants in undisturbed and disturbed tropical lowland forests of Little Andaman Island, India

Species richness and density of understory plants were investigated in eight 1 ha plots, distributed one each in undisturbed and disturbed tropical evergreen, semi-evergreen, deciduous and littoral forests of Little Andaman island, India, which falls under one of the eight hottest hotspots of Biodiversity in the world viz. the Indo-Burma. One hundred 1 m⁻² quadrats were established in each 1 ha plot, in which all the understory plants (that include herbs, undershrubs, shrubs and herbaceous climbers) were enumerated. The total density of understory plants was 6,812 individuals (851 ha⁻¹) and species richness was 108 species, representing 104 genera and 50 families. Across the four forest types and eight study plots, the species richness ranged from 10 to 39 species ha⁻¹. All the disturbed sites harbored greater number of species than their undisturbed counterparts. Herbs dominated by species (63%) and density (4,259 individuals). The grass Eragrostis tenella (1,860 individuals; IVI 40), the invasive climber Mikania cordata (803; IVI 20) and the shrub Anaxagorea luzonensis (481; IVI 17.5) were the most abundant species. Poaceae, Asteraceae, Acanthaceae, Orchidaceae and Euphorbiaceae constituted the species-rich families represented by 6 species each. The species-area curves attained an asymptote at 0.8 ha level except in sites DD and DL, indicating 1 ha plot is not sufficient to capture all the understory species in disturbed forests. The alien weeds formed about one-fourth of the species richness (31 species; 28%) and density (1,926 individuals; 28.3%) in the study sites, indicating the extent of weed invasion and the attention required for effective conservation of the native biodiversity of the fragile island forest ecosystem.     

Sexual dimorphism in schoolchildren of the Villa IAPI neighborhood (Quilmes,Buenos Aires,Argentina)

Villa IAPI is a poor neighborhood of about 5,000 inhabitants in the overpopulated conurbano bonaerense at the outskirts of the city of Buenos Aires. Most of the adult male residents are construction workers; the rest are temporary workers, underemployed, or unemployed. The inhabitants of Villa IAPI suffer the effects of many adverse socio-economic conditions, including poor nutrition, deficient sanitation, and inadequate medical care. Seven anthropometric variables were measured on 765 children from 6 to 14 years old to test for the presence of an altered pattern of sexual dimorphism. It was found that there were practically no sex differences in standing height and upper-arm muscle circumference. In some age groups, there was a weak but significant sexual dimorphism in body weight and sitting height. The greatest and most persistent dimorphism was found in head circumference, and in triceps and subscapular skinfolds. In all except two age groups, head circumference in males was significantly greater than in females. The other dimorphic variables (body weight, sitting height, and triceps and subscapular skinfolds) showed the opposite relationship. Essentially, females showed increments in subcutaneous fat, while reduced growth in muscle and bone was evident in males. The hypothesis of “better female canalization” can explain the altered dimorphic pattern found in the malnourished Villa IAPI population. © 1993 Wiley-Liss, Inc.     

Description of a new Capillariinae (Nematoda: Trichuridae) from Scapteromys aquaticus (Cricetidae: Sigmodontinae) from Buenos Aires, Argentina

A new species of Capillaria is described on the basis of specimens recovered from the intestine of the swamp rat Scapteromys aquaticus (Cricetidae: Sigmodontinae) from Argentina. Capillaria alainchabaudi n. sp. and a peculiar species from Australian marsupials are the only 2 species of Capillaria sensu stricto parasitic in mammals. A comparison with the Australian species and with the 18 species of this genus described from other vertebrates from the Western Hemisphere is given. The separation of the new species is based on morphologic and morphometrical features, such as intestine ending in cloaca beside ejaculatory duct, 2 lateral nonmembranous caudal lobes, 2 pairs of caudal non-pedunculated papillae, terminal part of cylindrical cirrus ornamented with thin and thick spines, spicule with apex not well sclerotized in the males, a conspicuous vulvar appendage in the females, and 2 bacillary bands. A survey of the literature revealed that the species of Capillariinae from rodents belong to 9 genera, and the total number of species is low compared to the high diversity and abundance of the hosts, particularly if the modern Muroidea are considered.     

Wild bees (Hymenoptera: Apoidea) in an urban botanical garden in Buenos Aires,Argentina

We assessed bee diversity and abundance in a botanical garden in the city of Buenos Aires during two consecutive spring–summer periods. Every 15 days, we collected by hand-netting bee specimens seen foraging on flowers during five-minute censuses at every entomophilous herbaceous plant. A total of 66 bee species (Hymenoptera: Apoidea) were recorded. Richness and abundance of native, generalist, and above-ground nesting (cavities) species were higher than that of exotic, specialist, and below-ground (soil) nesting ones, respectively. Social bees were more abundant, while the richness of solitary species was higher than that of social bees. Cleptoparasitic species were represented by a high number of species, even though only a few individuals were captured. Our results suggest that the studied area is an important bee reservoir within the city.     

Odonata Diversity and Synanthropy in Urban Areas: A Case Study in Avellaneda City,Buenos Aires,Argentina

The increase of human population, especially in urban areas, correlates with an alarming destruction of green spaces. Therefore, understanding the mechanisms by which urbanization processes affect biodiversity is crucial in integrating the environment in a proper urban planning. The main urban center of Argentina is known as the Greater Buenos Aires (GBA), and it includes the autonomous city of Buenos Aires and 24 surrounding districts. Avellaneda, one of the districts of the GBA, is an important urban and industrial center with green areas and low level of urbanization on the coastal area of the Río de la Plata. This paper provides the first Odonata inventory for Avellaneda, determines the species’ level of synanthropy with the Nuorteva index, and assess the Odonata species replacement along a latitudinal gradient on the occidental margin of the Río de la Plata.