Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Rhinella schneideri (or Bufo paracnemis), popularly known in Brazil as cururu toad, is also found in other countries in South America. The cardiovascular effects of this poison are largely known and recently was shown that it is capable to affect the neuromuscular junction on avian and mice isolated preparation. In this work, we used transmission electron microscopy to investigate the ultrastructure of the motor nerve terminal and postsynaptic junctional folds of phrenic nerve-hemidiaphragm preparations incubated for either 5 or 60 min with the methanolic extract of R. schneideri (50 µg/mL). In addition, the status of the acetylcholine receptors (AChR) was examined by TRITC-α-bungarotoxin immunofluorescence location at the endplate membrane. The results show that 5 min of incubation with the gland secretion extract significantly decreased (32 %) the number of synaptic vesicles into the motor nerve terminal, but did not decrease the electron density on the top of the junctional folds where nicotinic receptors are concentrated; however, 60 min of incubation led to significant nerve terminal reloading in synaptic vesicles whereas the AChR immunoreactivity was not as marked as in control and after 5 min incubation. Muscle fibers were well-preserved but intramuscular motor axons were not.  The findings corroborated pharmacological data since the decrease in the number of synaptic vesicles (5 min) followed by recovery (60 min) is in accordance with the transient increase of MEPPs frequency meaning increased neurotransmitter release. These data support the predominant presynaptic mode of action of the R. schneideri, but do not exclude the possibility of a secondary postsynaptic action depending on the time the preparation is exposed to poison.

Abstract: Influence of cattle ranching on the community of aquatic macroinvertebrates in watersheds of central Andes, Colombia. In order to measure the impact of cattle ranching and riparian corridors on the composition and diversity of benthic macroinvertebrates in Andean watersheds, nine headwater streams were selected in the municipality of Villamaría (Caldas, Colombia), five of them with riparian corridors and four without protection. In july (2013) in each stream, macroinvertebrate samples were collected using D and Surber nets, and streams were characterized according to water quality, channel metrics and habitat quality score. In total 98 934 individuals were collected, distributed in nine classes, 17 orders, 56 families and 92 genera. Veneroidea was the most abundant order followed by Trichoptera, Diptera, Tubificida and Ephemeroptera. Coleoptera was the order with highest richness with 28 genera, followed by Diptera with 18, Trichoptera with 11, Ephemeroptera with 10 and Odonata with 8. Streams with riparian corridors were deeper, had higher proportion of coarse substrates and Habitat Quality Score and presented higher genus diversity than those unprotected (p<0.05). The genera Ferrisia, Eurygerris, Heleobia and Pisidium, total nitrogen, ammonia nitrogen and silt proportion on the streambed were correlated with unprotected streams, whilst the genus Rhagovelia, the subfamily Chironominae, the Habitat Quality Score and the proportion of coarse substrates were correlated with streams with riparian corridors. This information confirms that riparian corridors help reducing the negative impact generated by cattle ranching practices and improve the provision of environmental services, and therefore it is recommended to maintain the strip of riparian vegetation in streams that possess it and allow the establishment of this in streams devoid of forest on its slopes.Key words: Watersheds, riparian corridors, benthos, water quality.

Interspecific interactions among tropical mesocarnivorous species and other mammalian trophic guilds have been poorly studied, despite they have important implications in the survival, structure, demography, and distribution of these species. In this study we analyzed spatio-temporal interactions of three sympatric mesocarnivores that are located in the Northeastern limit of their geographic distribution in Mexico, with the objective of analyzing if these species coexist or compete in the axis of the temporal and spatial niche. With a sampling period from January 2015 to December 2016 and 26 camera-trapping stations (with in a set of two camera traps opposite to each other) and located along roads and animal trails, we determined the activity pattern and habitat use of L. wiedii (margay), L. pardalis (ocelote) y P. yagouaroundi (yaguarundi). All independent photographs of each species were grouped into three temporal categories (day, night and twilight) and six habitat categories; Oak Forest, Oak-Pine Forest, Cloud Forest, Pine-Oak Forest, Tropical Deciduous Forest and Medium Forest. Temporal and spatial overlap between species (i.e interactions) was obtained with the Czekanowski index and the Pianka index, respectively. These indices are symmetrical and take values from zero to one, where the results close to zero indicate that there is no overlap between species and values close to one indicate overlap. We obtained a total of 379 independent photographs, of which 239 corresponded to margay, 118 to ocelot and 22 to yaguarundi. Margay and ocelot were nocturnal, with 75 % of their records in this category showing a high temporal overlap (0.85); whereas yaguarundi was fully diurnal, suggesting it may be able to coexist with the other two species (margay and ocelot). Moreover, the yaguarundi used habitat similar to ocelot and margay (with high spatial overlap of 0.81 and 0.72, respectively), while the spatial overlap between the margay and ocelot was intermediate (0.53), since they used in most cases different habitat types. Our results suggest that there is no interspecific competition among these tropical mesocarnivorous species, probably due to antagonistic interactions among them on the temporal and spatial axis. These strategies may positively favor populations of mesocarnivores, which are characterized by having a high territorial behavior.

We present the results of conservation assessment of a rocky shore in the Central Pacific of Costa Rica (Playa Hermosa-Punta Mala National Wildlife Refuge) using the biological indicators proposed by the national environmental ministry. This study aims to analyze the influence of surveillance, between two sites, over the rocky shore habitat. The sampling was carried out during both the dry and rainy seasons in 2015. Our data shows that Nerita scabricosta -harvested in small-scale fisheries- presents a high number of colonies formed by few individuals. Moreover, the abundance varied between seasons, probably due to a storm surge. Macroalgae differed slightly among sites, where turf had higher percentage coverage in low surveillance areas, while brown algae had higher coverage in high surveillance areas. Mechanical damage (abrasion due to rocks overturning) associated with tourism and harvesting could be influencing the low surveillance area, explaining these differences. Macroalgae presented a seasonal change, probably related to the storm surge. The density of the Tetraclita stalactifera did not exhibit variations. The surveillance level and enforcement influenced some bioindicators of the rocky shore, and therefore could be used to assess the extractive pressure.

Arachnofauna studies from agroecosystems are crucial for implements spider as biological control agents. In this work we analyze the distribution of spider assemblages at three microhabitats (canopy, tree trunk and soil) in Citrus sinensis orchards (Rutaceae) in the Province of Corrientes, Argentina. Spiders were collected monthly using four sampling techniques: beating foliage, leaf litter sifting, pitfall traps and direct capture by hand. A total of 2 160 samples were examined and 7 194 spiders were collected (2 462 on the canopy, 983 on trunk and 3 749 on the floor) belonging to 34 families and 200 species/morphospecies of Araneomorphae. There were significant differences among microhabitats and months in the structure of the spider communities, according to analysis of similarity (ANOSIM). The diversity was highest on the canopy, followed by soil and tree trunk. Araneidae, Salticidae and Anyphaenidae were the most abundant taxa in the canopy; the dominant species were Jessica erythostoma and Cheiracanthium inclusum, a predator of the leaf herbivore Phyllocnistis citrella (Lepidoptera) a pest of Citrus spp. The most abundant families on the tree trunk were Tetragnathidae, Hersiliidae and Theridiidae, Iviraiva pachyura was a species specialist in such microhabitat; and Leucauge venusta was an opportunistic species, because their abundance increaseds markedly in anthropic environments that modified by man. The most abundant families on the floor were Lycosidae, Linyphiidae and Coriniidae. In this habitat, Lycosa erythrognatha and Pardosa plumipedata were dominant species. The Chao-Jaccard similarity index was highest between the canopy and trunk (J-C = 0.95), likewise ordination by nonmetric multidimensional scaling (NMDS) revealed strong differentiation between assemblages of soil spiders and canopy and trunk spiders. Also, on the soil the temporary replacement of species was greater and the seriation method was significant (z = 3.82, P = 0.00) therefore there was a succession of species during the year. The different species in each microhabitat probably avoided competition by using different hunting strategies and different ecological resources, in addition to specific patterns of temporal distribution. Our results suggest that anthropic environments, such as in Citrus orchards, tend to harbor populations of spiders able to adapt to those environments and interact in a balanced way in space and time.

The cellulolytic activity of fungi growing in the subtropical rainforest of Misiones (Argentina) represents a challenge in the technological development of the production of cellulosic bioethanol in the region using native sources. These fungi are promising to obtain sustainable enzyme cocktails using their enzymes. Cellulolytic ability of 22 white-rot fungi isolated from the subtropical rainforest of Misiones-Argentina in agar medium with two types of cellulosic substrates, carboxy-methylcellulose or crystalline cellulose, were comparatively analyzed, and the activity of two cellulolytic enzymes was evaluated in liquid medium. Although all isolates were able to grow and degrade both substrates in agar medium, and to produce total cellulase Filter paper (FPase) and endo-β-1,4-glucanase (EG) activities in broth, the isolate Irpex sp. LBM 034 showed the greatest enzymatic levels (FPase, 65.45 U L-1; EG, 221.21 U L-1). Therefore, the ITS sequence of this fungus was sequenced and analyzed through a phylogenetic analysis. These results indicate that the isolate LBM 034, corresponding to Irpex lacteus, has a promising cellulolytic ability and enzymes such as EG useful in sustainable saccharification of cellulosic materials in the region.

The coffee cultivation has displaced natural vegetation and its associated biological diversity. The present study describes the diversity of ground-dwelling ants on eight plantations where coffee is grown in the shade (SHD), eight plantations where coffee is grown under unshaded coffee (SUN) and four patches of forest (FOS) in a coffee-growing region of Colombia. The research was conducted in transects composed of 12 sampling stations, each of which employed active collection, pitfall traps and litter sifting. Nine habitat variables were analyzed to characterize each site, and these values were related to the diversity of ants and functional groups. A total of 92 morphospecies were collected. Myrmicinae was the subfamily with the highest representation. The sample coverage presented a deficit of less than 5 %. The rank abundance curves exhibited differences in the ant assemblages. The ant communities found in the forest exhibited greater diversity and a larger number of exclusive species than the communities found in locations of other land uses; the SHD and SUN communities were characterized by 80.3 % and 62.3 %, respectively, of the diversity found in the forest communities. The functional similarity index as adapted for guilds by Sørensen reveals a high degree of similarity in the structure of their ant communities, but less so in their composition. The shaded coffee plantations have a richer and more equitable ant fauna than the exposed coffee plantations, reinforcing the idea that shade cultivation favors the establishment of ant fauna and, consequently, ecological functionality. The shaded coffee plantations have a richer and more equitable ant fauna than the exposed coffee plantations, reinforcing the idea that shade cultivation favors the establishment of ant fauna and, consequently, ecological functionality.

This study integrated morphological characteristics and trophic ecology of Triportheus magdalenae in the El Guájaro reservoir, Atlántico, lower Magdalena River Basin, Colombia, based on the analysis of stomach contents and ecomorphological attributes. Five samplings were made between September 2014 and February 2016 considering each phase of the flood pulse. The fish were sampled using traditional fishing gear such as nets and trawls. The index of food importance (IAi %) was used to establish the dietary habits of the species, and the variation of the diet at interspecific level, and the vacuity coefficient (CV %) was also calculated. The Levins index standardized by Hurlbert (BA) was used to evaluate the amplitude between sizes, sex and hydrological phases. The oropharyngeal structures and the digestive tract were characterized, which together with morphological measurements, allowed and analyze 11 ecomorphological traits related to the use of habitat, such as position in the water column, and the exploitation of a particular trophic resource. The relationship between the ecomorphological traits and the diet of the species was analyzed by canonical correspondence analysis (CCA). We analyzed 89 individuals (34 - 124 mm SL). Triportheus magdalenae was classified as carnivore/zooplanktivore, and has a narrow trophic niche (BA = 0.12). Showed a high exploitation of zooplankton (95.9 % IAi), mostly Cladocera (Ceriodaphnia sp.) and Copepoda (Notodiaptomus sp. and Thermocyclops sp).  The youngest juveniles (34 - 190 mm SL) also consumed allochthonous insects (3.4 % IAi).The ecomorphological traits that contributed the most to this trophic specialization were the relative length of the gillrakers (LRBE) and the number of gillrakers (NBE), which varied significantly from the smaller to the larger ones, with an increase in both number as well as in length as individuals grow, which explains the strongly marked degree of specialization on zooplankton in adults, since they present a greater degree of efficiency in the process of filtering. The vacuity coefficient was high  (54 %), which could be associated with a decrease in the density of zooplankton populations, especially during the time of lower waters strongly influenced by the EL NIÑO event, however the observed diet (22 items food) corresponded to 80 % of the diet estimated (28 estimated food items). 

The Guarianthe skinneri orchid is included in NOM-059-ECOL-2010, Mexico standard as an endangered species. In order to study PGPR (promoting growth plant rhizobacteria) from this orchid, 10 roots were collected from different plants to isolate bacteria associated with the roots, which were analyzed by in vitro tests such as: production of AIA, nitrogen fixation, interaction with the mycorrhizal fungus Thanatephorus sp. strain RG26 and phosphate solubilization. We obtain 71 bacterial isolates, 10 strains of them were characterized by sequencing with the 16d rDNA marker identifying six bacteria: Sphingomonas sp. Sinorhizobium sp. Bacillus sp. Nocardia cerradoensis, Bacillus megaterium and Burkholderia phytofirmans. We observed that the bacterium Sinorhizobium sp. produced a greater amount of AIA (69.189 μg/ml) and Bacillus sp. performed greater acetylene reduction (10.251 nmol cultivo/96h). In the interactions of the bacteria and the fungus RG26, four categories were presented (extremely positive, positive, antagonism 50-50 and inhibition). In relation to the solubilization of phosphate, Burkholderia phytofirmans presented higher IS after 48 and 96 hr with an IS of 3.11 and 3.48, respectively. The results indicate that Bacillus sp. it could have the best characteristics to promote the development of the G. skinneri orchid by inoculating seeds and seedlings.