Landscape changes influence the reproductive behaviour of a key ‘capital breeder’ snake (Boa constrictor occidentalis) in the Gran Chaco region, Argentina     

Gabriela Cardozo  Margarita Chiaraviglio 《Biological conservation》2008,141(12):3050-3058

Many wild reptile species are threatened by habitat loss. However, the way in which changes in landscape patterns influence intraspecific ecological processes is not completely understood. Boa constrictor occidentalis is an endangered species and has a special conservation value since it is endemic of dry forests in the Gran Chaco region. Because the Gran Chaco is largely threatened due to habitat loss it is necessary to know how landscape changes influence this species. Therefore, we evaluated the effects of forest loss and landscape composition on the reproductive life-history parameters. Landscape changes were assessed by analyzing satellite imagery and reproductive parameters were determined by ultrasound images of the reproductive structures. The obtained results indicate that habitat loss may affect body condition, clutch size and testicular volume of the Argentine boa constrictor. We also found that the spatial pattern of vegetation influences the distribution of females and males in the landscape. Matting aggregations are scarce in shrublands. Therefore, our study shows that forest loss could enhance vulnerability to extirpation through constraints placed on reproduction. We encourage resource managers to evaluate sensitive reproductive life-history parameters as well as habitat deterioration to asses the conservation status of the populations of the Argentine boa constrictor. Since the Gran Chaco forest, a key habitat to the species’ reproduction, is largely threatened, strong conservation action is needed to halt and reverse forest loss in this region.  相似文献   

Posterotestes unelen gen. et sp. n. (Digenea: Apocreadiidae) from Percichthys trucha (Osteichthyes: Percichthyidae) in Patagonia, Argentina     

de Núñez MO  Brugni N  Flores VR 《Folia parasitologica》2003,50(3):211-214

Posterotestes gen. n. (Digenea: Apocreadiidae, Apocrcadiinae) is proposed for specimens with the following features: spiny body, posterior position of gonads, extension of vitelline follicles up to level of intestinal bifurcation and absent at post-testicular space, long oesophagus and extension of caeca up to anterior testis. Posterotestes unelen sp. n. is described from the intestine of the native fish, Percichthys trucha (Cuvier et Valenciennes) (Osteichthyes: Percichthyidae) from Patagonian Andean lakes.  相似文献   

The Ibizian hound presents a predominantly cellular immune response against natural Leishmania infection     

Solano-Gallego L  Llull J  Ramos G  Riera C  Arboix M  Alberola J  Ferrer L 《Veterinary parasitology》2000,90(1-2):37-45

Veterinarians working in the Balearic Islands (Mallorca), an endemic region of canine leishmaniosis, have reported very few cases of leishmaniosis in Ibizian hounds while concurrently observing that dogs of other breeds had a high incidence of clinical canine leishmaniosis. To further investigate this observation, two populations of dogs from the Balearic Islands were examined for the presence of Leishmania-specific cellular immunity using a delayed type hypersensitivity test (DTH) to leishmanin and for the presence of Leishmania-specific humoral immunity using an ELISA. Fifty-six asymptomatic dogs, 31 Ibizian hounds and 25 dogs belonging to other breeds were examined. Seventy-seven percent of the dogs demonstrated a specific immune response against Leishmania, either humoral or cellular. This finding suggests that the infection rate (77%) was higher than previously considered. For Ibizian hounds 81% were DTH positive while only 48% of the other dogs were DTH positive. A statistical association between Ibizian hounds and positive DTH response was found. A specific humoral response was found in 48% of Ibizian hounds and in 56% of the other dogs. No statistical association relative to the Leishmania-specific IgG1 and IgG2 levels were found between the two groups. The Ibizian hound has been reported to be more resistant to Leishmania infection and we found that the Ibizian hound mounts a significant cellular response to infection. Thus, the Ibizian hound may be an interesting canine model for the investigation of protective anti-Leishmania immune response.  相似文献   

The effect of the sampling scale on zooplankton community assessment and its implications for the conservation of temporary ponds in south‐west Spain     

Khalid Fahd  Margarita Florencio  Claudia Keller  Laura Serrano 《水产资源保护:海洋与淡水生态系统》2007,17(2):175-193

• 1. The zooplankton (rotifer and microcrustacean) assemblages of temporary ponds in the Doñana National Park (south‐west Spain) have been compared in two surveys of contrasting scales that resulted in the same number of samples: an extensive survey of 36 ponds sampled in May 1998 (or widespread survey) and a survey of nine ponds sampled four times over 2 years (or cumulative survey).
• 2. The total number of microcrustacean and rotifer taxa was larger in the cumulative survey (43 and 41 taxa, respectively) than in the widespread survey (39 and 34, respectively). Crustacean assemblages became less alike throughout the cumulative survey.
• 3. The presence of invertebrates (Coleoptera, Odonata, Heteroptera and crayfish) and aquatic vertebrates (fish and salamanders) was recorded as an estimate of potential predator impact on zooplankton. Several pond features (water depth, conductivity, pH, chlorophyll a concentration, distance to the nearest permanent pond and to the marsh) were also measured in both surveys.
• 4. A combination of these environmental factors was more strongly related to the similarity matrices derived from the zooplankton assemblages of the cumulative survey (Rho=0.7) than to those of the widespread survey (Rho<0.4). The distance of ponds to the marsh was an important factor in explaining this correlation as well as the strongest factor in the ordination of crustacean assemblages following a CCA.
• 5. Predation by exotic fish in long‐hydroperiod ponds where overflow drains to the nearby marsh (fish source) is the mechanism likely to explain the changes in crustacean composition recorded in the cumulative survey.
• 6. The cumulative survey was more suitable for the study of zooplankton diversity as it rendered a higher number of taxa and gave more insight into the mechanisms that explain taxon richness. Thus, conservation strategies in temporary habitats require a scale of observation that includes long temporal changes.

Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Essay of Different Extraction Procedures in Capelin Fish Meal for Biogenic Amine Determination by HPLC     

Claudia Ruiz-Capillas  Mehdi Triki  Cristina de las Heras  Margarita Tejada  Heiða Pálmadóttir  Rósa Porvaldsdóttir 《Journal Of Aquatic Food Product Technology》2013,22(5):443-453

This study assesses the effects of different extraction procedures of biogenic amines in capelin fish meal with different concentrations of trichloroacetic acid (TCA) for their determination by high performance liquid chromatography (HPLC). No significant differences were noted between the use of TCA at 7.5 and 10% for the extraction of biogenic amines in E1 and E3 extraction, except for tyramine. The extraction using 7.5% TCA in one step and centrifugation (E1) was a simple and rapid method. This extraction seems to be the most suitable for the extraction of amines in these kinds of samples, compared to the other methods tested. The biogenic amine that presented the highest levels in the fish meal studied was cadaverine (208–226 mg/kg), followed by putrescine and histamine (164–173 and 44–46 mg/kg, respectively). Biogenic amine levels were low when compared to the toxic levels observed in these kinds of products.  相似文献   

Cotyledon thermal behavior and pectic solubility as related to cooking quality in common beans     

Irma Bernal-Lugo  Carmen Parra  Margarita Portilla  Cecilia B. Peña-Valdivia  Ernesto Moreno 《Plant foods for human nutrition (Dordrecht, Netherlands)》1997,50(2):141-150

The characteristic of proteins, starch and pectic substances in cotyledons of two bean cultivars varying in cooking time were determined to investigate their possible contribution to bean cooking quality. Both cultivars showed the same enthalpies of starch gelatinization but different protein denaturation enthalpies. The proportion of hot water soluble pectins was higher in Michigan, the cultivar with the lower cooking time, than in Ojo de Cabra, the cultivar with the higher cooking time. These results were not due to differences in pectin methylation or in the ratio of monovalent to divalent cations in the tissue, suggesting that in fresh beans the β-elimination reaction is not the sole or predominant route of thermal pectin degradation. Overall, this study indicates that varietal differences in bean cooking quality may be reflections of the rate of pectin loss during soaking/heating and that the thermal properties of starch and protein fractions seem to have a minor contribution. Researchers involved in this study propose that in fresh beans, the thermal pectin loss results from a two step mechanism: pectin enzymic breakdown during the bean soaking followed by thermal solubilization rather than β-elimination during the bean heating.  相似文献   

Bacterial diversity and occurrence of ammonia-oxidizing bacteria in the Atacama Desert soil during a “desert bloom” event     

Julieta Orlando  Lorena Bravo  Margarita Carú 《Soil biology & biochemistry》2010,42(7):1183-6300

The Atacama Desert, located in northern Chile, is one of the driest deserts on the Earth. However, in some years, short and sporadic rainfall in the southern end of this desert has increased the soil moisture that produces ephemeral “desert bloom”. Our goal was to assess the composition of the bacterial community and determine variations in the ammonia-oxidizing bacteria guild diversity from soils collected during the course of the “desert bloom” event. The bacterial composition from this arid soil was determined by cloning and sequencing the 16S rRNA gene. A relatively high diversity of clones belonging to 14 bacterial groups was detected. The ammonia-oxidizers showed a significantly higher diversity of amoA gene clones after the “desert bloom” than during or at the beginning of this event. All sequences obtained were related to Nitrosospira genera and environmental clones. These results suggest that the diversity of ammonia-oxidizing bacteria in this arid soil can be affected by the occurrence of “desert bloom”.  相似文献   

Red List assessment of nine <Emphasis Type="Italic">Aegilops</Emphasis> species in Armenia     

Margarita Haruntyunyan  Mohammad Ehsan Dulloo  Naire Yeritsyan  Armen Danielyan 《Genetic Resources and Crop Evolution》2010,57(8):1177-1189

The aims of this study are to determine the geographical and ecological distribution of nine Aegilops species in Republic of Armenia and to make an assessment of their IUCN Red List status, using the IUCN Red list categories and criteria, in order to develop an in situ conservation strategy for wild relatives of wheat in Armenia. Ecogeographic surveys of nine Aegilops species were undertaken over 2 years in Armenia. They included a herbarium survey followed by extensive ground-truthing field surveys where targeted Aegilops species occur. The study showed that of the nine Aegilops species studied, four are threatened and of these, Ae. mutica and Ae. crassa are critically endangered. The latter species may even be extinct in Armenia. Ae. neglecta and A. biuncialis are endangered. Additional studies are required to assess the threat status of Ae. umbellulata. Ae. columnaris was assessed as near threatened, while the remaining species (Ae. triuncialis, Ae. cylindrica and Ae. tauschii) are of least concern. There has been a dramatic decline in the genetic resources of Aegilops species during recent years in Armenia as a result of adverse human impacts such as expansion of agriculture, urbanization and uncontrolled grazing. Several species, especially Ae. mutica and Ae. crassa, should be prioritized in conservation activities in Armenia. Efforts should be made to conserve genetic diversity of crop wild relative species both in situ and ex situ, bearing in mind that their germplasm carries potentially valuable information (traits) that can improve adaptability and productivity of cultivated wheat varieties.  相似文献   

The archaeology of Ushki Lake,Kamchatka, and the Pleistocene peopling of the Americas     

Goebel T  Waters MR  Dikova M 《Science (New York, N.Y.)》2003,301(5632):501-505

The Ushki Paleolithic sites of Kamchatka, Russia, have long been thought to contain information critical to the peopling of the Americas, especially the origins of Clovis. New radiocarbon dates indicate that human occupation of Ushki began only 13,000 calendar years ago-nearly 4000 years later than previously thought. Although biface industries were widespread across Beringia contemporaneous to the time of Clovis in western North America, these data suggest that late-glacial Siberians did not spread into Beringia until the end of the Pleistocene, perhaps too recently to have been ancestral to proposed pre-Clovis populations in the Americas.  相似文献   

Timing of precision agriculture technology adoption in US cotton production     

Pattarawan Watcharaanantapong  Roland K. Roberts  Dayton M. Lambert  James A. Larson  Margarita Velandia  Burton C. English  Roderick M. Rejesus  Chenggang Wang 《Precision Agriculture》2014,15(4):427-446

The timing of technology adoption is influenced by profitability and farmer ability to bear risk. Innovators are typically more risk tolerant than laggards. Understanding the factors influencing early adoption of precision agriculture (PA) technologies by cotton farmers is important for anticipating technology diffusion over time. The factors influencing the timing of grid soil sampling (GSS), yield monitoring (YMR) and remote sensing (RMS) adoption by cotton producers was evaluated using multivariate censored regression. Data for cotton farmers in 12 states were obtained from a survey conducted in 2009. The factors hypothesized to influence the timing of adoption included farm characteristics, operator characteristics, PA information sources, adoption of other PA technologies, and farm location. The results suggest that different factors influenced when cotton farmers adopted GSS, YMR and RMS after these technologies became commercially available. For example, land ownership was associated with the timing of GSS adoption, but not YMR or RMS adoption; farmer age was correlated with the timing of GSS and YMR adoption, but not RMS adoption; and obtaining PA information from consultants affected the timing of GSS and RMS adoption, but not YMR adoption. The only factors correlated with the early adoption of all three technologies were beliefs that PA would improve environmental quality and the adoption of at least one other PA technology. Thus, the potential for improved environmental quality appears to be a strong adoption motivator across PA technologies, as is the earlier adoption of other PA technologies. This research may be useful for farmers, researchers, Extension personnel, machinery manufacturers, PA information providers and agricultural retailers to anticipate the future adoption of new and emerging PA technologies.  相似文献