Thallium Behavior in Soils Polluted by Pyrite Tailings (Aznalcóllar,Spain)

Thallium content and chemical speciation was studied at 91 sites contaminated by water and tailings spilled from the settling pond of a pyrite mine into the Agrio and Guadiamar rivers in Aznalcóllar (Spain). The contamination was highly heterogeneous, with 15% of the affected area seriously contaminated, 55% moderately contaminated and 30% uncontaminated. The total Tl content in the surface horizon increased with respect to the background level, more than 4-fold in the uppermost 10 cm of the soils, and clearly decreased with depth without contaminating either the subsoil or groundwater. Most of the Tl (approximately 75%) was in non-extractable forms, either as a component of the particles in the tailings or adsorbed to crystalline oxides. The remaining Tl was held on, or occluded in, amorphous or poorly crystallized oxides. In acidic soils, the adsorption of Tl was dominated by iron oxides (Feo) and, in neutral-alkaline soils, by aluminium oxides (Alo). A relatively high amount of the Tl adsorbed by amorphous oxides in the uppermost 10 cm of the soils was extracted with acetic acid, and was presumably bio-available (mean values approximately 15% of the Tlo). The EDTA is a strong extractant of inorganic forms of aluminium and, consequently, the quantity of Tl extracted by EDTA in neutral-alkaline soil (mean values more than 10% of the total Tl) could be higher than the truly bio-available fraction. Approximately 1% of the total Tl was extracted with calcium chloride, but only in the neutral-alkaline soil was the extraction significantly related to the cation-exchange capacity and, thus, adsorbed by the negative charges of the clay and organic matter. The Tl soluble in water (< 0.1%) declined with the pH in the neutral-alkaline soils, and was unrelated to any soil property in the acid soils. Thus, the behavior of Tl is determined by climatic conditions, soils properties and time.     

Quantity versus quality: Endemism and protected areas in the temperate forest of South America

Abstract Identification of biodiversity hotspots is essential to conservation strategies aimed at minimizing the possibility of losing half of the world's species in the next 50 years. The aims of the present study were: (i) to locate and designate zones of endemism in the temperate forest of South America; and (ii) to compare the distribution of these areas with the distribution of existing protected areas in this habitat type. Endemism areas were determined by using parsimonious analysis of endemism, which identified zones of endemism on the basis of sets of endemic species that were restricted to two or more study areas. We used distribution information for five unrelated taxa (ferns, trees, reptiles, birds and mammals) to provide more reliable results and patterns than would work with only a single taxon or related taxa. The northern part of this region has high endemism for all of the taxa considered in this study. We demonstrate that although the temperate forest of South America has more than 30% of its area under some type of protection, correlation between protected areas and the areas of endemism is remarkably low. In fact, less than 10% of protected areas are situated in areas that have the greatest value for conservation (i.e. high endemism). Under the current strategy, biodiversity within South America's temperate forest is in danger despite the large amount of protected area for this forest type.     

Chemical Composition of Viscin Mucilage from Three Mistletoe Species--A comparison

The viscin of mistletoes is a unique tissue which serves toprovide strong adherence of the seed of the parasite to thehost branch. The viscin mucilage of three species, Phoradendroncalifornicum and Arceuthobium americanum (Viscaceae) and Phthirusapyrifolia (Loranthaceae), was analysed. The major componentof the mucilage of Pho. californicum and A. americanum was polysaccharidic;of this, neutral sugars comprised the largest portion, but substantialamounts of uronic acids and proteins were also present. Xyloseand arabinose were the most abundant of the neutral sugars,and analysis showed glycine to be the most abundant amino acidas well as the presence of higher-than-average amounts of histidine.In contrast, in the mucilage of Pht. pyrifolia glucose was themost abundant neutral sugar and the protein content was substantiallyhigher. Based on the differences in composition observed amongthe different species the future use of viscin components astaxonomic markers is suggested. Viscin mucilage, mistletoes, Arceuthobium americanum, Phthirusa pyrifolia, Phoradendron californicum, g.l.c., amino acid analysis     

Influence of bacterial density and water temperature on the grazing activity of two freshwater ciliates

1. The influences of bacterial density and water temperature on the grazing activity of the ciliates Uronema sp. and Colpoda inflata were studied. The conditions assayed were two prey densities (10⁶ and 4 × 10⁷ bacteria ml^?1) and three water temperatures (10, 15 and 22 °C). 2. The response of the ciliates was measured from changes in protistan biovolumes and specific clearance rates. At high prey density, both ciliates showed lower biovolumes as water temperature increased, while at low prey density this tendency was minimized. 3. At the intermediate temperature of 15 °C both ciliates filtered ten times more body volume when bacteria were scarce; however, the ingested bacteria were fewer than at high prey density. At low prey density, a decrease from 15 to 10 °C evidenced different strategies of the two ciliates, which led to a similar ingestion of bacteria: C. inflata reduced its specific clearance rates and increased its biovolume, while Uronema sp. did not show changes. At high prey density, an increase from 15 to 22 °C caused lower biovolumes and a noticeable increase in specific clearance rates in both ciliates, indicating opportunist behaviour.     

Catechol Oxidase in Suspension Cultures of Apple Fruit--The Effects of Growth Regulators

Growth and catechol oxidase activity were followed in suspensioncultures of cells derived from apple fruit. In cultures whichrequired the addition of hormones, enzyme activity was affectedby 2, 4-D (2, 4-dichlorophenoxyacetic acid) and kinetin viatheir effect on growth. Exogenous hormones did not affect catecholoxidase activity of habituated cultures. Ethylene and PCIB (-4-chlorophenoxyisobutyricacid) rapidly depressed enzyme activity in all cell fractions,but only at concentrations which repressed growth. Ethioninecaused an immediate decrease in enzyme activity which precededthe repression of growth. Ethionine did not inhibit enzyme activityin vitro. Possible mechanisms of the action of ethionine arediscussed and the formation of a specific inhibitor is hypothesized.     

The role of historical factors and natural selection in the evolution of breeding systems of Oxalis alpina in the Sonoran desert ‘Sky Islands’

Pleistocene climatic oscillations are known to influence the patterns of genetic diversity and the distribution of traits that are the target of selection. Here, we combine phylogeographical and ecological niche modelling (ENM) approaches to explore the influence of historical factors (Pleistocene climatic shifts) and natural selection on the evolution of distyly (two floral morphs) from tristyly (three floral morphs) of Oxalis alpina in the Sky Islands of the Sonoran Desert. Molecular data and ENM indicate that historical factors have had a strong influence on the genetic structure and the geographical distribution of reproductive systems of O. alpina. Moreover, genetic results suggest the possibility that distylous populations do not represent a monophyletic group. We propose that the combined effects of natural selection and genetic drift have influenced the tristyly–distyly transition.     

Relationships between altitude,triatomine (Triatoma dimidiata) immune response and virulence of Trypanosoma cruzi,the causal agent of Chagas' disease

Little is known about how the virulence of a human pathogen varies in the environment it shares with its vector. This study focused on whether the virulence of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae), the causal agent of Chagas' disease, is related to altitude. Accordingly, Triatoma dimidiata (Hemiptera: Reduviidae) specimens were collected at three different altitudes (300, 700 and 1400 m a.s.l.) in Chiapas, Mexico. The parasite was then isolated to infect uninfected T. dimidiata from the same altitudes, as well as female CD‐1 mice. The response variables were phenoloxidase (PO) activity, a key insect immune response, parasitaemia in mice, and amastigote numbers in the heart, oesophagus, gastrocnemius and brain of the rodents. The highest levels of PO activity, parasitaemia and amastigotes were found for Tryp. cruzi isolates sourced from 700 m a.s.l., particularly in the mouse brain. A polymerase chain reaction‐based analysis indicated that all Tryp. cruzi isolates belonged to a Tryp. cruzi I lineage. Thus, Tryp. cruzi from 700 m a.s.l. may be more dangerous than sources at other altitudes. At this altitude, T. dimidiata is more common, apparently because the conditions are more beneficial to its development. Control strategies should focus activity at altitudes around 700 m a.s.l., at least in relation to the region of the present study sites.     

Sarcosaprophagous Diptera assemblages in natural habitats in central Spain: spatial and seasonal changes in composition

The composition and spatial distribution of sarcosaprophagous Diptera assemblages were studied using carrion‐baited traps along a bioclimatic gradient of natural habitats in central Spain throughout the different seasons during 1 year. Calliphoridae and Muscidae were the most abundant families, accounting for, respectively, 41.9% and 35.1% of all Diptera specimens collected. Other abundant families were Heleomyzidae (8.4%), Sarcophagidae (6.9%) and Piophilidae (5.1%). Fly assemblage compositions differed among bioclimatic levels, with Chrysomya albiceps (Wiedemann) (Diptera: Calliphoridae) being the dominant species in mesomediterranean habitats, Muscina levida (Harris) (Diptera: Muscidae) the dominant species in supramediterranean habitats, and Prochyliza nigrimana (Meigen) (Diptera: Piophilidae) the dominant species in oromediterranean habitats. Differences in assemblage composition were also found among seasons. Thermophobic species such as Calliphora vicina Robineau‐Desvoidy (Diptera: Calliphoridae) and some species of Heleomyzidae were well represented during autumn, winter and spring in the three bioclimatic levels sampled. By contrast, thermophilic species such as Ch. albiceps and Lucilia sericata (Meigen) (Diptera: Calliphoridae) and most Muscidae and Sarcophagidae species were more abundant during summer and in mesomediterranean habitats located at lower elevations. Knowledge of the preferences of some species for certain habitats may be of ecological and forensic value and may establish a starting point for further research.     

Ethanol production from two varieties of henequen (Agave fourcroydes Lem)

This work demonstrates the significant differences in ethanol production of two henequen (Agave fourcroydes Lem) varieties. Yaax ki, or green henequen, surpasses Sac ki, or white henequen, in weight, sugar accumulation capability and ethanol production. The study was carried out with the ‘piña’ (stem and basal part of the leaves that remain attached to it after harvesting the leaves) of 5‐ and 9‐year‐old plants, cultivated in two localities of Yucatán, México. At 5 years of age, Yaax ki piñas are 33% larger than those of Sac ki, and at 9 years this difference can increase to 59%. Juice from 5‐year‐old piñas of Yaax ki contains 15.6% more reducing sugars, whereas in the must it can exceed 67%. Values obtained in the 9‐year‐old plants indicate that the Yaax ki variety accumulates 30.6% more reducing sugars than the Sac ki, whereas in the must the difference is in favor of Yaax ki is 21.7%. To produce 1 L of ethanol at 40% concentration by volume from 5‐year‐old plants, 48 kg of Sac ki piñas and 29 kg of Yaax ki are required, whereas with the 9‐year‐old plants, only 23 and 19 kg are needed, respectively.     

Extraction and Preliminary Use for Diagnosis of Soluble Precipitating Antigen from Babesia bigemina*

Soluble antigen from bovine blood with a Babesia bigemina parasitemia of 5–6% formed 4 precipitin lines in gel diffusion tests with antiserum from infected cattle. Antigen was obtained from plasma and hemolysate by elution from DEAE cellulose columns and (NH₄)₂SO₄ precipitation as well as from washed parasite-erythrocyte stroma by sonication or freezethawing. About 5 ml of antigen suitable for diagnostic tests could be extracted from 200 ml of infected blood.