Baseline Levels of Potentially Toxic Elements in Pampas Soils

The soils of the Pampas are thought to be generally non-contaminated but there is growing evidence of trace element accumulation at some specific sites. The goal of this study was to measure the current levels of the main Potentially Toxic Elements (PTE) in the top horizon and in specific soil profiles so that we would establish the baseline concentrations of these elements. Eighty-eight top soils and three soil profiles were sampled. The samples were acid digested. Arsenic, boron, barium, cadmium, cobalt, chromium, copper, lead, manganese, mercury, molybdenum, nickel, silver, selenium and zinc were determined with inductively coupled argon plasma emission spectrometry (ICPES).

All of the values found are within the normal range for uncontaminated soils as reported from several continents. Elements with high environmental risk potential are lower than the admissible range of the European Union and some of them are orders of magnitude lower than those of the United States Environmental Protection Agency (US-EPA) 501 levels. Potentially Toxic Elements contents increased with depth or showed a maximum concentration at the B2 horizon. This is related to the parent material and the pedogenetic processes but not to recent contamination. Soil profiles showed higher concentrations of PTE in clayey horizons. However, these relationships did not appear in top soil samples in any soil Great Group studied. The shown data establishes a baseline for PTE concentrations for Pampas soils.     

Isolation and characterization of two different 5S rDNA in Anguilla anguilla and in Anguilla rostrata: possible markers of evolutionary divergence

We cloned and sequenced the HaeIII 350‐bp 5S ribosomal DNA (rDNA) band of Anguilla rostrata and designed specific primers from this sequence. Polymerase chain reaction performed with these primers is able to distinguish DNA samples obtained from European (Anguilla anguilla) and American (Anguilla rostrata) eels. Two amplicons of 1200 bp and 600 bp were obtained, respectively, from A. rostrata and A. anguilla, and the whole 5S rDNA repeated unit from these eels was cloned and sequenced. Southern blot experiments, using four different restriction enzymes and the 5S nontranscribed spacers regions as probe, are able to point out specific diversity in these eels.     

The Role of Acidocalcisomes in Parasitic Protists1

ABSTRACT. Acidocalcisomes are acidic organelles with a high concentration of phosphorus present as pyrophosphate (PP_i) and polyphosphate (poly P) complexed with calcium and other cations. The acidocalcisome membrane contains a number of pumps (Ca²⁺‐ATPase, V‐H⁺‐ATPase, H⁺‐PPase), exchangers (Na⁺/H⁺, Ca²⁺/H⁺), and channels (aquaporins), while its matrix contains enzymes related to PP_i and poly P metabolism. Acidocalcisomes have been observed in pathogenic, as well as non‐pathogenic prokaryotes and eukaryotes, e.g. Chlamydomonas reinhardtii, and Dictyostelium discoideum. Some of the potential functions of the acidocalcisome are the storage of cations and phosphorus, the participation of phosphorus in PP_i and poly P metabolism, calcium homeostasis, maintenance of intracellular pH homeostasis, and osmoregulation. In addition, acidocalcisomes resemble lysosome‐related organelles (LRO) from mammalian cells in many of their properties. For example, we found that platelet dense granules, which are LROs, are very similar to acidocalcisomes. They share a similar size, acidic properties, and both contain PP_i, poly P, and calcium. Recent work that indicates that they also share the system for targeting of their membrane proteins through adaptor protein 3 reinforces this concept. The fact that acidocalcisomes interact with other organelles in parasitic protists, e.g. the contractile vacuole in Trypanosoma cruzi, and other vacuoles observed in Toxoplasma gondii, suggests that these cellular compartments may be associated with the endosomal/lysosomal pathway.     

Influence of physical and chemical factors during foraging and culture of the symbiont fungus in Atta sexdens rubropilosa （Hymenoptera： Formicidae）

The aim of this paper is to investigate the influence of physical and chemical factors on transport and use of substrate for Atta sexdens rubropilosa workers. Three types of rectangular fragments were used to study the physical influence factors： filter paper with paraffin, filter paper without paraffin and polyester film. To study the chemical factors, some fragments were impregnated with organic extract of orange albedo, others were soaked with soybean oil and for the remaining ones nothing was applied. The fonowing parameters were evaluated： （i） attractiveness of substrate for transport and number of loading workers per treatment; （ii） foraged material incorporation; （iii） rejection by numbers of fragments deposited in the garbage or beside the fungus garden. All the polyester film fragments carried out to the fungus garden were subsequently rejected. We verified that chemical factors of the substrate were more quickly detected by the workers, whereas physical factors were used as a criterion in the decision-making to reject or accept the substrate collected.     

Out of the Neotropics: newly discovered relictual species sheds light on the biogeographical history of spider ants (Leptomyrmex,Dolichoderinae, Formicidae)

Spider ants of the genus Leptomyrmex Mayr (Hymenoptera: Formicidae: Dolichoderinae) are conspicuous species of Australasian rainforests, with putative fossil relatives in the Neotropics and Europe. There is longstanding debate over the biogeographical history of the genus, with the Palaearctic and Neotropical regions proposed as alternate centres of origin. We propose a resolution of this debate with the recent discovery and analysis of an extant species from central Brazil, L. relictus sp.n. , which we describe from workers, males and brood. We sequence ten nuclear genes in the new species and in several Australian Leptomyrmex species, and append these data to a 54‐taxon, 10‐gene data matrix previously generated for the subfamily Dolichoderinae. We conduct phylogenetic and divergence dating analyses, and re‐evaluate the fossil record of the group. We recover Leptomyrmex relictus sp.n. as a member of the Leptomyrmex clade with high support. It is sister to the Australasian species, and the genus Leptomyrmex is, in turn, sister to a pair of Neotropical genera, Forelius and Dorymyrmex. We infer a Neotropical origin for the genus and estimate a mid‐Eocene (46 Ma, 95% CI 56 to 36 Ma) origin for the crown genus and an Oligocene origin for the Australasian clade (29 Ma, 95% CI 40 to 19 Ma). We confirm placement of the Dominican amber species ?L. neotropicus Baroni Urbani in the genus but reject a close relationship with the Palaearctic fossil taxa ?Leptomyrmula Emery and ?Usomyrma Dlussky, Radchenko & Dubovikoff, considering them incertae sedis in the subfamily (Dolichoderinae). In contrast to the mesophilic preferences of the Australasian species of Leptomyrmex, the new Brazilian species inhabits cerrado (dry savannah). Our results support a Neotropical origin for spider ants with dispersal to Australia. Rafting on west‐bound currents and/or a historical diversity imbalance between Australia and South America are proposed as alternate hypotheses to explain a pattern of biased E–W mid‐Tertiary dispersal for ants with austral distributions. This pattern is suggested by our results in conjunction with observations of other ant clades. Overall, our findings highlight the value of integrated taxonomy, critical interpretation of morphology, and a comparative phylogenetic framework when conducting palaeontological and biogeographical studies of insect species. This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:6E9E6617‐6E53‐40B8‐82C7‐67F89A83C553 .     

Long-term dynamics of a freshwater sponge population

1. Quantitative field data were collected from a Sardinian population of the sponge Ephydutia fluvtatilis from 1987 to 1993 in order to study its life style. 2. Growth of sponges was high during the annual cycle, and showed few changes in 6 years. Gemmulation was very rapid and highly efficient. Life spans of many specimens extended up to 5 years. 3. The population was destroyed by one flood during our study period. The persistence of gemmules on substrata suggested that dispersal was low in our study population. Recolonization started 7 months after the flood and re-established a new population, different from the previous one in terms of spatial structure and specimen size.     

Input of organochlorine compounds by snow to European high mountain lakes

1.  Persistent organic pollutants (POPs) can be trapped by and accumulate in cold regions. To understand POP accumulation in temperate high mountain lakes, we collected samples of snow from the catchments of several high mountain lakes in Europe.
2.  Organochlorine compounds (OCs) are regularly found in snow collected in European high mountain sites. Polychlorobiphenyls (PCBs) were found in all samples examined. Hexachlorocyclohexanes (HCHs) are also common whereas DDTs and hexachlorobenzene were found less frequently.
3.  Comparison of the concentrations of these pollutants in snow with OC levels in the waters of these lakes or atmospheric deposition during cold periods shows that the snowpack constitutes a significant seasonal PCB reservoir in all catchments and that snow trapping is a major mechanism for the incorporation of HCHs in the lakes situated in the coldest sites, e.g. Gossenköllesee in the Alps.
4.  Correlation of the concentrations of the PCB congeners in snow versus mean annual winter temperature shows higher accumulation at lower temperatures. The less volatile PCBs exhibit higher temperature dependences than the more volatile congeners. This trend differs from altitudinal dependences observed in other sites such as Canada and may be related to the specific range of winter temperature in each area of study.