RESUMEN

Climatic fluctuations during the Last Glacial Maximum (LGM) exerted a profound influence on biodiversity patterns, but their impact on bryophytes, the second most diverse group of land plants, has been poorly documented. Approximate Bayesian computations based on coalescent simulations showed that the post-glacial assembly of European bryophytes involves a complex history from multiple sources. The contribution of allochthonous migrants was 95-100% of expanding populations in about half of the 15 investigated species, which is consistent with the globally balanced genetic diversities and extremely low divergence observed among biogeographical regions. Such a substantial contribution of allochthonous migrants in the post-glacial assembly of Europe is unparalleled in other plants and animals. The limited role of northern micro-refugia, which was unexpected based on bryophyte life-history traits, and of southern refugia, is consistent with recent palaeontological evidence that LGM climates in Eurasia were much colder and drier than what palaeoclimatic models predict.

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RESUMEN

Deep geothermal energy is a local energy resource that is based on the heat generated by the Earth. As the heat is continuously regenerated, geothermal exploitation can be considered as a renewable and, depending on the techniques used, a sustainable energy production system. In September 2015, the Flemish Institute for Technological Research (VITO) started drilling an exploration well targeting a hot water reservoir at a depth of about 3km on the Balmatt site near Mol. Geothermal hot water contains naturally occurring gases, chemicals and radionuclides at variable concentrations. The actual concentrations and potentially related hazards strongly depend on local geological and hydrogeological conditions. This paper summarizes the radiological characterization of several rock samples obtained from different depths during the drilling, the formation water, the salt and the sediment fraction. The results of our analyses show low values for the activity concentration for uranium and thorium in the formation water and in the precipitate/sediment fraction. Also, the activity concentrations of 210Pb and 210Po are low in these samples and the activity concentration of 226Ra is dominant. From the analysis of the rock samples, it was found that the layer above the reservoir has a higher uranium and thorium concentration than the layer of the reservoir, which on the other hand contains more radium than the layer above it.

RESUMEN

Unraveling the macroevolutionary history of bryophytes, which arose soon after the origin of land plants but exhibit substantially lower species richness than the more recently derived angiosperms, has been challenged by the scarce fossil record. Here we demonstrate that overall estimates of net species diversification are approximately half those reported in ferns and ∼30% those described for angiosperms. Nevertheless, statistical rate analyses on time-calibrated large-scale phylogenies reveal that mosses and liverworts underwent bursts of diversification since the mid-Mesozoic. The diversification rates further increase in specific lineages towards the Cenozoic to reach, in the most recently derived lineages, values that are comparable to those reported in angiosperms. This suggests that low diversification rates do not fully account for current patterns of bryophyte species richness, and we hypothesize that, as in gymnosperms, the low extant bryophyte species richness also results from massive extinctions.

RESUMEN

Formica polyctena antidiuretic factor (FopADF) was purified from a 15% trifluoroacetic acid (TFA) extract of the abdomens of 150,000 worker ants. After solid phase extraction of the crude extract and reversed-phase HPLC on two C(18) columns, an antidiuretic factor was isolated. Tested at a concentration of 1.0 ant-equivalents/µl (ant-eq/µl), the factor reversibly inhibited fluid secretion of isolated Malpighian tubules to 29+/-5% (mean+/-SE, n=24) of the control value. The same concentration of FopADF reversibly depolarized both the basolateral membrane potential (V(bl)), from -21+/-2 mV to -3+/-1 mV (n=5), and the apical membrane potential (V(ap)), from -65+/-5 mV to -20+/-5 mV (n=5). Similar effects on fluid secretion and V(ap) were caused by a TFA extract of the haemolymph of ants with non-secreting tubules. Unfortunately, further purification of FopADF on a C(4) column led to a loss of activity in the fluid secretion assay. This is the first time an endogenous antidiuretic factor acting directly on Malpighian tubules has been partially purified and shown to depolarize the tubule cell membranes.

RESUMEN

A peptide was purified from a 10% trifluoroacetic acid (TFA) head/thorax extract of 300,000 ants with high performance liquid chromatography (HPLC). Fluid secretion assay of single isolated Malpighian tubules was used as a bioassay. The purity of F. polyctena diuretic peptide (FopDP) after a two step HPLC protocol was confirmed by means of mass spectrometry and revealed a molecular mass of 7514 daltons. Due to lack of material, no enzymatic digestion could be performed and the sequence of only the first 25 amino acids could be determined: VPKYENCVSEVLPAGDRQRCVKVTC. A computer search of sequence data banks did not reveal any significant similarity between FopDP and other known insect diuretic peptides.FopDP had no effect on the basolateral membrane potential and depolarised the apical membrane potential of the Malpighian tubule cells. This effect as well as the stimulatory effect on the primary urine formation in the Malpighian tubule of the ant, could be mimicked with A23187, a calcium ionophore, and by thapsigargin, an inhibitor of the endoplasmic reticulum calcium ATPase. FopDP did not stimulate the cAMP content. The results suggest that FopDP uses an increase of intracellular calcium as cellular transduction mechanism.