The combined effects of climate change and river fragmentation on the distribution of Andean Amazon fishes

Upstream range shifts of freshwater fishes have been documented in recent years due to ongoing climate change. River fragmentation by dams, presenting physical barriers, can limit the climatically induced spatial redistribution of fishes. Andean freshwater ecosystems in the Neotropical region are expected to be highly affected by these future disturbances. However, proper evaluations are still missing. Combining species distribution models and functional traits of Andean Amazon fishes, coupled with dam locations and climatic projections (2070s), we (a) evaluated the potential impacts of future climate on species ranges, (b) investigated the combined impact of river fragmentation and climate change and (c) tested the relationships between these impacts and species functional traits. Results show that climate change will induce range contraction for most of the Andean Amazon fish species, particularly those inhabiting highlands. Dams are not predicted to greatly limit future range shifts for most species (i.e., the Barrier effect). However, some of these barriers should prevent upstream shifts for a considerable number of species, reducing future potential diversity in some basins. River fragmentation is predicted to act jointly with climate change in promoting a considerable decrease in the probability of species to persist in the long‐term because of splitting species ranges in smaller fragments (i.e., the Isolation effect). Benthic and fast‐flowing water adapted species with hydrodynamic bodies are significantly associated with severe range contractions from climate change.     

On the properties of calcium-induced permeability transition in neonatal heart mitochondria

Permeability transition was examined in heart mitochondria isolated from neonate rats. We found that these mitochondria were more susceptible to Ca(2+)-induced membrane leakiness than mitochondria from adult rats. In K(+) containing medium, at 25?°C, mitochondria were unable to accumulate Ca(2+). Conversely, in Na(+) containing medium, mitochondria accumulated effectively Ca(2+). At 15?°C mitochondria accumulated Ca(2+) regardless of the presence of K(+). Kinetics of Ca(2+) accumulation showed a similar Vmax as that of adult mitochondria. Lipid milieu of inner membrane contained more unsaturated fatty acids than adult mitochondria. Aconitase inhibition and high thiobarbituric acid-reactive substances (TBARS) indicate that oxidative stress caused mitochondrial damage. In addition, proteomics analysis showed that there is a considerable diminution of succinate dehydrogenase C and subunit 4 of cytochrome oxidase in neonate mitochondria. Our proposal is that dysfunction of the respiratory chain makes neonate mitochondria more susceptible to damage by oxidative stress.     

Nitrogen and potassium variation on contaminant removal for a vertical subsurface flow lab scale constructed wetland

Lab scale constructed wetlands were used to evaluate organic load removal efficiency. Bioreactors were fed with synthetic wastewater (SW) with varying concentrations of nitrogen and potassium. Reactors were planted with species Phragmites australis. Fed theoretic COD was adjusted to 240.0 mg-O₂ L⁻¹, nitrogen levels were 10 and 40 mg-N L⁻¹ (ammonium sulfate), potassium levels were 5 and 31 mg-K L⁻¹ (potassium monobasic phosphate). The higher biomass yield, for 0.5 and 0.775 N:K ratios, was related with higher organic load removal. The ratio N:K showed significant differences for organic load abatement, when 1:0.5 and 1:0.775 N:K ratios were applied, 96.8% efficiency was obtained, whereas N:K ratio of 1:0.125 had efficiency of 92.1% and N:K ratio of 1:3.1 showed an efficiency of 90.5%. For planted bioreactor E_H decreased in 162.7 mV from sample port to 5 cm down to 35 cm depth, while for the bioreactor without plant showed an E_H decrement of only 17.7 mV.     

Monitoring respiration and biological stability during sludge composting with a modified dynamic respirometer

A static electrolytic respirometer was adapted to work under dynamic conditions using an internal airflow recirculation system that passed air through sludge/straw solid mixtures. Airflow reduced oxygen transfer limitations and increased the maximum respiration rate and k_La values, indicating that the observed value may have been close to the actual biodegradation rate. Airflow caused sludge drying, so the sample moisture was controlled by air humidification. To apply the optimised respirometric technique, a pilotscale composting process was developed. Some commonly used respiration indices (RI₂₄, AT₄) were used to measure the final compost stability. RI₂₄ indices without airflow were underestimated during the thermophilic composting stage. Once the easily biodegradable carbon was consumed, the static and dynamic RI₂₄ indices were nearly identical. Because of the dynamic procedure, the respiration rate was likely controlled by the biochemical reaction and not by the mass transfer. The respiration indices indicated that the final compost was unstable.     

Identification of regions critically affecting kinetics and allosteric regulation of the Escherichia coli ADP-glucose pyrophosphorylase by modeling and pentapeptide-scanning mutagenesis

ADP-glucose pyrophosphorylase (ADP-Glc PPase) is the enzyme responsible for the regulation of bacterial glycogen synthesis. To perform a structure-function relationship study of the Escherichia coli ADP-Glc PPase enzyme, we studied the effects of pentapeptide insertions at different positions in the enzyme and analyzed the results with a homology model. We randomly inserted 15 bp in a plasmid with the ADP-Glc PPase gene. We obtained 140 modified plasmids with single insertions of which 21 were in the coding region of the enzyme. Fourteen of them generated insertions of five amino acids, whereas the other seven created a stop codon and produced truncations. Correlation of ADP-Glc PPase activity to these modifications validated the enzyme model. Six of the insertions and one truncation produced enzymes with sufficient activity for the E. coli cells to synthesize glycogen and stain in the presence of iodine vapor. These were in regions away from the substrate site, whereas the mutants that did not stain had alterations in critical areas of the protein. The enzyme with a pentapeptide insertion between Leu(102) and Pro(103) was catalytically competent but insensitive to activation. We postulate this region as critical for the allosteric regulation of the enzyme, participating in the communication between the catalytic and regulatory domains.     

Nucellar beak structure and pollen tube growth in Cucurbitaceae

The nucellar beak is a proboscis-like outgrowth of the nucellus at the micropylar end, being the obligatory path for the pollen tube entering the ovule. Among the few angiosperm families with nucellar beak, Cucurbitaceae is remarkable because the pollen tube may develop at least two types of growth within the nucellar beak: tubular and ampulliform. Wondering about the possibility that Cucurbitaceae ovules may express some histological variation that could be related to pollen tube growth within the nucellar beak, we performed a compared anatomical and histochemical study of the nucellar beak and the pollen tube growth of ten species of Cucurbitaceae. Results show that Cucurbitaceae ovules are diverse in size and proportions (of integuments, nucellar body, and nucellar beak), and they have at least four types of nucellar beak histology: pectic-tracked, secretory-like, amylaceous, and mixed. Amylaceous and mixed nucellar beaks are related to the ampulliform growth of the pollen tube, which could have appeared independently in most derived tribes of Cucurbitaceae, although information about nucellar beak structure in the basal tribes is still needed. In addition, the understanding of the relation between amylaceous nucellar beaks and the ampulliform growth of the pollen tube, whose function is still to be discovered, might open the possibility of a unique model of pollen tube-ovule co-evolution in angiosperms.     

Giant sex chromosomes retained within the Portuguese lineage of the field vole (<Emphasis Type="Italic">Microtus agrestis</Emphasis>)

The field vole (Microtus agrestis) is characterised by extremely large blocks of heterochromatin on both the X and Y chromosome. Some other Microtus also have blocks of heterochromatin on their sex chromosomes but not as extensive and always of independent origin from the heterochromatic expansion found in M. agrestis. Coupled with evidence of geographic variation in large heterochromatic blocks within other species (e.g. in the western hedgehog Erinaceus europaeus), it might be expected that field voles would show substantial variation in size and disposition of the sex chromosome heterochromatin. In fact, only minor variation has been described up to now. Those studies conducted previously were largely on field voles from central and northern Europe. Here, we describe the karyotype of field voles from Portugal, of interest because recent molecular studies have shown field voles from western Iberia to be a separate evolutionary unit that might be considered a cryptic species, distinct from populations further to the east. The two Portuguese field voles (one female, one male) that we examined also had essentially the same karyotype as seen in other field voles, including the giant sex chromosomes, but with small differences in the structure of the Y chromosome from that described previously. The finding that field voles throughout Europe show relatively little variation in their giant sex chromosomes is consistent with molecular data which suggest a recent origin for this complex of species/near-species.