Influence of land use on stream ecosystem function in a Mediterranean catchment

1. Due to the hierarchical organization of stream networks, land use changes occurring at larger spatial scales (i.e. the catchment) can affect physical, chemical and biological characteristics at lower spatial scales, ultimately altering stream structure and function. Anthropogenic effects on streams have primarily been documented using structural metrics such as water chemistry, channel alteration and algal biomass. Functional parameters, including metrics of nutrient retention and metabolism, are now being widely used as indicators of stream condition. 2. Within this hierarchical context, we used a multivariate approach to examine how structural and functional (i.e. nutrient retention and metabolism) attributes of streams are related to catchment variables, including land use. The study was done in 13 streams located within a single Mediterranean catchment, but draining sub‐catchments with contrasting land use. 3. At the catchment scale, results showed two contrasting land use gradients: (i) from forested‐ to urban‐dominated catchments and (ii) from low to moderate agricultural‐dominated catchments. Variation in structural and functional parameters was strongly related to these land use gradients. Specifically, NH₄⁺ demand (measured as the uptake velocity, V_f) decreased along the gradient from forested‐ to urban‐dominated catchments primarily in response to increases in stream nutrient concentrations [NH₄⁺, dissolved organic nitrogen (DON) and carbon (DOC)]. Both primary production and respiration increased along the gradient of agricultural development in response to increases in algal biomass (chlorophyll a). Soluble reactive phosphorus demand was not related to any of the land use gradients. 4. Our results illustrate the connections among factors operating at different spatial scales (i.e. from catchments to streams) and their distinct influence on stream ecosystem function. Managers should take into consideration these connections when designing stream management and restoration plans. Because ecologically successful stream management and restoration is expected to restore function as well as structure to streams, the use of appropriate measures of functional processes is required. Nutrient retention and metabolism parameters are good candidates to fill this gap.     

Time-resolved fluoroimmunoassay of potato virus M with monoclonal antibodies

Mouse monoclonal antibodies (MAbs) specific for potato virus M (PVM) were prepared and the properties of three of them were studied. MAb M4C1 is IgG2b, it binds with high affinity to PVM coat protein, to purified virus preparations and recognises PVM in infected potato leaves and tubers. MAb M6D5 is IgG2a and also reacts with PVM coat protein, purified PVM and with PVM in potato leaf and tuber extracts. In double-antibody sandwich ELISA (DAS ELISA) MAbs M4C1 and M6D5 reacted with all 17 PVM isolates tested. MAb M7 is IgG2b and recognises PVM only in indirect dot ELISA on nitrocellulose filters and viral coat protein on Western blots. MAbs against PVM were used as capture antibodies and europium-labelled MAbs as conjugates in time-resolved fluoroimmunoassay (EuTRFIA). The standard EuTRFIA curve of PVM detection is approximately linear over a range of PVM concentrations from 0.5 ng/ml to 1000 ng/ml. The lowest PVM concentration detectable in EuTRFIA was 0.5 ng/ml and correspondingly 6 ng/ml in DAS ELISA. The use of the europium chelate label allows PVM detection in potato leaf and tuber sap at dilutions greater than 10^--⁴ with very low background fluorescence. EuTRFIA with MAbs, with either one or two incubations is about 10–20 times more sensitive for PVM detection than is DAS ELISA. PVM and PVX, mixed with healthy potato tuber sap, were simultaneously tested in a single sample at concentrations lower than 10 ng/ml by double-label TRFIA using europium-labelled MAbs to PVM and samarium-labelled MAbs to PVX.     

Lipophosphoglycan Is Present in Distinctly Different Form in Different Entamoeba histolytica Strains and Absent in Entamoeba moshkovskii and Entamoeba invadens1

ABSTRACT. Lipophosphoglycan has recently been demonstrated on the cell surface of Entamoeba histolytica strain HM-1:IMSS. A monoclonal antibody against this molecule had failed to react with some other strains of E. histolytica, including the strain Rahman. To determine if a structurally distinct lipophosphoglycan existed in Rahman, [³H]galactose-labeled glycoconjugates were electrophoresed through sodium dodecyl sulfate polyacrylamide gel electrophoresis. The electrophoretic pattern in Rahman was very different compared to that obtained with strains HM-1:IMSS and 200:NIH. A number of experiments including sensitivity to mild acid, nitrous acid and phosphoinositol-specific phospholipase C suggest that the Rahman glycoconjugate is indeed a lipophosphogylcan-like molecule but distinctly different from that of HM-1:IMSS. Mild acid-treated glycoconjugates from Rahman and HM-1:IMSS revealed the presence of neutral trisaccharides and monosaccharides in Rahman but not in HM-1:IMSS. Human immune sera from amoebiasis patients and a polyclonal antibody against HM-1:IMSS liphophosphoglycan both recognized Rahman glycoconjugate. Thus, while lipophosphoglycan molecules from the two strains share common epitopes, they are clearly distinct from each other. Molecules bearing resemblance to lipophosphoglycan could not be detected in other Entamoeba species, namely Entamoeba invadens and Entamoeba moshkovskii.     

Acclimation is beneficial at extreme test temperatures in the Danube crested newt, Triturus dobrogicus (Caudata, Salamandridae)

Despite many studies demonstrating the effect of acclimation on behavioural or physiological traits, considerable debate still exists about the evolutionary significance of this phenomenon. One of the unresolved issues is whether acclimation to warmer temperature is beneficial at treatment or at more extreme test temperatures. To answer this question, we assessed the effect of thermal acclimation on preferred body temperatures ( T _ps), maximum swimming and running speed, and critical thermal maximum ( CT _max) in the Danube crested newt ( Triturus dobrogicus ). Adult newts were kept at 15 °C (control) and 25 °C (treatment) for 8 weeks prior to measurements. We measured T _ps in an aquatic thermal gradient over 24 h, maximum speeds in a linear racetrack at six temperatures (5–33 °C), and CT _max in a continuously heated water bath. T _ps were higher in newts kept at 15 °C than in those kept at 25 °C. The maximum swimming speed did not acclimate. The maximum running speed at 30–33 °C was substantially higher in newts kept at 25 °C than in those kept at 15 °C. CT _max increased with the treatment temperature. Hence, we conclude that the acclimation response to warm temperature is beneficial not at treatment but at more extreme temperatures in newts.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 90 , 627–636.     

Micromammal biostratigraphy of the Upper Miocene to lowest Pleistocene continental deposits of the Guadix basin,southern Spain

Minwer‐Barakat, R., García‐Alix, A., Suárez, E.M., Freudenthal, M. & Viseras, C. 2012 xx xx: Micromammal biostratigraphy of the Upper Miocene to lowest Pleistocene continental deposits of the Guadix basin, southern Spain. Lethaia, Vol. 45, pp. 594–614. Recent study of the small mammals (rodents and insectivores) from several fossil‐bearing sites situated in the central sector of the Guadix Basin (Southern Spain) has notably increased the knowledge of the mammal assemblages that existed in Southern Iberia from the latest Miocene to the earliest Pleistocene. On the basis of this new information, we propose a biozonation for the continental deposits of the Guadix Basin, which consists of six biozones ranging in age from the late Turolian (MN13) to the early Villanyian (MN17). These biozones, defined according to the rules of the International Stratigraphical Guide, include not only the mentioned recently discovered fossil sites, but also other, previously known, localities of the basin. Finally, we integrate the described biozones in the Neogene Mammal units and the European Land Mammal Ages, correlate them with several classical mammal sites from other Iberian basins and the rest of Europe, and establish an approximate numerical age for the lower and upper limits of each biozone. □Biostratigraphy, Guadix Basin, rodents, insectivores, Upper Miocene, Pliocene, Pleistocene.     

Enhancement of root hydraulic conductivity by methyl jasmonate and the role of calcium and abscisic acid in this process

The role of jasmonic acid in the induction of stomatal closure is well known. However, its role in regulating root hydraulic conductivity (L) has not yet been explored. The objectives of the present research were to evaluate how JA regulates L and how calcium and abscisic acid (ABA) could be involved in such regulation. We found that exogenous methyl jasmonate (MeJA) increased L of Phaseolus vulgaris, Solanum lycopersicum and Arabidopsis thaliana roots. Tomato plants defective in JA biosynthesis had lower values of L than wild‐type plants, and that L was restored by addition of MeJA. The increase of L by MeJA was accompanied by an increase of the phosphorylation state of the aquaporin PIP2. We observed that MeJA addition increased the concentration of cytosolic calcium and that calcium channel blockers inhibited the rise of L caused by MeJA. Treatment with fluoridone, an inhibitor of ABA biosynthesis, partially inhibited the increase of L caused by MeJA, and tomato plants defective in ABA biosynthesis increased their L after application of MeJA. It is concluded that JA enhances L and that this enhancement is linked to calcium and ABA dependent and independent signalling pathways.