Escape performance in the sub-Antarctic notothenioid fish <i>Eleginops maclovinus</i>

Fast-start performance associated with escape behaviour was investigated in the sub-Antarctic notothenioid Eleginops maclovinus from the Beagle Channel, Tierra del Fuego, Argentina (mean winter water temperature 4degreesC, mean summer water temperature 10degreesC). Fish acclimated to 8.5degreesC for 2 months were filmed at 2, 4, 6, 8 and 10degreesC. Escape responses were temperature dependent over the range of temperatures tested. Maximum length-specific velocity ((V) over cap (max)), maximum length-specific acceleration ((A) over cap (max)) and inertial power output (P-iner) increased significantly with temperature. Q(10) values for (V) over cap (max), (A) over cap (max) and P-iner were 1.90, 3.27 and 8.90, respectively. Non-dimensional curvature of the spine ((c) over cap) also varied significantly with temperature, but was higher at low temperatures. The values of (c) over cap were threefold lower than previously reported for Antarctic notothenioids and similar to the values for temperate species. The results indicate that the high values of observed during escape behaviour in Antarctic notothenioids are not a universal feature of the suborder. A greater flexion of the body during fast starts is therefore a promising candidate for a specialised feature of behaviour linked to low-temperature performance.</p

Which trophic discrimination factors fit the best? A combined dietary study of a coastal seabird

The use of combined conventional and stable isotope analyses to study the diet of seabirds has become very frequent. Unfortunately species and tissue-specific Trophic Discrimination Factors (TDF), necessary to run stable isotope mixing models in the most performing way, are lacking for a wide number of seabird species. We assessed the process of inspecting and selecting the most adequate TDFs by running mixing region simulations with three different TDFs scenarios. This was carried out in a combined dietary study of a widespread but poorly studied seabird from the Americas: the Neotropic Cormorant (Phalacrocorax brasilianus), at a breeding colony from coastal Patagonia. The mixing models were run with the best fitting carbon and nitrogen TDFs (whole blood), which were those obtained with R package SIDER, a Bayesian inference-based model predicting the TDFs of consumers considering their ecology and phylogenetic relatedness. We found that cormorants fed on rather mobile fish of a fairly variable ecological spectrum, both benthic and pelagic, and showed low prey diversity. Our results coincide with the overall generalist and opportunistic piscivorous habit found at different coastal areas along its broad distribution range. Despite some differences found in the proportion estimates of the main prey between the two methods, their combination through the incorporation of prior information into the mixing models provides a comprehensive trophic profile. Finally, the use of SIDER, alongside the inspection and comparison of different potential TDF values, offered a simple and effective framework to calculate and select the most adequate specific TDFs to be employed in stable isotope mixing models.Bei Ernährungsuntersuchungen an Seevögeln wird immer häufger eine Kombination von konventionellen Analysen mit solchen mit Stabilen Isotopen angewandt. Leider aber fehlen uns für eine große Anzahl von Seevogelarten die art- und gewebespezifschen trophischen Unterscheidungsfaktoren (TDF), die notwendig sind, um Stabile Isotopenmischungs-Modelle mit höchstmöglicher Aussagekraft anzuwenden. Wir bewerteten das Verfahren zur Prüfung und Auswahl der bestgeeigneten TDFs, indem wir Simulationen von Mischregionen mit drei unterschiedlichen TDF-Szenarien laufen ließen. Diese Untersuchung wurde als kombinierte Ernährungsstudie an einer weitverbreiteten, aber nur wenig untersuchten amerikanischen Seevogelart, der neotropischen Humboldtscharbe (Phalacrocorax brasilianus) aus der Familie der Kormorane, in einer Brutkolonie an der Küste Patagoniens durchgeführt. Die Misch-Modelle wurden mit den am besten passenden Kohlenstofund Stickstof-TDFs (aus dem Blut) gerechnet, die wiederum mit SIDER (Stable Isotope Discrimination Estimation in R), einem Bayes’schen Inferenz-basierten Modell zur Vorhersage der TDFs von Konsumenten unter Berücksichtigung ihrer Ökologie und phylogenetischen Verwandtschaft, erstellt wurden. Wir fanden heraus, dass sich die Kormorane von Fischen aus einem breiten ökologischen Spektrum, benthisch und auch pelagisch, ernährten und eine geringe Beutevielfalt zeigten. Unsere Ergebnisse passen gut zu den an unterschiedlichen Küsten mit großen Verbreitungsgebieten gefundenen generellen Angewohnheiten von Fischfressern. Trotz einiger Unterschiede, die wir in den Schätzungen der Anteile der Hauptnahrung zwischen den beiden Methoden fanden, ergibt deren Kombination durch das Einbeziehen früher gewonnener Informationen in die Misch-Modelle doch ein umfassendes trophisches Profl. Schließlich bietet die Anwendung von SIDER zusammen mit der Prüfung und dem Vergleich unterschiedlicher potentieller TDF-Werte einen einfachen und efektiven Rahmen für die Berechnung und Auswahl der am besten passenden, spezifschen TDFs für die Anwendung in Modellen mit gemischten Stabilen Isotopen.Fil: Morgenthaler, Annick. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; ArgentinaFil: Millones, Ana. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; ArgentinaFil: Gandini, Patricia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; ArgentinaFil: Frere, Esteban. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia Austral. Unidad Académica Caleta Olivia. Centro de Investigaciones Puerto Deseado; Argentin

Intra and inter-annual variation in the diet of Magellanic penguin (Spheniscus magellanicus) at Martillo Island, Beagle Channel

Knowledge of seabirds’ diet at each breeding site and its temporal variation is key to understanding and evaluating how changes in marine resources affect each seabird population. In this study, we determined the diet of Magellanic penguins (MP, Spheniscus magellanicus) at Martillo Island, accounting for sex, breeding stage and year. We analyzed a total of 144 stomach contents during three consecutive breeding seasons (2006–2007, 2007–2008 and 2008–2009) and stages (incubation, early and late chick-rearing). MP fed mainly on fuegian sprat (Sprattus fuegensis), which represented 75 % of the biomass consumed by birds during the entire study. The next important prey was squat lobster (Munida gregaria), followed by Patagonian squid (Loligo gahi). Both sexes consumed similar prey items. We observed variation in diet relative composition among breeding years and stages. Fuegian sprat consumption decreased throughout the years whereas squat lobster increased. Penguins consumed a higher proportion of squat lobster and Patagonian squid during the incubation stage than in the chick-rearing stages, whereas fuegian sprat was almost the only prey item consumed during the late chick-rearing stage. MPs show certain flexibility in the use of resources probably as a response to changes in prey populations. Variability in the diet among different reproductive stages could be related to changes in the distribution and abundance of their main prey near the colony during the breeding season together with changes in the energy requirements of seabirds.Fil: Scioscia, Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Raya Rey, Andrea Nélida. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Saenz Samaniego, Ricardo Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Florentin, Olga Viviana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Schiavini, Adrian Carlos Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentin

Oxidative stress in early diabetic nephropathy : fuelling the fire

Original article is available at : http://www.nature.com/ Copyright Nature Publishing Group [Full text of this article is not available in the UHRA]Diabetic nephropathy is a major microvascular complication of diabetes mellitus and the most common cause of end-stage renal disease worldwide. The treatment costs of diabetes mellitus and its complications represent a huge burden on health-care expenditures, creating a major need to identify modifiable factors concerned in the pathogenesis and progression of diabetic nephropathy. Chronic hyperglycemia remains the primary cause of the metabolic, biochemical and vascular abnormalities in diabetic nephropathy. Promotion of excessive oxidative stress in the vascular and cellular milieu results in endothelial cell dysfunction, which is one of the earliest and most pivotal metabolic consequences of chronic hyperglycemia. These derangements are caused by excessive production of advanced glycation end products and free radicals and by the subjugation of antioxidants and antioxidant mechanisms. An increased understanding of the role of oxidative stress in diabetic nephropathy has lead to the exploration of a number of therapeutic strategies, the success of which has so far been limited. However, judicious and timely use of current therapies to maintain good glycemic control, adequate blood pressure and lipid levels, along with lifestyle measures such as regular exercise, optimization of diet and smoking cessation, may help to reduce oxidative stress and endothelial cell dysfunction and retard the progression of diabetic nephropathy until more definitive therapies become available.Peer reviewe