Spatial distribution patterns of ascidians (Ascidiacea: Tunicata) on the continental shelves off the northern Antarctic Peninsula

Ascidians (Ascidiacea: Tunicata) are sessile suspension feeders that represent dominant epifaunal components of the Southern Ocean shelf benthos and play a significant role in the pelagic–benthic coupling. Here, we report the results of a first study on the relationship between the distribution patterns of eight common and/or abundant (putative) ascidian species, and environmental drivers in the waters off the northern Antarctic Peninsula. During RV Polarstern cruise XXIX/3 (PS81) in January–March 2013, we used seabed imaging surveys along 28 photographic transects of 2 km length each at water depths from 70 to 770 m in three regions (northwestern Weddell Sea, southern Bransfield Strait and southern Drake Passage), differing in their general environmental setting, primarily oceanographic characteristics and sea-ice dynamics, to comparatively analyze the spatial patterns in the abundance of the selected ascidians, reliably to be identified in the photographs, at three nested spatial scales. At a regional (100-km) scale, the ascidian assemblages of the Weddell Sea differed significantly from those of the other two regions, whereas at an intermediate 10-km scale no such differences were detected among habitat types (bank, upper slope, slope, deep/canyon) on the shelf and at the shelf break within each region. These spatial patterns were superimposed by a marked small-scale (10-m) patchiness of ascidian distribution within the 2-km-long transects. Among the environmental variables considered in our study, a combination of water-mass characteristics, sea-ice dynamics (approximated by 5-year averages in sea-ice cover in the region of or surrounding the photographic stations), as well as the seabed ruggedness, was identified as explaining best the distribution patterns of the ascidians.     

Antioxidant Defenses of Francisella tularensis Modulate Macrophage Function and Production of Proinflammatory Cytokines

Francisella tularensis, the causative agent of a fatal human disease known as tularemia, has been used in the bioweapon programs of several countries in the past, and now it is considered a potential bioterror agent. Extreme infectivity and virulence of F. tularensis is due to its ability to evade immune detection and to suppress the host''s innate immune responses. However, Francisella-encoded factors and mechanisms responsible for causing immune suppression are not completely understood. Macrophages and neutrophils generate reactive oxygen species (ROS)/reactive nitrogen species as a defense mechanism for the clearance of phagocytosed microorganisms. ROS serve a dual role; at high concentrations they act as microbicidal effector molecules that destroy intracellular pathogens, and at low concentrations they serve as secondary signaling messengers that regulate the expression of various inflammatory mediators. We hypothesized that the antioxidant defenses of F. tularensis maintain redox homeostasis in infected macrophages to prevent activation of redox-sensitive signaling components that ultimately result in suppression of pro-inflammatory cytokine production and macrophage microbicidal activity. We demonstrate that antioxidant enzymes of F. tularensis prevent the activation of redox-sensitive MAPK signaling components, NF-κB signaling, and the production of pro-inflammatory cytokines by inhibiting the accumulation of ROS in infected macrophages. We also report that F. tularensis inhibits ROS-dependent autophagy to promote its intramacrophage survival. Collectively, this study reveals novel pathogenic mechanisms adopted by F. tularensis to modulate macrophage innate immune functions to create an environment permissive for its intracellular survival and growth.     

Dimorphism and divergence in island and mainland Anoles

Relative to the West Indies, the ecology and evolution of anoles inhabiting islands off Central and South America have received little attention. The paucity of studies on continental islands has limited our ability to generalize and extend results based on the West Indian paradigm, as well as our understanding of the profound differences between the adaptive radiations of continental vs. Greater Antillean anoles. Here we compare the morphological, ecological, behavioural and genetic divergence between Anolis nebulosus populations inhabiting a small island in the Bay of Chamela, Mexico, and a nearby mainland forest. Notably, the two populations exhibit intra‐sexual dimorphism with respect to head and limb sizes, the first such polymorphism documented for an Anolis species. We also compare the shape of island and mainland A. nebulosus with each other, the six West Indian ecomorphs and a hypothetical generalist species. Finally, we address the generalist convergence hypothesis for anoles on single species islands. We conclude that convergence on a generalist morphology is widespread among solitary anoles in the West Indies. We present data on a limited sample of solitary anoles with mainland ancestors that suggest a parallel convergence on a similar generalist morphology, probably due to similar adaptive landscapes shaped by selective forces common to small island environments.     

In the path of the Hurricane: impact of Hurricane Irene and Tropical Storm Lee on watershed hydrology and biogeochemistry from North Carolina to Maine,USA

Although many climate predictions suggest that the frequency and intensity of large storm events might increase in the coming decades, few studies document the full impact of such events along their path. Here, we synthesize information on the impact of Hurricane Irene (formed August 21 2011) and Tropical Storm Lee (formed August 30, 2011) on erosion and sediment transport, lake metabolism, riparian hydrology and biogeochemistry, and stream water quality, from North Carolina to Maine. In almost all cases, these storms generated unprecedented changes in water quality (concentrations, loads), from tenfold increases in DOC and 100-fold increases in POC in Maryland, to 100-fold increases in TSS concentrations in Pennsylvania. Overbank flooding and up to 200-year streamflow events were recorded in New York and Vermont. In many cases, particulate loads (e.g. POC, PP, TSS) occurring during Irene and Lee represented more than 30% of the annual load. The dominance of particulate exports over solutes during Irene and Lee is consistent with the mobilization of normally immobile sediment pools, and massive erosion as reported at many locations across the Northeastern US. Several studies reported long lasting (> 1 year) effects of Irene and Lee on cyanobacterial blooms, erosion, or stream suspended sediment concentrations. However, this review also highlighted the lack of a consistent strategy in terms of methods, and measured water quality parameters. This strongly hinders our ability to fully assess the large-scale impact of such events on our environment, and ultimately their impact on our economy and society.     

Application of trace metal analysis to basic problems in neurobiology studies of patients with Reye’s syndrome

Reye’s syndrome (Rs) is an acute illness in children manifested by encephalopathy and fatty degeneration of the liver. The syndrome may be secondary to injury of mitochondria following a toxic insult in a susceptible individual with a viral illness. Since the response to infection often involves a change in trace metals, we investigated the metal status of patients with Rs. Decreased levels of serum and liver selenium (Se) and copper (Cu) were demonstrated via PIXE analysis, in addition to an increase in serum iron (Fe) and zinc (Zn). In a subsequent study using a rat animal model of Rs, the hepatotoxin 4-pentenoic acid (4-PA) produced similar changes in serum and liver trace metals. Serum and liver Se levels were also significantly depleted in rats exposed to another toxin, valproic acid (VPA). Aspirin, known to complex metals, may also be associated with Rs. Rats chronically exposed to aspirin had decreased serum Se, Fe, and Zn compared to controls. Selenium was also decreased in liver, as was Cu. Atomic absorption spectrophotometric analysis of serum and liver Cu for mice exposed to aspirin and influenza A virus were also studied. In liver, Cu was significantly decreased in mice on Cu-deficient diets but, not in control mice exposed to virus, or aspirin and virus. For the Se-deficient animals, liver Cu was not different from controls, but there was an increase in tissue Cu for Se-sufficient mice exposed to virus and aspirin; Cu levels were decreased in sera of this latter group. Serum Cu was increased in Cu-sufficient mice exposed to virus and aspirin. The above data are of biologic and toxicologic interest because of metalloenzyme localization in the mitochondrial matrix, the cellular compartment showing the greatest degree of pathologic change in Rs. In particular, Se-dependent gluthathione peroxidase is a major deterent of peroxidative damage of lipid membranes. The accumulated evidence suggests that alteration of trace metals, e.g., decrease in Se, may promote peroxidation of mitochondrial membranes in patients with Rs.     

Serum cholesterol and triglyceride levels in Scyliorhinus canicula (L.) during sexual maturation

A study was carried out on the serum levels of cholesterol [total (TC) and that associated with high-density lipoproteins (HDLC)] and triglyceride (TG) in 127 specimens of Scyliorhinus canicula . The values obtained were correlated with sex, size, liver weight and reproductive stage. Results showed that male dogfish have higher levels of TC and HDLC, and lower TG than female. In adult males, TC increased and HDLC decreased with both size and spermatogenesis. Females carrying capsulated eggs showed a noticeable increase in TG together with a decrease of the HDLC levels, which were apparently not related with size.