Moose Movement Rates Along Highways and Crossing Probability Models

ABSTRACT We developed and validated a density-adjusted spatial model to predict moose (Alces alces) highway-crossing probability to see if the model could be used as an index of moose-vehicle collision risk. We installed Global Positioning System telemetry collars on 47 moose in the north of the Laurentides Wildlife Reserve, Québec, for 2–36 months. We recorded only 84 highway crossings in spring (0.29% of 28,967 2-hr steps) and 122 crossings in summer (0.18% of 68,337 2-hr steps), despite a high sampling effort and having captured moose close to highways. Moose movement rates during movement steps crossing a highway were on average 3 times higher than during the steps preceding or following highway crossing. Paths used by moose when crossing a highway were characterized by a high proportion of food stands, low proportion of lakes and rivers, and topography typical of a valley. Highway-crossing sites were located in valleys with brackish pools and forest stands providing coniferous cover but a low proportion of lakes and rivers. We adjusted moose crossing probability for local variation in moose density using aerial survey data and assessed crossing probability along the highways in the entire Laurentides Wildlife Reserve. We tested the model using moose-vehicle accident data from 1990 to 2002. The relationship between the density-adjusted crossing probability and number of accidents was relatively loose at the 1-km scale but improved markedly when using longer highway sections (5–15 km; r > 0.80). Our results demonstrate that roads and their surroundings are perceived as low-quality habitat by moose. We also conclude that road segments installed along secondary valleys could be a highly strategic site to deploy mitigation measures such as fences and that it could be desirable to increase the width of road shoulders to reduce forest cover and to eliminate brackish pools to reduce cervid-vehicle collisions. We suggest using empirical data such as location of vehicle-wildlife collisions to plan mitigation measures at a fine scale.     

DISTRIBUTION OF ANNEXIN I DURING NON-PATHOGEN OR PATHOGEN PHAGOCYTOSIS BY CONFOCAL IMAGING AND IMMUNOGOLD ELECTRON MICROSCOPY

Annexin I is an abundant protein in U937 cells differentiated towards a macrophagic phenotype. These cells become able to killEscherichia coli, however, the intracellular pathogenBrucella suis, known to interfere with phagosome maturation, multiply in these differentiated cells. We have analysed by confocal and electron microscopy the cellular localization of annexin I during phagocytosis of yeast, non-pathogenicE. coliand the intracellular pathogenB. suis. Using immunocytochemical detections annexin I was found mainly as patches in the cytoplasm of uninfected cells. Upon phagocytosis of yeast orE. coliorganisms, annexin I rapidly translocated and concentrated around phagosomes. On the other hand, annexin I was never detected around liveB. suis-containing phagosomes. However, when dead brucellae were used, annexin I did translocate to the periphagosomal region. Our results suggest that annexin I could play a role in the molecular mechanism of phagosome maturation, which is impaired by some intracellular pathogens.     

ODOR PERCEPTION OVER LIQUID EMULSIONS CONTAINING SINGLE AROMA COMPOUNDS: EFFECTS OF AROMA CONCENTRATION AND OIL VOLUME FRACTION

This study aimed to check the hypothesis that aroma concentration in the aqueous phase of an oil-in-water emulsion controlled the odor intensity of single aroma compounds. A set of flavored oil-in-water emulsions, prepared according to a 2² experimental design (aroma concentration, oil volume fraction) with two central points, was assessed for odor intensity by a 24-member panel during four sessions. In each session, three of the four-studied aroma molecules (benzaldehyde, ethyl butyrate, linalool and acetophenone) were investigated. Whatever the aroma, the experimental data showed that the oil volume fraction of the emulsion (from 0.12 to 0.48) did not influence the odor intensity. For each emulsion composition, aroma concentrations at equilibrium in both phases were calculated using the oil-water partition coefficient of the compound. Odor intensities, estimated from aroma concentration in the aqueous phase using previously reported modeling of odor intensity above water solutions, were then compared to experimental data. It is confirmed that the perceived odor intensity is governed by the aroma concentration in the aqueous phase at the time of the trial and not by the averaged apparent concentration in the emulsion.     

Abundance and production of bacteria, and relationship to phytoplankton production, in a large tropical lake (Lake Tanganyika)

1. Abundance and bacterial production (BP) of heterotrophic bacteria (HBact) were measured in the north and south basins of Lake Tanganyika, East Africa, during seasonal sampling series between 2002 and 2007. The major objective of the study was to assess whether BP can supplement phytoplankton particulate primary production (particulate PP) in the pelagic waters, and whether BP and particulate PP are related in this large lake. HBact were enumerated in the 0–100 m surface layer by epifluorescence microscopy and flow cytometry; BP was quantified using ³H‐thymidine incorporation, usually in three mixolimnion layers (0–40, 40–60 and 60–100 m). 2. Flow cytometry allowed three subpopulations to be distinguished: low nucleic acid content bacteria (LNA), high nucleic acid content bacteria (HNA) and Synechococcus‐like picocyanobacteria (PCya). The proportion of HNA was on average 67% of total bacterial abundance, and tended to increase with depth. HBact abundance was between 1.2 × 10⁵ and 4.8 × 10⁶ cells mL⁻¹, and was maximal in the 0–40 m layer (i.e. roughly, the euphotic layer). Using a single conversion factor of 15 fg C cell⁻¹, estimated from biovolume measurements, average HBact biomass (integrated over a 100‐m water column depth) was 1.89 ± 1.05 g C m⁻². 3. Significant differences in BP appeared between seasons, especially in the south basin. The range of BP integrated over the 0–100 m layer was 93–735 mg C m⁻² day⁻¹, and overlapped with the range of particulate PP (150–1687 mg C m⁻² day⁻¹) measured in the same period of time at the same sites. 4. Depth‐integrated BP was significantly correlated to particulate PP and chlorophyll‐a, and BP in the euphotic layer was on average 25% of PP. 5. These results suggest that HBact contribute substantially to the particulate organic carbon available to consumers in Lake Tanganyika, and that BP may be sustained by phytoplankton‐derived organic carbon in the pelagic waters.     

Differential response of phytoplankton to additions of nitrogen, phosphorus and iron in Lake Tanganyika

1. In order to evaluate limitation of different phytoplankton groups by inorganic nutrients, multiple nutrient enrichment bioassays using the addition of iron (Fe) and the combined addition of nitrogen and phosphorus (NP) were carried out in the north and the south of Lake Tanganyika during the rainy and dry seasons in 2003 and 2004. 2. Nutrient additions resulted in an increase in phytoplankton growth rate relative to control treatments in all experiments. HPLC pigment data and epifluorescence microscopy counts indicated differential stimulation of the dominant phytoplankton groups. Iron additions mainly stimulated prokaryotic picophytoplankton, while enrichments with nitrogen and phosphorus stimulated green algae and in some cases diatoms. Extended incubation (3 days) indicated co‐limitation of Fe and NP, in particular for picocyanobacteria.     

Abundance and distribution of picoplankton in tropical, oligotrophic Lake Kivu, eastern Africa

1. We used flow cytometry to characterize freshwater photosynthetic picoplankton (PPP) and heterotrophic bacteria (HB) in Lake Kivu, one of the East‐African great lakes. Throughout three cruises run in different seasons, covering the four major basins, phycoerythrin‐rich cells dominated the PPP. Heterotrophic bacteria and PPP cell numbers were always high and spatial variations were modest. This represents an important difference from temperate and high latitude lakes that show high fluctuations in cell abundance over an annual cycle. 2. Three populations of picocyanobacteria were identified: one corresponded to single‐cells (identified as Synechococcus by epifluorescence microscopy, molecular methods and pigment content), and the two other that most probably correspond to two and four celled colonies of the same taxon. The proportion of these two subpopulations was greater under stratified conditions, with stronger nutrient limitation. 3. High PPP concentrations (c. 10⁵ cell mL^?1) relative to HB (c. 10⁶ cell mL^?1) were always found. Lake Kivu supports relatively less bacteria than phytoplankton biomass than temperate systems, probably as a consequence of factors such as temperature, oligotrophy, nutrient limitation and trophic structure. 4. A review of PPP concentration across aquatic systems suggests that the abundance of Synechococcus‐like cyanobacteria in large, oligotrophic, tropical lakes is very high. 5. Photosynthetic picoplankton cell abundances in the oligotrophic tropical lakes Kivu and Tanganyika are comparable to those of eutrophic temperate lakes. This apparently contradicts the view that PPP abundance increases with increasing eutrophy. More data on PPP in tropical lakes are needed to explore further this particular pattern.     

Photosynthesis and Calcification at Cellular, Organismal and Community Levels in Coral Reefs: A Review on Interactions and Control by Carbonate Chemistry

SYNOPSIS. Photosynthesis and calcification in zooxanthellatescleractinian corals and coral reefs are reviewed at severalscales: cellular (pathways and transport mechanisms of inorganiccarbon and calcium), organismal (interaction between photosynthesisand calcification, effect of light) and ecosystemic (communityprimary production and calcification, and air-sea CO₂ exchanges). The coral host plays a major role in supplying carbon for thephotosynthesis by the algal symbionts through a system similarto the carbon-concentrating mechanism described in free livingalgal cells. The details of carbon supply to the calcificationprocess are almost unknown, but metabolic CO₂ seems to be asignificant source. Calcium supply for calcification is diffusionalthrough oral layers, and active membrane transport only occursbetween the calicoblastic cells and the site of calcification.Photosynthesis and calcification are tightly coupled in zooxanthellatescleractinian corals and coral reef communities. Calcificationis, on average, three times higher in light than in darkness.The recent suggestion that calcification is dark-repressed ratherthan light-enhanced is not supported by the literature. Thereis a very strong correlation between photosynthesis and calcificationat both the organism and community levels, but the ratios ofcalcification to gross photosynthesis (0.6 in corals and 0.2in reef communities) differ from unity, and from each otheras a function of level. The potential effect of global climatic changes (pCO₂ and temperature)on the rate of calcification is also reviewed. In various calcifyingphotosynthetic organisms and communities, the rate of calcificationdecreases as a function of increasing pCO₂ and decreasing calciumcarbonate saturation state. The calculated decrease in CaCO₃,production, estimated using the scenarios considered by theInternational Panel on Climate Change (IPCC), is 10% between1880 and 1990, and 9–30% (mid estimate: 22%) from 1990to 2100. Inadequate understanding of the mechanism of calcificationand its interaction with photosynthesis severely limits theability to provide an accurate prediction of future changesin the rate of calcification.     

Evidence for Meiosis in the Testate Amoeba Arcella

ABSTRACT. Electron microscopic studies of Arcella vulgaris have revealed a sexual process occurring in cysts. The evidence includes: I) synaplonemal complexes in prophasic nuclei. 2) two consecutive divisions different from vegetative mitosis, 3) degeneration of certain products of these nuclear divisions, and 4) fusion of nuclei indicating karyogamy. The process is apparently autogamy preceded by a two-division meiosis. The testate amoebae can no longer be considered asexual.