Zooplankton of Lake Kivu, East Africa, half a century after the Tanganyika sardine introduction

The introduction into Lake Kivu of the planktivorous fish Limnothrissamiodon at the end of the 1950s raised major concern about thefate of mesozooplankton, but few data were available to assessthe impact of predation. In this study, we followed zooplanktonvariations in Lake Kivu for 3.5 years. Present Lake Kivu mesozooplanktonis dominated by cyclopoid copepods (Thermocyclops consimilis,Mesocyclops aequatorialis and Tropocyclops confinis), but cladoceransand rotifers are also present. Each year, total crustacean abundancein the plankton increased to a distinct seasonal maximum followinga rise of phytoplankton production associated with a deep epilimneticmixing in the dry season (August–September). This dependenceon phytoplankton resource suggests that mesozooplankton dynamicsin Lake Kivu is mainly bottom-up controlled, contrary to expectationsfrom the food web structure. However, measurements of body sizeindicate that sardine predation affects the cladoceran Diaphanosomaexcisum, whereas the larger copepods may efficiently escapepredation by migration in the deep mixolimnion at daytime. Totalbiomass of mesozooplankton in Lake Kivu is lower than in lakesTanganyika and Malawi. This may be related to the disappearanceof a large grazer that existed before the sardine introduction,whereas the large lakes of the same region have a more complexpelagic food web, with piscivorous fish, and with calanoid copepods,which can more efficiently exploit phytoplankton production.     

Habitat selection and abundance of common genets <Emphasis Type="Italic">Genetta genetta</Emphasis> using camera capture-mark-recapture data

Using camera-trapping techniques, the present study, conducted from 2005 to 2007, provides common genet abundance estimates in Serra da Malcata Nature Reserve (central-eastern Portugal). We estimated genet abundance using the software CAPTURE. It was possible to obtain a capture success of 1.49 captures/100 trap-nights. Considering the heterogeneity model (M_h), which presents higher biological significance, the estimated density varied between 0.50 (95% CI = 0.43–0.56 genets/km²) to 0.92 (95% CI = 0.87–0.97 genets/km²) genets/km² with an average density value of 0.70 genets/km² (95% CI = 0.58–0.82 genets/km²). These estimates emphasized this technique as a reliable method for assessing average genet density over large spatial scales and for monitoring future changes in genet numbers. In terms of habitat selection, genets selected Quercus rotundifolia and Arbutus unedo woodlands and avoided Erica spp. and Cistus ladanifer scrubland and Eucalyptus stands. Considering the landscape heterogeneity outside the reserve, our study emphasizes the importance of the protected area for small carnivore conservation.     

Unfolding of cardosin A in organic solvents and detection of intermediaries

In the present study the relationship between conformational stability and enzymatic activity in the presence of organic solvents (OS) was investigated. We have found that cardosin A, the model protease investigated in this work, inactivates through a biphasic mechanism, which is incipient in aqueous buffer and becomes visible in the presence of hydrophilic OS. In fact, in OS this inactivation originates stable intermediaries that were detected in acetonitrile. This biphasic mechanism can be described in two phases: an initial one, where OS induce alterations that affect the active site cleft and global mobility, but with little interference on the global protein conformation, and, a second phase, where there is a global change in protein conformation with concomitant activity loss. It is shown that in the presence of hydrophilic OS there is a larger mobility of the enzyme, revealed by limited proteolysis, probably due to a weakening of hydrophobic interactions within the protein core.     

Mammalian membrane trafficking as seen through the lens of bacterial toxins

A fundamental question of eukaryotic cell biology is how membrane organelles are organised and interact with each other. Cell biologists address these questions by characterising the structural features of membrane compartments and the mechanisms that coordinate their exchange. To do so, they must rely on variety of cargo molecules and treatments that enable targeted perturbation, localisation, and labelling of specific compartments. In this context, bacterial toxins emerged in cell biology as paradigm shifting molecules that enabled scientists to not only study them from the side of bacterial infection but also from the side of the mammalian host. Their selectivity, potency, and versatility made them exquisite tools for uncovering much of our current understanding of membrane trafficking mechanisms. Here, we will follow the steps that lead toxins until their intracellular targets, highlighting how specific events helped us comprehend membrane trafficking and establish the fundamentals of various cellular organelles and processes. Bacterial toxins will continue to guide us in answering crucial questions in cellular biology while also acting as probes for new technologies and applications.     

Climate change in tropical fresh waters (comment on the paper ‘Plankton dynamics under different climatic conditions in space and time’ by de Senerpont Domis et al., )

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Relative contribution of biotic and abiotic factors to the population density of the cassava green mite, Mononychellus tanajoa (Acari: Tetranychidae)

The cassava green mite, Mononychellus tanajoa, is a key pest of cassava, Manihot esculenta Crantz (Euphorbiaceae), and it may be kept in check by naturally occurring predatory mites of the family Phytoseiidae. In addition to predatory mites, abiotic factors may also contribute to regulate pest mite populations in the field. Here, we evaluated the population densities of both M. tanajoa and the generalist predatory mite Euseius ho DeLeon (Acari: Phytoseiidae) over the cultivation cycle (11 months) of cassava in four study sites located around the city of Miranda do Norte, Maranhão, Brazil. The abiotic variables rainfall, temperature and relative humidity were also recorded throughout the cultivation cycle of cassava. We determined the relative importance of biotic (density of E. ho) and abiotic (rainfall, temperature and relative humidity) factors to the density of M. tanajoa. The density of M. tanajoa increased whereas the density of E. ho remained constant throughout time. A hierarchical partitioning analysis revealed that most of the variance for the density of M. tanajoa was explained by rainfall and relative humidity followed by E. ho density and temperature. We conclude that abiotic factors, especially rainfall, were the main mechanisms driving M. tanajoa densities.     

Impacts of past habitat loss and future climate change on the range dynamics of South African Proteaceae

Aim

To assess how habitat loss and climate change interact in affecting the range dynamics of species and to quantify how predicted range dynamics depend on demographic properties of species and the severity of environmental change.

Location

South African Cape Floristic Region.

Methods

We use data‐driven demographic models to assess the impacts of past habitat loss and future climate change on range size, range filing and abundances of eight species of woody plants (Proteaceae). The species‐specific models employ a hybrid approach that simulates population dynamics and long‐distance dispersal on top of expected spatio‐temporal dynamics of suitable habitat.

Results

Climate change was mainly predicted to reduce range size and range filling (because of a combination of strong habitat shifts with low migration ability). In contrast, habitat loss mostly decreased mean local abundance. For most species and response measures, the combination of habitat loss and climate change had the most severe effect. Yet, this combined effect was mostly smaller than expected from adding or multiplying effects of the individual environmental drivers. This seems to be because climate change shifts suitable habitats to regions less affected by habitat loss. Interspecific variation in range size responses depended mostly on the severity of environmental change, whereas responses in range filling and local abundance depended mostly on demographic properties of species. While most surviving populations concentrated in areas that remain climatically suitable, refugia for multiple species were overestimated by simply overlying habitat models and ignoring demography.

Main conclusions

Demographic models of range dynamics can simultaneously predict the response of range size, abundance and range filling to multiple drivers of environmental change. Demographic knowledge is particularly needed to predict abundance responses and to identify areas that can serve as biodiversity refugia under climate change. These findings highlight the need for data‐driven, demographic assessments in conservation biogeography.

     

Lipid metabolism modulation by the P2X7 receptor in the immune system and during the course of infection: new insights into the old view

For decades, scientists have described numerous protein pathways and functions. Much of a protein’s function depends on its interactions with different partners, and those partners can change depending on the cell type or system. The P2X7 receptor (P2X7R) is one such multifunctional protein that is related to multiple partners and signaling pathways. The relationship between P2X7R and different enzymes involved in lipid metabolism represents a relatively new field in P2X7R research. This field of research began in epithelial cells and currently includes immune and nervous cells. The P2X7R-lipid metabolism pathway is related to many biological functions of P2X7R, such as cell death and pathogen clearance, and this signaling pathway may be involved in many functions that are dependent on bioactive lipids. In the present review, we will attempt to summarize data related to the P2X7R-lipid metabolism pathway, focusing on signaling pathways and their biological relevance to the immune system and infection.