Ocean acidification and temperature rise: effects on calcification during early development of the cuttlefish Sepia officinalis

This study investigated the effects of seawater pH (i.e., 8.10, 7.85 and 7.60) and temperature (16 and 19 °C) on (a) the abiotic conditions in the fluid surrounding the embryo (viz. the perivitelline fluid), (b) growth, development and (c) cuttlebone calcification of embryonic and juvenile stages of the cephalopod Sepia officinalis. Egg swelling increased in response to acidification or warming, leading to an increase in egg surface while the interactive effects suggested a limited plasticity of the swelling modulation. Embryos experienced elevated pCO₂ conditions in the perivitelline fluid (>3-fold higher pCO₂ than that of ambient seawater), rendering the medium under-saturated even under ambient conditions. The growth of both embryos and juveniles was unaffected by pH, whereas ⁴⁵Ca incorporation in cuttlebone increased significantly with decreasing pH at both temperatures. This phenomenon of hypercalcification is limited to only a number of animals but does not guarantee functional performance and calls for better mechanistic understanding of calcification processes.     

Pedestrian fatality and impact speed squared: Cloglog modeling from French national data

Objective: The present study estimates pedestrians' risk of death according to impact speed when hit by a passenger car in a frontal collision.

Methods: Data were coded for all fatal crashes in France in 2011 and for a random sample of 1/20th of all road injuries for the same year and weighted to take into account police underreporting of mild injury. A cloglog model was used to optimize risk adjustment for high collision speeds. The fit of the model on the data was also improved by using the square of the impact speed, which best matches the energy dissipated in the collision.

Results: Modeling clearly demonstrated that the risk of death was very close to 1 when impact speeds exceeded 80 km/h. For speeds less than 40 km/h, because data representative of all crashes resulting in injury were used, the estimated risk of death was fairly low. However, although the curve seemed deceptively flat below 50 km/h, the risk of death in fact rose 2-fold between 30 and 40 km/h and 6-fold between 30 and 50 km/h. For any given speed, the risk of death was much higher for more elderly subjects, especially those over 75 years of age. These results concern frontal crashes involving a passenger car. Collisions involving trucks are far less frequent, but half result in the pedestrian being run over, incurring greater mortality.

Conclusions: For impact speeds below 60 km/h, the shape of the curve relating probability of death to impact speed was very similar to those reported in recent rigorous studies. For higher impact speeds, the present model allows the curve to rise ever more steeply, giving a much better fit to observed data. The present results confirm that, when a pedestrian is struck by a car, impact speed is a major risk factor, thus providing a supplementary argument for strict speed limits in areas where pedestrians are highly exposed.     

Coupling occurs before breakdown during biotransformation of Acid Blue 62 by white rot fungi

Only few data exist on the metabolites produced during the biotransformation of anthraquinonic dyes by white rot fungi (WRF). During the biotransformation of an anthraquinonic dye Acid Blue 62 (ABu62) using Pycnoporus sanguineus MUCL 41582 strain, it was previously demonstrated that the blue colour of the medium turned to red before complete dye decolourisation. To better understand the phenomenon, this study carried out ABu62 biotransformation with five different WRF strains (Coriolopsis polyzona MUCL 38443, Perenniporia ochroleuca MUCL 41114, Perenniporia tephropora MUCL 41562, P. sanguineus MUCL 38531 and Trametes versicolor MUCL 38412) and compared with P. sanguineus MUCL 41582 previously described. A multi-methodological approach (using capillary electrophoresis, mass spectrometry, HPLC, UV, NMR and IR spectroscopies) was developed to characterise the metabolites involved and monitor their apparition. Seven metabolites were commonly found with all strains, suggesting a common metabolic pathway for ABu62 biotransformation. During the first days, dimer and oligomers of the initial ABu62 molecule were observed: the main one absorbed in the 500nm region, explaining the red colour appearance of the medium. This main metabolite was made up of two molecules of ABu62 linked by an azo bond, minus a cyclohexyl moiety. After a longer incubation time, breakdown products were observed. Based on these products characterizations, a bioconversion pathway was proposed.     

Nest excavation in ants: group size effects on the size and structure of tunneling networks

Collective digging activity was studied in the ant Messor sancta Forel in laboratory conditions and with a two dimensional set-up. We analyzed the digging dynamics and topology of tunneling networks excavated by groups of workers ranging from 50 to 200 individuals over 3 days. In all conditions, the dynamics of excavated sand volume were clearly non-linear. Excavation began with an exponential growth and after 3 days reached a saturation phase in which activity was almost totally stopped. The final volume of sand excavated was positively correlated with the number of workers. At the end of the experiments, the two-dimensional tunneling networks were mapped onto planar graphs where the vertices represent small chambers or intersections between tunnels and the edges represent tunnels. We found that all the networks belonged to a same topological family and exhibited several striking invariants such as the distribution of vertex degree that follows a power law. When increasing the number of ants, some changes occurred in the network structure, mainly an increase in the number of edges and vertices, and the progressive emergence of enlarged and highly connected vertices.     

Second trimester two-step trisomy 18 screening using maternal serum markers

Trisomy 21 maternal serum marker screening has led to screening for other anomalies, including trisomy 18. Trisomy 18 is generally prenatally diagnosed because of major morphological defects. However, in up to 30% of cases ultrasound signs are unclear, and in most cases diagnosis is performed late in pregnancy. Of the different maternal serum markers, PAPP-A is now considered as the best for trisomy 18 screening. However, pregnancy-associated plasma protein A (PAPP-A) is of value in first trimester screening for trisomy 21, but not in the second trimester. We therefore propose a two-step screening strategy. Based on 45 trisomy 18 cases, we confirm the values of alpha-fetoprotein (AFP) (median 0.61 MoM), free β-human chorionic gonadotrophin (β-hCG) (median 0.24 MoM) and of PAPP-A (median 0.08 MoM). In the first step, a 0.5 MoM cut-off for AFP or for free β-hCG resulted in detection of 37/45 trisomy 18 cases (82%) with a 10% false-positive rate. The second step consisted of the measurement of PAPP-A for all these false-positive cases. Using a PAPP-A cut-off of 0.5 MoM, all the 37 trisomy 18 cases were detected, but now with a 0.1–0.2% false-positive rate. Amniocentesis was only offered to these few patients. This two-step second trimester screening will be of value for patients who have not been included in first trimester screening based on nuchal translucency (NT) measurement combined with the first trimester markers, PAPP-A and free β-hCG. Copyright © 2002 John Wiley & Sons, Ltd.     

Sequence of quorums during collective decision making in macaques

Synchronization of activity is one of the major challenges of any society, and to what extent social animals reach a consensus still remains to be established. In the case of group movements, recent studies have underlined the importance of the pre-departure period and suggested that some individuals in a group express their motivation to move by showing a preference for a specific direction. However, how do other group members really choose the time and direction of movement? This study shows that in two semi-free ranging Tonkean macaque (Macaca tonkeana) groups, several individuals propose different directions for movement by displaying unique behavior. The whole group eventually moves in the choice of direction supported by the majority of individuals according to a sequence of three quorum rules. Moreover, when the number of individuals choosing another direction is higher than their own group, individuals that proposed alternative directions eventually renounce and follow the majority. Despite conflict of interests, group members reach a consensus before the actual start of group movement. This demonstrates that processes of this type, which can be considered to be voting processes, are not exclusive to human societies and may be explained by a complex sequence of simple rules.     

How do soil and water conservation practices influence climate change impacts on potato production? Evidence from eastern Canada

We used a stochastic production function method together with a farm-level dataset covering 18 farms over a 23-year period to assess the role that soil and water conservation practices play in affecting the climate change impacts on potato yield in northwestern New Brunswick, Canada. Our analysis accounted for the yield effects of farm inputs, farm technologies, farm-specific factors, seasonal climatic variables, soil and water conservation practices, and a series of interaction terms between soil and water conservation practices and climatic variables. Regression results were used in combination with three climate change scenarios developed by the Intergovernmental Panel on Climate Change (A2, A1B, B1) and four general circulation model predictions over three 30-year time periods (2011–2040, 2041–2070, and 2071–2100) to estimate a range of potato yield projections over these time periods. Results show that accounting for soil and water conservation practices in climate–yield relationships increased the impacts of climate change on potato yield, with yield increases of up to 38 % by the 2071–2100 period. These findings provide evidence that adoption of soil and water conservation practices can help boost potato production in a changing Canadian climate.     

Biofiltration of a Mixture of Volatile Organic Emissions

ABSTRACT

Air biofiltration is now under active consideration for the removal of the volatile organic compounds (VOCs) from polluted airstreams. To optimize this emerging environmental technology and to understand compound removal mechanisms, a biofilter packed with peat was developed to treat a complex mixture of VOCs: oxygenated, aromatic, and chlorinated compounds. The removal efficiency of this process was high. The maximum elimination capacity (ECmax) obtained was ~120 g VOCs/m³ peat/hr. Referring to each of the mixture's components, the ECmax showed the limits in terms of biodegradability of VOCs, especially for the halogenated compounds and xylene.

A stratification of biodegradation was observed in the reactor. The oxygenated compounds were metabolized before the aromatic and halogenated ones. Two assumptions are suggested. There was a competition between bacterial communities. Different communities colonized the peat-based biofilter, one specialized for the elimination of oxygenated compounds, the others more specialized for elimination of aromatic and halogenated compounds. There was also substrate competition. Bacterial communities were the same over the height of the column, but the more easily biodegradable compounds were used first for the microorganism metabolism when they were present in the gaseous effluent.     

Characterization of ²⁴¹ Am and ¹³⁴Cs bioaccumulation in the king scallop Pecten maximus: investigation via three exposure pathways

In order to understand the bioaccumulation of ²⁴¹Am and ¹³⁴Cs in scallops living in sediments, the uptake and depuration kinetics of these two elements were investigated in the king scallop Pecten maximus exposed via seawater, food, or sediment under laboratory conditions. Generally, ²⁴¹Am accumulation was higher and its retention was stronger than ¹³⁴Cs. This was especially obvious when considering whole animals exposed through seawater with whole-body concentration factors (CF_7d) of 62 vs. 1, absorption efficiencies (A_0l) of 78 vs. 45 for seawater and biological half-lives (T_b½l) of 892 d vs. 22 d for ²⁴¹Am and ¹³⁴Cs, respectively. In contrast, following a single feeding with radiolabelled phytoplankton, the assimilation efficiency (AE) and T_b½l of ¹³⁴Cs were higher than those of ²⁴¹Am (AE: 28% vs. 20%; T_b½l: 14 d vs. 9 d). Among scallop tissues, the shells always contained the higher proportion of the total body burden of ²⁴¹Am whatever the exposure pathway. In contrast, the whole soft parts presented the major fraction of whole-body burden of ¹³⁴Cs, which was generally associated with muscular tissues. Our results showed that the two radionuclides have contrasting behaviors in scallops, in relation to their physico-chemical properties.     

Collective foraging decision in a gregarious insect

Group foraging by eusocial insects implies sophisticated recruitment processes that often result in collective decisions to exploit the most profitable sources. These advanced levels of cooperation, however, remain limited to a small range of species, and we still know little about the mechanisms underlying group foraging behaviours in the great mass of animals exhibiting lower levels of social complexity. In this paper, we report, for the first time in a gregarious insect, the cockroach Blattella germanica (L.), a collective foraging decision whereby the selection of food sources is reached without requiring active recruitment. Groups of cockroaches given a binary choice between identical food sources exhibited exploitation asymmetries whose amplitude increases with group size. By coupling behavioural observations to computer simulations, we demonstrate that selection of food sources relies uniquely on a retention effect of feeding individuals on newcomers without comparison between available opportunities. This self-organised pattern presents similarities with the foraging dynamics of eusocial species, thus stressing the generic dimension of collective decision-making mechanisms based on social amplification rules despite fundamental differences in recruitment processes. We hypothesise that such parsimony could apply to a wide range of species and help understand the emergence of collective behaviours in simple social systems.