Lack of population structure in the fiddler crab Uca annulipes along an East African latitudinal gradient: genetic and morphometric evidence

Phylogeographic patterns in Uca annulipes sampled from 30 locations across an East African latitudinal gradient were investigated using mitochondrial DNA cytochrome oxidase I sequences and analysed together with patterns of morphometric differentiation. Four hundred and four specimens along the east African coast were sampled, and 18 haplotypes were encountered. Haplotype and nucleotide diversity values were very low and the phylogenetic analysis did not reveal any clear phylogeographic structure. Furthermore, the analysis of molecular variance and pairwise Φ _ST values showed no significant spatial population differentiation. Mismatch analyses and tests of neutrality supported the hypothesis that this species has undergone a fairly recent demographic expansion. Our results, therefore, failed to demonstrate significant geographical structure in the pattern of genetic variation, indicating that populations of U. annulipes are capable of extensive gene flow among mangroves along the coast. The genetic structure of this species could be panmictic due to a high amount of gene flow along the geographical gradient in study during the planktonic larval phase, when larvae are carried along stream by the dominant currents. Moreover, the morphometric analysis performed did not reveal differences of shape differentiation according to a geographical pattern, although significant differences among the sampling areas were found.     

Growth pattern of the sea urchin, Loxechinus albus (Molina, 1782) in southern Chile: evaluation of growth models

The growth pattern of Loxechinus albus in southern Chile was studied using size-at-age data obtained by reading growth bands on the genital plates. The scatter plots of sizes-at-age for samples collected in three different locations indicated that growth is linear between ages 2 and 10. Five different growth models, including linear, asymptotic and non-asymptotic functions, were fitted to the data, and model selection was conducted based on the Akaike information criteria (AIC) and the Bayesian information criteria (BIC). The AIC identified the Tanaka model as the most suitable for two of the three sites. However, the BIC led to the selection of the linear model for all zones. Our results show that the growth pattern of L. albus is different from the predominantly asymptotic pattern that has been reported for other sea urchin species.     

Modelling the effects of extreme events on the dynamics of the amphipod Corophium orientale

The brackish water amphipod Corophium orientale is the dominant macroinvertebrate species in the upper Mira estuary, a small mesotidal system located in the southwest coast of Portugal. As climate changes will increase the frequency and intensity of extreme events such as floods and droughts, these will have a negative effect on benthic estuarine invertebrates, namely C. orientale. In order to understand the effects of these events on C. orientale, a dynamic model, based on published information and calibrated with field data, was developed and different scenarios were tested.For model construction, the annual development of three cohorts of C. orientale, their growth rates, and the establishment of the timing of each cohort rise and extinction are introduced. This structure can be repeated indefinitely, for years, and few parameters are required. The model simulations highlight the need for refuge areas that enable a fast recovery of the amphipod population after an extreme event and the recolozination of the affected areas.     

Removal of metal ions from aqueous solution by chelating polymeric hydrogel

Polysaccharide natural seed coat from the tree Magonia pubescens, in the form of hydrogel was used to remove metals in aqueous solution. Swelling tests indicate that seed coat presents hydrogel behavior, with maximum water absorption of 292 g water/g. Adsorption experiments performed using Na⁺, Mg²⁺, K⁺, Ca²⁺, Cr³⁺, Fe³⁺ and Zn²⁺ demonstrated that the polysaccharide structure has a high capacity to extract these ions from the aqueous solution. Scanning electron microscopy revealed significant morphological changes of the material before and after water contact. Differential scanning calorimetry measurements indicate a signal shift of the water evaporation temperature in the material with adsorbed zinc. X-ray photoelectron spectroscopy analysis combined with theoretical studies by the density functional theory and on Hartree–Fock (HF) level evidence that the metallic ions were adsorbed through coordination with hydroxyl groups of polysaccharide. In the case of Zn²⁺ the lowest HF energy was observed for the tetracoordination mode, where Zn²⁺ is coordinated by two hydroxyl groups and two water molecules.     

The need to look beyond the production and provision of relief seed: experiences from southern Sudan

Free distribution of seeds in selected areas of southern Sudan has been widespread as a way of increasing food security. Field research in areas targeted for seed relief found that farmer seed systems continue to meet the crop and varietal needs of farmers even following the 1998 famine. Donor investments in seed multiplication of improved sorghum have not been sustained due to a lack of effective demand for the improved seed beyond that created by the relief agencies. The article argues that rather than imposing outside solutions, whether through seed provisioning or seed production enterprises, greater attention needs to be given to building on the strengths of existing farmer systems and designing interventions to alleviate the weaknesses. The case is made to support dynamically the process of farmer experimentation through the informed introduction of new crops and varieties that can potentially reinforce the strength and diversity of local cropping systems.     

Antecedents of fatigue, close calls, and crashes among commercial motor-vehicle drivers

PROBLEM: Minimizing driver fatigue among commercial motor-vehicle (CMV) drivers is a major safety issue in the United States. This study examines the effects of potentially fatigue-inducing factors inherent in truck driving work and company safety management in explaining: (a) drivers driving while fatigued, (b) the frequency of close calls due to fatigue, and (c) actual crashes among CMV drivers. METHOD: Data for this study are derived from a survey of CMV drivers in 116 trucking firms, with all data being driver-reported. The relative roles of fatigue-inducing factors and safety management practices in explaining variation in fatigue, close calls, and crashes are reported, along with the roles of fatigue in affecting close calls and crashes via hierarchical regression. RESULTS: Findings indicated that fatigue-inducing factors inherent in driving work and safety practices accounted for appreciable variation in driving fatigued (R(2) =.42) and close calls (R(2) =.35), but not crash involvement. Driving while fatigued also accounted for incremental increases in the amount of variation in close calls, after consideration of inherent factors and safety practices. IMPACT ON INDUSTRY: Findings indicate that safety practices (e.g., establishment of a strong safety culture, dispatcher scheduling practices, company assistance with fatiguing behaviors such as loading and unloading) have considerable potential to offset fatigue-inducing factors associated with truck driving work.     

Management practices as antecedents of safety culture within the trucking industry: similarities and differences by hierarchical level

PROBLEM: A homogeneous perception of safety is important for the achievement of a strong safety culture; however, employees may differ in their safety perceptions, depending on their position and/or hierarchical level within the organization. Moreover, there is limited information on the antecedents of safety culture. This study examines how safety training, driver scheduling autonomy, opportunity for safety input, and management commitment to safety influence individuals' perceptions of safety culture. METHOD: Data for this study were drawn from 116 trucking firms, stratified by three safety performance levels. The data were collected from drivers (lowest hierarchical level), dispatchers (medium hierarchical level), and safety directors (highest hierarchical level), regarding their perceptions of their respective corporate safety cultures. Perceptions of safety culture were analyzed through a linear regression using dummy variables to differentiate among the three hierarchical groups. The resulting model allowed for examination of the specific antecedents of safety culture for the three employee groups and the extent to which the hierarchical groups were in agreement with each other. RESULTS: Driver fatigue training, driver opportunity for safety input, and top management commitment to safety were perceived to be integral determinants of safety culture in all three groups. IMPACT ON INDUSTRY: Trucking firms seeking to strengthen employees' perceptions of safety culture might begin by improving these safety management practices while appreciating that they may have a different impact depending on the employee's hierarchical position (e.g., drivers' perceptions of safety culture are more influenced by top management commitment and driver fatigue training). A fourth safety practice examined, driver scheduling autonomy, was not found to be instrumental in shaping safety culture for any of the three hierarchical levels. Consistent with previous research, implementation of stronger safety cultures should result in fewer accidents.     

Organic chlorine compounds in lake sediments. V. Bottom of Baikal near a pulp mill

Organically bound chlorine (OCl) together with inorganic chloride (Cl⁻) was measured from bottom surface samples of the Lake Baikal near a pulp mill and compared to organic matter contents (OM). Although total contents of OCl, Cl⁻ and OM were much lower than, the ratio of OCl to OM was of the same order of magnitude as in pulp mill recipients of Finland.