A model for the neuronal substrate of dead reckoning and memory in arthropods: a comparative computational and behavioral study

Returning to the point of departure after exploring the environment is a key capability for most animals. In the absence of landmarks, this task will be solved by integrating direction and distance traveled over time. This is referred to as path integration or dead reckoning. An important question is how the nervous systems of navigating animals such as the 1 mm³ brain of ants can integrate local information in order to make global decision. In this article we propose a neurobiologically plausible system of storing and retrieving direction and distance information. The path memory of our model builds on the well established concept of population codes, moreover our system does not rely on trigonometric functions or other complex non-linear operations such as multiplication, but only uses biologically plausible operations such as integration and thresholding. We test our model in two paradigms; in the first paradigm the system receives input from a simulated compass, in the second paradigm, the model is tested against behavioral data recorded from 17 ants. We were able to show that our path memory system was able to reliably encode and compute the angle of the vector pointing to the start location, and that the system stores the total length of the trajectory in a dependable way. From the structure and behavior of our model, we derive testable predictions both at the level of observable behavior as well as on the anatomy and physiology of its underlying neuronal substrate.     

A new species of Eupatorium (Asteraceae) from the Philippines

Eupatorium leonardii, presently known only from Mt. Mingan in the border region between Aurora and Nueva Ecija Provinces in Luzon, Philippines, is described and illustrated. The new species is remarkable because it is the only woody representative of the genus with a peculiar spiral phyllotaxy. Previously, Eupatorium s. str. consisted of herbs with opposite or verticillate phyllotaxy.     

Renal function at hospital admission and mortality due to acute kidney injury after myocardial infarction

Background

The role of an impaired estimated glomerular filtration rate (eGFR) at hospital admission in the outcome of acute kidney injury (AKI) after acute myocardial infarction (AMI) has been underreported. The aim of this study was to assess the influence of an admission eGFR<60 mL/min/1.73 m² on the incidence and early and late mortality of AMI-associated AKI.

Methods

A prospective study of 828 AMI patients was performed. AKI was defined as a serum creatinine increase of ≥50% from the time of admission (RIFLE criteria) in the first 7 days of hospitalization. Patients were divided into subgroups according to their eGFR upon hospital admission (MDRD formula, mL/min/1.73 m²) and the development of AKI: eGFR≥60 without AKI, eGFR<60 without AKI, eGFR≥60 with AKI and eGFR<60 with AKI.

Results

Overall, 14.6% of the patients in this study developed AKI. The admission eGFR had no impact on the incidence of AKI. However, the admission eGFR was associated with the outcome of AMI-associated AKI. The adjusted hazard ratios (AHR, Cox multivariate analysis) for 30-day mortality were 2.00 (95% CI 1.11–3.61) for eGFR<60 without AKI, 4.76 (95% CI 2.45–9.26) for eGFR≥60 with AKI and 6.27 (95% CI 3.20–12.29) for eGFR<60 with AKI. Only an admission eGFR of <60 with AKI was significantly associated with a 30-day to 1-year mortality hazard (AHR 3.05, 95% CI 1.50–6.19).

Conclusions

AKI development was associated with an increased early mortality hazard in AMI patients with either preserved or impaired admission eGFR. Only the association of impaired admission eGFR and AKI was associated with an increased hazard for late mortality among these patients.     

Conserved metallomics in two insect families evolving separately for a hundred million years

Μetal cofactors are required for enzymatic catalysis and structural stability of many proteins. Physiological metal requirements underpin the evolution of cellular and systemic regulatory mechanisms for metal uptake, storage and excretion. Considering the role of metal biology in animal evolution, this paper asks whether metal content is conserved between different fruit flies. A similar metal homeostasis was previously observed in Drosophilidae flies cultivated on the same larval medium. Each species accumulated in the order of 200 µg iron and zinc and approximately ten-fold less manganese and copper per gram dry weight of the adult insect. In this paper, data on the metal content in fourteen species of Tephritidae, which are major agricultural pests worldwide, are presented. These fruit flies can be polyphagous (e.g., Ceratitis capitata) or strictly monophagous (e.g., Bactrocera oleae) or oligophagous (e.g., Anastrepha grandis) and were maintained in the laboratory on five distinct diets based on olive oil, carrot, wheat bran, zucchini and molasses, respectively. The data indicate that overall metal content and distribution between the Tephritidae and Drosophilidae species was similar. Reduced metal concentration was observed in B. oleae. Feeding the polyphagous C. capitata with the diet of B. oleae resulted in a significant quantitative reduction of all metals. Thus, dietary components affect metal content in some Tephritidae. Nevertheless, although the evidence suggests some fruit fly species evolved preferences in the use or storage of particular metals, no metal concentration varied in order of magnitude between these two families of Diptera that evolved independently for over 100 million years.     

How ethnobotany can aid biodiversity conservation: reflections on investigations in the semi-arid region of NE Brazil

Ethnobotany is a relatively new discipline but its social and scientific roles are becoming more consistently defined and its importance as a tool for complimenting management and conservation strategies at local and regional levels is now well recognized by the scientific community throughout the world. In the present work we have collected information from four years of ethnobotanical study in an area of caatinga vegetation in the semi-arid region of northeastern Brazil with the goal of defining a model for conservation and management actions in the region. Drawing on ethnobotanical and ecological information obtained through traditional techniques of ethnobotanical and vegetation surveys, we discuss the uses of 166 native and exotic plant species and suggest specific actions and specific groups of species for conservation and sustainable use programs. We also discuss the limitations of our approach and indicate what information must still be collected in order to construct robust and workable plans of action.     

The Inclusion and Selection of Medicinal Plants in Traditional Pharmacopoeias—Evidence in Support of the Diversification Hypothesis

The Inclusion and Selection of Medicinal Plants in Traditional Pharmacopoeias—Evidence in Support of the Diversification Hypothesis. An ethnobotanical study with phytochemical analyses was undertaken to examine the medicinal plants used by residents of a small rural community in northeastern Brazil. The present work tested two ideas that attempt to explain the inclusion and selection of medicinal plants in a given culture: the diversification hypothesis and the concept of versatility. The study involved 101 people and used semistructured interviews. A total of 61 plants were selected, including 25 exotic and 36 native species. Plants were classified according to their habit and analyzed for their phytochemical components. In addition, the relative importance (RI) of these plants was calculated, and a chemical diversity index (CDI) was created and applied to each of the species. Exotic and native plants were found to have significantly different occurrences of certain classes of compounds; this result supports the diversification hypothesis. It was therefore concluded that exotic plants are included in traditional pharmacopoeias to fill therapeutic vacancies that native plants cannot satisfy.     

Traditional Knowledge and Management of Umbu (<Emphasis Type="Italic">Spondias tuberosa</Emphasis>, Anacardiaceae): An Endemic Species from the Semi–Arid Region of Northeastern Brazil

Traditional Knowledge and Management of Umbu ( Spondias tuberosa , Anacardiaceae): An Endemic Species from the Semi–Arid Region of Northeastern Brazil. Spondias tuberosa, or umbu, is an arboreal species that is important both as an alternative economic and subsistence resource for rural communities in the semi–arid, northeastern regions of Brazil. The aim of this work was to study the knowledge, uses, local gathering practices, and management systems of S. tuberosa that are part of the traditions of the communities in this region. An ethnobotanical survey was conducted in two stages in a rural community in the state of Pernambuco. In the first stage, all of the dwellings were visited and both the men and the women who were responsible for their house were interviewed. In the second stage, people who were identified as having a direct relationship with the resource were questioned more thoroughly about the species. Knowledge of S. tuberosa is equally distributed in the community; there are no significant differences in knowledge between men and women, or across age groups. The food category is the most important for both human and animal nourishment. The main forms of local management are tolerance and gathering of fruit. Fruit gathering is directly affected by, in order of importance, taste (sweet–sour), size, and quantity of fruit pulp. The usefulness of S. tuberosa contributes considerably to the tolerance of this species in both managed areas and as part of the native vegetation.     

Comparative genomic analysis of magnetotactic bacteria from the Deltaproteobacteria provides new insights into magnetite and greigite magnetosome genes required for magnetotaxis

Magnetotactic bacteria (MTB) represent a group of diverse motile prokaryotes that biomineralize magnetosomes, the organelles responsible for magnetotaxis. Magnetosomes consist of intracellular, membrane‐bounded, tens‐of‐nanometre‐sized crystals of the magnetic minerals magnetite (Fe₃O₄) or greigite (Fe₃S₄) and are usually organized as a chain within the cell acting like a compass needle. Most information regarding the biomineralization processes involved in magnetosome formation comes from studies involving Alphaproteobacteria species which biomineralize cuboctahedral and elongated prismatic crystals of magnetite. Many magnetosome genes, the mam genes, identified in these organisms are conserved in all known MTB. Here we present a comparative genomic analysis of magnetotactic Deltaproteobacteria that synthesize bullet‐shaped crystals of magnetite and/or greigite. We show that in addition to mam genes, there is a conserved set of genes, designated mad genes, specific to the magnetotactic Deltaproteobacteria, some also being present in Candidatus Magnetobacterium bavaricum of the Nitrospirae phylum, but absent in the magnetotactic Alphaproteobacteria. Our results suggest that the number of genes associated with magnetotaxis in magnetotactic Deltaproteobacteria is larger than previously thought. We also demonstrate that the minimum set of mam genes necessary for magnetosome formation in Magnetospirillum is also conserved in magnetite‐producing, magnetotactic Deltaproteobacteria. Some putative novel functions of mad genes are discussed.     

Identity and change: The example of the falashas,between assimilation in Ethiopia and integration in Israel

Daniel Friedmann is a Research Fellow at the C.N.R.S., Paris. Ulysses Santamaria is a Fellow at the Maison des Sciences de L'Homme, Paris.