Accounting for imperfect detection of groups and individuals when estimating abundance

If animals are independently detected during surveys, many methods exist for estimating animal abundance despite detection probabilities <1. Common estimators include double‐observer models, distance sampling models and combined double‐observer and distance sampling models (known as mark‐recapture‐distance‐sampling models; MRDS). When animals reside in groups, however, the assumption of independent detection is violated. In this case, the standard approach is to account for imperfect detection of groups, while assuming that individuals within groups are detected perfectly. However, this assumption is often unsupported. We introduce an abundance estimator for grouped animals when detection of groups is imperfect and group size may be under‐counted, but not over‐counted. The estimator combines an MRDS model with an N‐mixture model to account for imperfect detection of individuals. The new MRDS‐Nmix model requires the same data as an MRDS model (independent detection histories, an estimate of distance to transect, and an estimate of group size), plus a second estimate of group size provided by the second observer. We extend the model to situations in which detection of individuals within groups declines with distance. We simulated 12 data sets and used Bayesian methods to compare the performance of the new MRDS‐Nmix model to an MRDS model. Abundance estimates generated by the MRDS‐Nmix model exhibited minimal bias and nominal coverage levels. In contrast, MRDS abundance estimates were biased low and exhibited poor coverage. Many species of conservation interest reside in groups and could benefit from an estimator that better accounts for imperfect detection. Furthermore, the ability to relax the assumption of perfect detection of individuals within detected groups may allow surveyors to re‐allocate resources toward detection of new groups instead of extensive surveys of known groups. We believe the proposed estimator is feasible because the only additional field data required are a second estimate of group size.     

Molecular insights into the mechanisms of cation-type specific stability and denaturation of poly-l-glutamate: a simulation study

Cation-induced conformational changes of peptide as a guide to developing insights into human diseases-related proteins have received a lot of attention. The interactions between poly-l-glutamate (PGA) and different cations, including Na⁺, K⁺ and Mg²⁺, respectively, are studied in solvent at a concentration of 1 M, and the behaviours of peptide with different cations are investigated. For Na⁺, an oscillatory stabilising process to α-helix PGA is found, in accordance with the uniform free-energy landscape, whereas for K⁺, an extended α-helix structure is formed by the terminal turns, suggesting a weaker attraction to charged head groups. For Mg²⁺, the bridged charged side chains are responsible for the maximum probability of helix state. These distinct structural changes can be attributed to the different interactions between charged head groups and cations. Both Na⁺ and K⁺ are mainly attracted around head groups by direct ion binding while Mg²⁺ is centrally trapped among adjacent charged head groups. In addition, a surprising shift of the backbone hydrogen bond, from intact state to intermediate state, is observed. This is opposite to the stabilising effect of Na⁺ around negatively charged head groups.     

Perspectives to produce positively or negatively charged polyhydroxyalkanoic acids

An overview is provided on the possibilities of producing positively and negatively charged poly(β-hydroxyalkanoates), PHAs. A large variety of bacterial polyesters with functionalized terminal side chains can be produced in microbial fermentation processes by a direct polymerization of respective carbon sources, that is, carbon sources that carry functional groups in their ω-position. However, charged PHAs are not accessible by a direct approach and must be synthesized via polymer-analogous reactions of functionalized bacterial polyesters. PHA polyanions are produced by converting the terminal functional groups into carboxylate groups, while PHA polycations are produced by introducing terminal amino groups. PHAs with terminal vinyl groups emerged as most suitable PHA precursors, as they can be produced in relatively high yields and the double bonds are sufficiently reactive. The oxidation of vinyl groups yields PHA polyanions. The conversion of terminal vinyl groups into epoxides with a subsequent ring-opening reaction with an amine yields PHA polycations. Other functionalized PHA that potentially lend themselves to polymer-analogous reactions are reviewed.     

Strategy for the synthesis of large peptides: An application to the total synthesis of human parathyroid hormone [hPTH(1–84)]

A strategy suitable for the synthesis of larger peptides is proposed. It involves the following four considerations: (1) all of the side-chain functional groups are protected by benzyl-type protective groups; (2) a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide, is used for the fragment-condensation reactions together with 1-hydroxybenzotriazole as the additive; (3) all the protective groups are cleaved simultaneously by the HF method in the final stage of the synthesis; and (4) side products formed are detected and removed by an efficient high-performance liquid chromatography procedure. The usefulness of these procedures is demonstrated taking the synthesis of human parathyroid hormone [hPTH(1–84)] as an example.     

Reaction of ovine interstitial cell stimulating hormone with citraeonic and maleic anhydrides

The free amino groups of ovine interstitial cell stimulating hormone and its subunits are modified with citraconic and maleic anhydrides. Three lysine residues in the native hormone are not available for reaction. Introduction of negatively charged groups does not cause dissociation of the hormone into its subunits. The completely modified interstitial cell stimulating hormone-β combines with the native α subunit to give a recombinant that has biological activity, while the modified interstitial cell stimulating hormone-α is unable to form an active product with native interstitial cell stimulating hormone-β. The results suggest that the ?-NH₂ groups of the α subunit play an important role in determining biological activity.     

Cross-Cultural aspects of bereavement. II: Ethnic and cultural variations in the development of bereavement practices

Despite a growing interest in bereavement in cross-cultural perspective, few reports have described a comparative analysis of bereavement. By examining the social contexts in the transformations of Western bereavement practices, structures common to bereavement in a range of cultures can be identified. The paper compares the contemporary bereavement practices of several ethnic and cultural groups in North America: Blacks; ethnic Chinese; Southeast Asian refugees; Haitians; Italians; Greeks; and Spanish-speaking groups. Consideration is given to the state of widowhood in different cultural systems. The impact of modernization among traditional societies demonstrates that even though Western technologies are incorporated into the procedures followed by these modernizing societies, the deep cultural code remains intact. Five questions require further clarification: is bereavement an illness, or a rite de passage and a normal life event? How widespread and useful are protective factors, such as group support, that facilitate successful resolution of grief? How effective are mourning practices of various ethnic groups in preventing “bad grief”, and might some of these practices be beneficial if taken up by other ethnic groups? How can the Western health practitioner know that a bereaved person from an unfamiliar cultural group is suffering “bad grief”? How acceptable is Western grief counseling to non-Western clients?     

Between-clutch interactions affect a benefit of group feeding for pipevine swallowtail larvae

Abstract.  1. In California, early instar larvae of the pipevine swallowtail ( Battus philenor ) develop at an accelerated rate when feeding in large groups compared with small groups due to a plant-mediated response to feeding group size. Larvae benefit from accelerated growth because the time larvae remain in early stages, where mortality is highest, is reduced. Occasionally, multiple clutches are laid on the same plant stem. Clutch size modification by females ovipositing on plant with previously laid clutches and the effect of kinship and group size on larval behaviour was examined. The direct and indirect interactions between clutches were investigated to determine if group size and time between clutch establishment affects the performance of early instar larvae.
2. Larger groups consume the young foliage more quickly and develop at an accelerated rate compared with smaller groups. Older foliage available to later clutches is an inferior food resource compared with younger foliage.
3. There was no evidence that females adjust clutch size in response to the presence of conspecific clutches.
4. Second groups of larvae readily joined previously established feeding groups. There were no observed behavioural differences between sibling and mixed-family groups.
5. The effect of a second group on the growth of the initial group was dependent on the size of both groups and the time interval between the arrival of the two groups.
6. Accelerated growth associated with larger feeding aggregations was absent when these groups were introduced to plants with previously established groups.
7. It is beneficial for ovipositing females to avoid plants with previously laid clutches because direct and indirect interactions with established clutches compromises larval performance.     

Revision of Chaetodipus arenarius (Rodentia: Heteromyidae)

Chaetodipus arenarius is an endemic species of the Baja California Peninsula. It has undergone taxonomic changes in the last few years. Today, two species, C. arenarius and Chaetodipus dalquesti, are formally recognized with an unknown range for each. However, genetic analysis showed the possible presence of a third species. The objectives of this study were to use molecular data (cytochrome b and cytochrome c oxidase subunit III genes) to determine how many genetic groups are present in C. arenarius in the Baja California Peninsula; if these groups have morphological characteristics that could be used to distinguish them; if the genetic groups have limited distributions; identify taxonomic implications; and establish if there are any associations amongst genetic groups and different habitats. Bayesian inference, maximum parsimony, maximum likelihood, distance optimality criteria, and minimum spanning network indicated three monophyletic groups with high genetic differences (5.54–13.59%). These groups are morphologically diagnosable based on pelage and morphometric characters and geographical range. The three genetic groups correspond to three taxa previously described as subspecies or species. Based on our results, these should be considered to be different species: C. arenarius occupies the most extreme habitats with hot summers; C. dalquesti occupies the moistest coastal areas in the southern part of the peninsula, and Chaetodipus siccus is restricted by mountain ranges to the isolated Los Planes Basin and Cerralvo Island. © 2010 The Linnean Society of London, Zoological Journal of the Linnean Society, 2010.     

Formal taxa, species groups, and perception of the genus Diplodactylus (Reptilia: Gekkonidae)

Genera with large numbers of species present particular difficulties; the analysis of relationships, of included taxa may be roblematic. One attempt to aproach this problem involves the reco of clusters of species tIat may be informally assembgd into species groups. The problems tE:g the recognition of such assemblages may induce are exlored. It is not that the species groups, as originail formulated, are problematic as they are initiafy erected to demarcate clusters withm an imperfectly known phylogeny of a supposedly monophyletic group. These species groups, however, tend to become recognized as “taxa” rather than operationaf clusters and as such tend to influence the approach to the inclusive taxon taken by subsequent workers. Rather than testing the concept of the species grous, there is a tendency to retain them and to insert other groups between them that do not exactly fit the original scheme. The establishment of species groups, first used to clarify a complex situation, has teen a source of problems for subseuent workers. The history of this aproach is traced for the gekkonid genus Diplodactylus and the problems that have arisen are outlined.     

The Evolution of Different Forms of Sociality: Behavioral Mechanisms and Eco-Evolutionary Feedback

Different forms of sociality have evolved via unique evolutionary trajectories. However, it remains unknown to what extent trajectories of social evolution depend on the specific characteristics of different species. Our approach to studying such trajectories is to use evolutionary case-studies, so that we can investigate how grouping co-evolves with a multitude of individual characteristics. Here we focus on anti-predator vigilance and foraging. We use an individual-based model, where behavioral mechanisms are specified, and costs and benefits are not predefined. We show that evolutionary changes in grouping alter selection pressures on vigilance, and vice versa. This eco-evolutionary feedback generates an evolutionary progression from “leader-follower” societies to “fission-fusion” societies, where cooperative vigilance in groups is maintained via a balance between within- and between-group selection. Group-level selection is generated from an assortment that arises spontaneously when vigilant and non-vigilant foragers have different grouping tendencies. The evolutionary maintenance of small groups, and cooperative vigilance in those groups, is therefore achieved simultaneously. The evolutionary phases, and the transitions between them, depend strongly on behavioral mechanisms. Thus, integrating behavioral mechanisms and eco-evolutionary feedback is critical for understanding what kinds of intermediate stages are involved during the evolution of particular forms of sociality.     

Genetic Heterogeneity in Wild Isolates of Cellular Slime Mold Social Groups

This study addresses the issues of spatial distribution, dispersal, and genetic heterogeneity in social groups of the cellular slime molds (CSMs). The CSMs are soil amoebae with an unusual life cycle that consists of alternating solitary and social phases. Because the social phase involves division of labor with what appears to be an extreme form of “altruism”, the CSMs raise interesting evolutionary questions regarding the origin and maintenance of sociality. Knowledge of the genetic structure of social groups in the wild is necessary for answering these questions. We confirm that CSMs are widespread in undisturbed forest soil from South India. They are dispersed over long distances via the dung of a variety of large mammals. Consistent with this mode of dispersal, most social groups in the two species examined for detailed study, Dictyostelium giganteum and Dictyostelium purpureum, are multi-clonal.     

Sialic acid, electrophoretic mobility and transmembrane potentials of the Amphiuma red cell

Red cells from the giant salamander Amphiuma means are shown to contain sialic acid. The amount removed by the action of neuraminidase is equal to that released by acid hydrolysis, indicating that all of the sialic acid is present on the outer surface of the plasma membrane. These cells have a negative electrophoretic mobility and 100% enzymatic removal of sialic acid results in a 40% reduction in the mobility, suggesting that either a fraction of the sialic acid carboxyl groups are unavailable to the action of external electric fields, or other negatively charged groups contribute to the surface charge. A further reduction in mobility of normal and sialic acid-free cells is caused by an increased extracellular calcium concentration. The negative groups affected by calcium are most likely to be phosphate groups, since the isoelectric point of the cells is found to lie between the pK values for H₂PO₄⁻ groups and the carboxyl groups of sialic acid. Membrane potentials of single cells, from which 80% or more of the total sialic acid had been removed, were identical to those measured in normal cells, confirming that sialic acid plays little, if any, direct role in the maintenance of membrane potentials and ionic permeabilities.     

Multiaberrant cells in groups of people exposed to radiation in different situations and their possible biological role

The results of the analysis of multiaberrant cells (MAC) obtained in the course of long-term investigation of cytogenetic effects in human peripheral blood lymphocytes are presented. MAC were discovered in different groups of people exposed to the radiation factor. No such cells were found in control groups. The greatest number of MAC “carriers” (37.5%) was registered among employees of radiochemical plants who had contacts with plutonium salts. The highest frequency of MAC (2.49 ± 0.59 per 1000 cells) was also revealed in the same group. It exceeded by an order of magnitude the values in other examined groups. In the groups of radiochemical workers, cosmonauts, and miners from Tselinograd the frequency of dicentrics and centric rings was also the highest as compared to that in other groups. The character of chromosome aberrations observed in MAC suggests that they are formed under the action of the radiation factor, and their frequency among different groups of people exposed to radiation makes it possible to assume that formation of MAC is a result of the action on lymphocytes of α-particles emitted by radionuclides incorporated in the organism. Classical MAC observed in routine studies (fluorescence plus Giemsa staining) are only an extreme manifestation of cell damage. To elucidate the true picture of chromosome rearrangements induced by radiation and the role of MAC in the tumor process, it is necessary to use the methodical potentialities of modern molecular cytogenetics, including the FISH method.     

Regulatory mechanisms of cellular respiration; the role of soluble sulfhydryl groups as shown by the effect of sulfhydryl reagents on the respiration of sea urchin sperm

Oxidizing agents of sulfhydryl groups such as iodosobenzoate, alkylating agents such as iodoacetamide, and mercaptide-forming agents such as cadmium chloride, mercuric chloride, p-chloromercuribenzoate, sodium arsenite, and p-carboxyphenylarsine oxide, added in small concentrations to a suspension of sea urchin sperm produced an increase in respiration. When the concentration was increased there was an inhibition. These effects are explained by postulating the presence in the cells of two kinds of sulfhydryl groups: soluble sulfhydryl groups, which regulate cellular respiration, and fixed sulfhydryl groups, present in the protein moiety of enzymes. Small concentrations of sulfhydryl reagents combine only with the first, thus producing an increase in respiration; when the concentration is increased, the fixed sulfhydryl groups are also attacked and inhibition of respiration is the consequence. Other inhibitors of cell respiration, such as cyanide and urethanes, which do not combine with -SH groups, did not stimulate respiration in small concentration.     

The precursor strategy: terminus methoxyoxalamido modifiers for single and multiple functionalization of oligodeoxyribonucleotides

Synthesis of new terminus modifiers, bearing, along with a phosphoramidite moiety, one, two or four methoxyoxalamido (MOX) precursor groups, is described. These modifiers are introduced onto the 5′-end of a synthetic oligodeoxyribonucleotide as the last step of an automated synthesis to form the MOX precursor oligonucleotide. The MOX groups are then post-synthetically derivatized with an appropriate primary amine to construct a 5′-modified oligonucleotide. The efficiency and simplicity of the novel modifying strategy were demonstrated in the synthesis of a number of 5′-functionalized oligonucleotides.     

Infrared investigation of poly-L-histidine structure dependent on protonation

Poly-L -histidine (PLH) films at different degrees of protonation were produced mid subjected to infrared spectroscopic investigation (range 4000-650 cm^?1). In addition, the N-deuterated film spectra were plotted. The amide II and III bands show that the peptide group is present in the trans form. The amide I and II bands show that at 0% and 50% protonation the PLH occurs as an α-helix and at 100% protonation as a random coil with some ranges in β structure. At 0% and 50% protonation, no hydration water is bound to the backbone. At 0% protonation all NH groups are linked to each other or to water molecules via hydrogen bonds. At 50% protonation NH⁺?N bonds form between the imidazole rings. These protons are present in continuous energy level distribution. Such bonds with tunneling protons are extremely polarizable and between these bonds may act proton dispersion forces. The Cl^? ions are bonded to the NH groups of the imidazole groups. The hydration water is bonded to the Cl^?? ions and to the NH groups. At 100% protonation, hydration water is bonded also to the CO groups of the backbone. The NH groups of the backbone, like those of the rings, endeavor especially in the dry state to bond to the Cl^? ions. This leads to a strong steric constraint of the random coil.     

Alkylthiolation. Evidence for involvement in cell division

Several malignant hematopoietic cells from mice, previously shown to require sulfhydryl compounds and serum for proliferation $\text{in vitro}$, are shown to grow well in medium lacking both of these components if methylthio compounds are provided at appropriate concentrations. The methylthio groups can be provided as the mixed disulfides of methyl mercaptan and various thiols. The optimal concentration of the various disulfides is between 1×10^?5 and 1×10^?4 M. The cells can be maintained indefinitely in serum-free medium containing cysteine-methyl disulfide and one of several purified proteins. The evidence is consistent with the theory that these cells require an exogenous source of alkylthio groups for division, that serum is a source of these groups, and that sulfhydryl compounds act as carriers to transport the groups into the cells. A new diffusion analysis is described for quantitative measurement of disulfides of volatile mercaptans.     

From Schooling to Shoaling: Patterns of Collective Motion in Zebrafish (Danio rerio)

Animal groups on the move can take different configurations. For example, groups of fish can either be ‘shoals’ or ‘schools’: shoals are simply aggregations of individuals; schools are shoals exhibiting polarized, synchronized motion. Here we demonstrate that polarization distributions of groups of zebrafish (Danio rerio) are bimodal, showing two distinct modes of collective motion corresponding to the definitions of shoaling and schooling. Other features of the group''s motion also vary consistently between the two modes: zebrafish schools are faster and less dense than zebrafish shoals. Habituation to an environment can also alter the proportion of time zebrafish groups spend schooling or shoaling. Models of collective motion suggest that the degree and stability of group polarization increases with the group''s density. Examining zebrafish groups of different sizes from 5 to 50, we show that larger groups are less polarized than smaller groups. Decreased fearfulness in larger groups may function similarly to habituation, causing them to spend more time shoaling than schooling, contrary to most models'' predictions.     

Automated identification of social interaction criteria in Drosophila melanogaster

The study of social behaviour within groups has relied on fixed definitions of an ‘interaction’. Criteria used in these definitions often involve a subjectively defined cut-off value for proximity, orientation and time (e.g. courtship, aggression and social interaction networks) and the same numerical values for these criteria are applied to all of the treatment groups within an experiment. One universal definition of an interaction could misidentify interactions within groups that differ in life histories, study treatments and/or genetic mutations. Here, we present an automated method for determining the values of interaction criteria using a pre-defined rule set rather than pre-defined values. We use this approach and show changing social behaviours in different manipulations of Drosophila melanogaster. We also show that chemosensory cues are an important modality of social spacing and interaction. This method will allow a more robust analysis of the properties of interacting groups, while helping us understand how specific groups regulate their social interaction space.     

Chemical modification of horseradish peroxidase. Preparation and characterization of tracer enzymes with different isoelectric points.

Horseradish peroxidase (HRP), a plant glycoprotein with a molecular weight of 40,000 D and a molecular radius (ae) of 30 A, has been modified chemically to prepare tracer molecules with different molecular charge. Modification of free carboxyl groups on the enzyme is achieved by carbodiimide activation and subsequent reaction of activated carboxyl groups with a nucleophile; uncharged groups or radicals containing additional positively charged moieties are introduced into the protein molecule resulting in an increased net positive charge of the tracer. Amino groups in the protein molecule are modified by acetylation or succinylation; this reaction will increase the net negative charge of the enzyme by either introducing an uncharged group or an additional carboxyl radical. The tracer molecules so obtained are then characterized in terms of molecular size and charge by column chromatography and isoelectric focusing respectively. The enzymatic activity as measured by 3,3'-diaminobenzidine reaction, the pH optimum and the absorption spectra for the modified enzymes remain virtually unchanged.