Proximate and ultimate causes of signal diversity in the electric fish Gymnotus

A complete understanding of animal signal evolution necessitates analyses of both the proximate (e. g. anatomical and physiological) mechanisms of signal generation and reception, and the ultimate (i.e. evolutionary) mechanisms underlying adaptation and diversification. Here we summarize the results of a synthetic study of electric diversity in the species-rich neotropical electric fish genus Gymnotus. Our study integrates two research directions. The first examines the proximate causes of diversity in the electric organ discharge (EOD) - which is the carrier of both the communication and electrolocation signal of electric fishes - via descriptions of the intrinsic properties of electrocytes, electrocyte innervation, electric organ anatomy and the neural coordination of the discharge (among other parameters). The second seeks to understand the ultimate causes of signal diversity -via a continent-wide survey of species diversity, species-level phylogenetic reconstructions and field-recorded head-to-tail EOD (ht-EOD) waveforms (a common procedure for characterizing the communication component of electric fish EODs). At the proximate level, a comparative morpho-functional survey of electric organ anatomy and the electromotive force pattern of the EOD for 11 species (representing most major clades) revealed four distinct groups of species, each corresponding to a discrete area of the phylogeny of the genus and to a distinct type of ht-EOD waveform. At the ultimate level, our analyses (which emphasize the ht-EOD) allowed us to conclude that selective forces from the abiotic environment have had minimal impact on the communication component of the EOD. In contrast, selective forces of a biotic nature - imposed by electroreceptive predators, reproductive interference from heterospecific congeners, and sexual selection - may be important sources of diversifying selection on Gymnotus signals

A simple, low-blank batch purification method for high-precision boron isotope analysis

This work was supported by NERC IAPETUS PhD Studentships NE/RO12253/1 to M.T., J.C.B. and E.L., an IAPETUS2 PhD Studentship NE/S007431/1 to C.X.; S.N. was supported by the MOST 111-2116M-002-032-MY3 Grant; J.W.B.R acknowledges support from NERC (Grant NE/N011716/1) and from the European Research Council under the European Union's Horizon 2020 research and innovation program (Grant agreement 805246).Boron (B) isotopes are widely used in the Earth sciences to trace processes ranging from slab recycling in the mantle to changes in ocean pH and atmospheric CO2. Boron isotope analysis is increasingly achieved by multi-collector inductively coupled plasma mass spectrometry, which requires separation of B from the sample matrix. Traditional column chromatography methods for this separation have a well-established track record but are time consuming and prone to contamination from airborne blank. Here, we present an extensive array of tests that establish a novel method for B purification using a batch method. We discuss the key controls and limitations on sample loading, matrix removal and B elution including sample volume, ionic strength, buffer to acid ratio and elution volume, all of which may also help optimize column-based methods. We find consistent, low procedural blanks of 10 ± 16 pg and excellent reproducibility: 10 ng NIST RM 8301 foram [8301f] yields 14.58 ± 0.11‰ 2SD n = 15; 2.5 ng 8301f yields 14.60 ± 0.19‰ 2SD, n = 31; and overall long term 2SD on n = 218 samples pooling different sample sizes yields 14.62 ± 0.21‰ 2SD. This method also offers significant advantages in throughput, allowing the processing of 24 samples in ∼5 hr. This boron batch method thus provides a fast, reproducible, low-blank method for purification of boron for high precision isotopic analyses.Peer reviewe

Technical note: No impact of alkenone extraction on foraminiferal stable isotope, trace element and boron isotope geochemistry

Recent advances in geochemical techniques mean that several robust proxies now exist to determine the past carbonate chemistry of the oceans. Foraminiferal δ11B and alkenone carbon isotopes allow us to reconstruct sea-surface pH and pCO2, respectively, and the ability to apply both proxies to the same sediment sample would give strongly paired datasets and reduce sample waste. However, no studies to date have examined whether the solvents and extraction techniques used to prepare alkenones for analysis also impact the geochemistry of foraminifera within those sediments. Here we examine six species pairs of planktic foraminifera, with half being taken from non-treated sediments and half being taken from sediments where alkenones have been extracted. We look for visual signs of contrasting preservation and compare analyses of δ18O, δ13C, δ11B and trace elements (Li, B, Na, Mn, Mg, Sr and U/Ca). We find no consistent geochemical offset between the treatments and excellent agreement in δ11B measurements between them. Our results show that boron isotope reconstructions of pH in foraminifera from alkenone-extracted sediments can be applied with confidence.</p

Governing Young People: coherence and contradiction in contemporary youth justice

This article explores the burgeoning literature on modes and layers of governance and applies it to the complex of contemporary youth justice reform. Globalized neo-liberal processes of responsibilization and risk management coupled with traditional neo-conservative authoritarian strategies have dominated the political landscape. However, they also have to work alongside or within ‘new’ conceptions of social inclusion, partnership, restoration and moralization. These apparently contradictory strategies open up the possibility of multiple localized translations rather than an often assumed dominance of a uniform ‘culture of control’. The ensuing hybridity also suggests that any coherence within contemporary youth justice relies on continual negotiations between opposing, yet overlapping, discursive practices

An Examination of the Relationship Between Holland's Vocational Scales and a Measure of Interpersonal Needs

Previous research has provided evidence of relationships between vocational interests and other psychological variables. Test scores from the VPI and FIRO-B for 699 white male job applicants were subjected to multiple regression analyses to determine if individual interest scales could be predicted by particular configurations of interpersonal need scales. It was hypothesized that Enterprising, Realistic, and Investigative interests would be predicted by Inclusion and Control needs and Social interests by Inclusion, Control, and Affection needs. To control for effects of sample size, a smaller sample (n = 125) was randomly drawn from the original data and subjected to identical analyses. Results indicated only partial support for some hypotheses and revealed little common variance between the two domains