Stress responses of the sea cucumber Holothuria forskali during aquaculture handling and transportation

Animal welfare during handling and transportation to aquaculture facilities or public aquaria is commonly estimated by addressing injury and mortality levels. Although these procedures have been optimized for different species, data on individual species’ cellular capabilities to tolerate stress are still scarce. In the present study, several biomarkers related with oxidative stress and energy metabolism were assessed in Holothuria forskali during animal acclimation, pre-transport, transport and quarantine. Combined analyses confirmed that sea cucumbers experienced high oxidative stress during transport, but had the capability to deal with it using a complex of cellular defence mechanisms, which enabled recovery from oxidative stress without permanent damage. Through a better understanding of individual species and the development of optimal parameters, this approach has the potential to improve animal wellbeing during and after acclimation, transportation and recovery processes.     

mangal – making ecological network analysis simple

The study of ecological networks is severely limited by 1) the difficulty to access data, 2) the lack of a standardized way to link meta‐data with interactions, and 3) the disparity of formats in which ecological networks themselves are stored and represented. To overcome these limitations, we have designed a data specification for ecological networks. We implemented a database respecting this standard, and released an R package (rmangal) allowing users to programmatically access, curate, and deposit data on ecological interactions. In this article, we show how these tools, in conjunction with other frameworks for the programmatic manipulation of open ecological data, streamlines the analysis process and improves replicability and reproducibility of ecological network studies.     

The role of pigment based plumage traits in resolving conflicts

The role of melanin ‘badges of status’, in male–male competition has been well‐studied, in contrast, carotenoid based plumage has largely been examined in the context of female mate choice. Recent work has shown that carotenoid signals can also function in male–male competition, although the functions of the two types of signals is currently unclear. Here, we examine the relationships between colouration, dominance and aggression in the crimson finch Neochmia phaeton, a species where males have both conspicuous red carotenoid plumage and a black melanin patch. We examined the importance of carotenoid and melanin based signals in three contexts: 1) among free‐living birds interacting at a feeding station: we found that neither colour signal influenced the outcome of interactions; 2) in staged dyadic contest in captivity: we found that coloration from carotenoid pigments was positively related to the probability of winning a contest, while the size of the melanin plumage patch was not related to winning; and 3) in staged dyadic contests where male plumage colour had been masked: we found that the number of interactions required to determine dominance increased. While the underlying natural plumage colour was still important in these contests, birds with more intense carotenoid colouration were now more likely to lose. These results confirm carotenoid‐based signalling in male–male contests. However this signal is used in conjunction with other factors such as self‐assessment and body condition. Contrary to traditional expectations, the black melanin patch was not found to be important in this context.     

Genetic and paleomodelling evidence of the population expansion of the cattle egret Bubulcus ibis in Africa during the climatic oscillations of the Late Pleistocene

Increasing aridity during glacial periods produced the retraction of forests and the expansion of arid and semi‐arid environments in Africa, with consequences for birds. Cattle egret Bubulcus ibis is a dispersive species that prefers semi‐arid environments and requires proximity to bodies of water. We expected that climatic oscillations led to the expansion of the range of the cattle egret during arid periods, such as the Last Maximum Glacial (LGM) and contraction of distribution during the Last Interglacial (LIG) period, resulting in contact of populations previously isolated. We investigated this hypothesis by evaluating the genetic structure and population history of 15 cattle egret breeding colonies located in west and South Africa using the mitochondrial DNA (mtDNA) control region, mtDNA ATPase 8 and 6, and an intron of nuclear gene transforming growth factor‐beta 2. Occurrence data and bioclimatic information were used to generate ecological niche models of three periods (present, LGM and LIG). We used the genetic and paleomodelling data to assess the responses of the cattle egret from Africa to the climatic oscillations during the late Pleistocene. Genetic data revealed low levels of genetic differentiation, signs of isolation‐by‐distance, as well as recent increases in effective population size that started during the LGM. The observed low genetic structure may be explained by recent colonization events due to the demographic expansion following the last glacial period and by dispersal capacity of this species. The paleomodels corroborated the expansion during the LGM, and a more restricted potential distribution during the LIG. Our findinds supports the hypothesis that the species range of the cattle egret expanded during arid periods and contracted during wet periods.     

Selenium and mercury levels in rat liver slices co-treated with diphenyl diselenide and methylmercury

Organoseleno-compounds have been investigated for its beneficial effects against methylmercury toxicity. In this way, diphenyl diselenide (PhSe)₂ was demonstrated to decrease Hg accumulation in mice, protect against MeHg-induced mitochondrial dysfunction, and protect against the overall toxicity of this metal. In the present study we aimed to investigate if co-treatment with (PhSe)₂ and MeHg could decrease accumulation of Hg in liver slices of rats. Rat liver slices were co-treated with (PhSe)₂ (0.5; 5 µM) and/or MeHg (25 µM) for 30 min at 37 °C and Se and Hg levels were measured by inductively coupled plasma mass spectrometry (ICP-MS) in the slices homogenate, P1 fraction, mitochondria and incubation medium. Co-treatment with (PhSe)₂ and MeHg did not significantly alter Se levels in any of the samples when compared with compounds alone. In addition, co-treatment with (PhSe)₂ and MeHg did not decrease Hg levels in any of the samples tested, although, co-incubation significantly increased Hg levels in homogenate. We suggest here that (PhSe)₂ could exert its previously demonstrated protective effects not by reducing MeHg levels, but forming a complex with MeHg avoiding it to bind to critical molecules in cell.