Implication of the visual system in the regulation of activity cycles in the absence of solar light: 2-[125I]iodomelatonin binding sites and melatonin receptor gene expression in the brains of demersal deep-sea gadiform fish

Relative eye size, gross brain morphology and central localization of 2-[¹²⁵I]iodomelatonin binding sites and melatonin receptor gene expression were compared in six gadiform fish living at different depths in the north-east Atlantic Ocean: Phycis blennoides (capture depth range 265 to 1260 m), Nezumia aequalis (445 to 1512 m), Coryphaenoides rupestris (706 to 1932 m), Trachyrincus murrayi (1010 to 1884 m), Coryphaenoides guentheri (1030 m) and Coryphaenoides (Nematonurus) armatus (2172 to 4787 m). Amongst these, the eye size range was 0.15 to 0.35 of head length with a value of 0.19 for C. (N.) armatus, the deepest species. Brain morphology reflected behavioural differences with well-developed olfactory regions in P. blennoides, T. murrayi and C. (N.) armatus and evidence of olfactory deficit in N. aequalis, C. rupestris and C. guentheri. All species had a clearly defined optic tectum with 2-[¹²⁵I]iodomelatonin binding and melatonin receptor gene expression localized to specific brain regions in a similar pattern to that found in shallow-water fish. Melatonin receptors were found throughout the visual structures of the brains of all species. Despite living beyond the depth of penetration of solar light these fish have retained central features associated with the coupling of cycles of growth, behaviour and reproduction to the diel light–dark cycle. How this functions in the deep sea remains enigmatic.     

Why most of the Timiriaseviinae (Ostracoda,Crustacea) became extinct

Mesozoic and Cenozoic species of Timiriaseviinae, like the recent species have ecological and biological properties defining them as k-strategists. The extinction of most of them could be due to the contraction of their niche during the Cyprididae explosion in the Upper Jurassic-Lower Cretaceous. Their narrow ecological tolerance limits and poor dispersion abilities made them very vulnerable during major environmental disturbances. Their low rate of speciation during the Tertiary and Quaternary in Europe did not allow to start a new cycle of diversification. This could be due to the change of the reproductive pattern from bisexual to parthenogenetic.     

R-2-hydroxyglutarate attenuates aerobic glycolysis in leukemia by targeting the FTO/m6A/PFKP/LDHB axis

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Shark depredation in commercial and recreational fisheries

Shark depredation, where a shark partially or completely consumes an animal caught by fishing gear before it can be retrieved to the fishing vessel, occurs in commercial and recreational fisheries worldwide, causing a range of negative biological and economic impacts. Despite this, it remains relatively understudied compared to other fisheries issues. This is the first review of the literature relating to shark depredation, which also includes an overview of the potential mechanisms underlying its occurrence and options for mitigation. Furthermore, this review highlights key research gaps that remain to be investigated, thereby providing impetus for future research. In total, 61 studies have been published between 1955 and 2018, which include information on shark depredation. These studies recorded quantitative rates of depredation between 0.9 and 26% in commercial and recreational fisheries and during research fishing, identified 27 shark species from seven families that were responsible for depredation and discussed potential factors influencing its occurrence. Information from research into bycatch mitigation and the testing of shark deterrent approaches and technologies is also presented, in the context of applying these approaches to the reduction of shark depredation. This review presents an holistic overview of shark depredation in fisheries globally and, in doing so, provides a central resource for fisheries researchers and managers focusing on this topic to stimulate further collaborative research on this important fisheries issue.     

Aggregating fields of annual crops to form larger-scale monocultures can suppress dispersal-limited herbivores

An important part of landscape ecology is determining how the arrangement (aggregation or fragmentation) of patches in space influences the population dynamics of foraging organisms. One hypothesis in agricultural ecology is that fine-grain spatial heterogeneity in cropping (many small agricultural fields) should provide better pest control than coarse-grain heterogeneity (few large agricultural fields); this hypothesis has been proposed as an explanation for the increased pest abundance associated with agricultural intensification. However, empirical studies have found mixed support for this hypothesis, and some, surprisingly, demonstrate a strong decrease in pest abundance with increased crop aggregation. We developed a spatially explicit simulation model of pest movement across an agricultural landscape to uncover basic processes that could reduce pest abundance in landscapes with fewer, larger fields. This model focuses on herbivore movement and does not include predation effects or other biological interactions. We found that field aggregation in the model led to severely reduced pest densities and further discovered that this relationship was due to an increased distance between fields and a decreased “target area” in more aggregated landscapes. The features that create a negative relationship between aggregation and pest densities rely on crop rotation and limited dispersal capabilities of the pests. These findings help to explain seemingly counter-intuitive empirical studies and provide an expectation for when field aggregation may reduce pest populations in agro-ecosystems.     

Identification and expression of the first nonmammalian amyloid-beta precursor-like protein APLP2 in the amphibian Xenopus laevis.

The Alzheimer's disease-linked amyloid-beta precursor protein (APP) belongs to a superfamily of proteins, which also comprises the amyloid-beta precursor-like proteins, APLP1 and APLP2. Whereas APP has been identified in both lower and higher vertebrates, thus far, APLP1 and 2 have been characterized only in human and rodents. Here we identify the first nonmammalian APLP2 protein in the South African claw-toed frog Xenopus laevis. The identity between the Xenopus and mammalian APLP2 proteins is approximately 75%, with the highest degree of conservation in a number of amino-terminal regions, the transmembrane domain and the cytoplasmic tail. Furthermore, amino acid residues known to be phosphorylated and glycosylated in mammalian APLP2 are conserved in Xenopus. The availability of the Xenopus APLP2 protein sequence allowed a phylogenetic analysis of APP superfamily members that suggested the occurrence of APP and preAPLP lineages with their separation predating the mammalian-amphibian split. As in mammals, Xenopus APLP2 mRNA was ubiquitously expressed and alternatively spliced forms were detected. However, the expression ratios between the mRNA forms in the various tissues examined were different between Xenopus and mammals, most prominently for the alternatively spliced forms containing the Kunitz protease inhibitor-coding region that were less abundantly expressed than the corresponding mammalian forms. Thus, the identification of APLP2 in Xenopus has revealed evolutionarily conserved regions that may help to delineate functionally important domains, and its overall high degree of conservation suggests an important role for this APP superfamily member.