Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Nature’s nations: the shared conservation history of Canada and the USA

Historians often study the history of conservation within the confines of national borders, concentrating on the bureaucratic and political manifestations of policy within individual governments. Even studies of the popular expression of conservationist ideas are generally limited to the national or sub-national (province, state, etc.) scale. This paper suggests that conservationist discourse, policy and practice in Canada and the USA were the products of a significant cross-border movement of ideas and initiatives derived from common European sources. In addition, the historical development of common approaches to conservation in North America suggests, contrary to common assumptions, that Canada did not always lag behind the USA in terms of policy innovation. The basic tenets of conservation (i.e. state control over resource, class-based disdain for subsistence hunters and utilitarian approaches to resource management) have instead developed at similar time periods and along parallel ideological paths in Canada and the USA

The umbilical vein in the human fetus has a non‐linear growth pattern across gestation

Introduction and Objectives Estimation of the umbilical venous blood flow volume relies on the diameter of the vein, which has been reported to be reduced in severely growth restricted fetuses. However, there is only limited information on the growth pattern of this vessel in the normal human fetus. The aim of this study is to examine the growth pattern of the umbilical vein across gestation in low-risk human pregnancies. Methods In a prospective, longitudinal ultrasound study of 136 low-risk pregnancies, the internal diameter of the intra-amniotic portion of the umbilical vein was measured at 18, 26 and 34 weeks of gestation. To investigate the growth pattern of the venous diameter, the ratios of diameters at 26 weeks to diameters at 18 weeks (ratio 1) and the ratios at 34 to 26 weeks (ratio 2) were also calculated. A paired-sample t-test was performed to compare the means of the two ratios. Results The mean diameter of the umbilical vein at 18 weeks was 2.8 mm (SD 0.40), 5.8 mm (SD 0.67) at 26 weeks and 7.6 mm (SD 0.98) at 34 weeks. The mean of ratio 1 was 2.06 (95% CI 2.01–2.14), which was significantly higher than ratio 2 (mean 1.33, 95% CI 1.29–1.36), P < 0.001. Conclusion The umbilical venous diameter demonstrates a non-linear growth pattern between 18 and 34 weeks of gestation. The diameter doubled in size between 18 and 26 weeks but grew at a slower rate between 26 and 34 weeks of gestation. This study provides new data on the normal growth pattern of the umbilical vein by identifying a period of gestation where its growth is accelerated