Techniques for determining opal in deep-sea sediments: A comparison of radiolarian counts and x-ray diffraction data

Detailed records of two estimators of the biogenic silica content of deep-sea sediments, x-ray diffraction analysis opal concentrations and quantitative radiolarians per gram counts from microscope slides were compared in downcore sediments from northwest Pacific core RC14-105 to evaluate and to intercalibrate the two techniques. Both the degree to which the data were similar and the degree to which inferences from the data were similar were considered. Although both data sets are internally consistent and reflect surface water processes, they are not equivalent and there is no way to convert one linearly into the other. The numbers of radiolarians per gram of sediment appear to respond to the same factors which control the fluctuations in the radiolarian assemblage distrbutions in the area. The opal contents respond to the factors which control the total siliceous productivity of the area.     

Home range size estimates of red deer in Germany: environmental,individual and methodological correlates

Home range size (HRS) is the fundamental measure of space use by animals. Despite the importance of the home range concept, there is no consensus on how to estimate the HRS of animals. Assessments of the performance of commonly applied HRS estimators have largely been based on simulated data or on location data of few sample individuals occupying one study area. To empirically evaluate the impact of supplementary feeding, habitat composition, red deer sex, and estimation method (minimum convex polygon (MCP), kernel density estimator (KDE) and α-local convex hull (α-LoCoH)) on HRS, we analysed the data of 183 annual red deer home ranges using a mixed modelling approach. Red deer HRSs were smallest in areas with substantial supplementary feeding, intermediate in areas with closed forest cover but no supplementary feeding, and largest in fragmented landscapes where supplementary feeding rarely occurs. Consistently, male HRSs were larger than female HRSs. While MCP- and KDE-HRS estimates were roughly similar, estimates from the α-LoCoH method were substantially smaller than those of MCP and KDE. Analyses of 342 seasonal HRS largely reflected patterns of annual HRS. However, seasonal HRS differed between seasons and red deer sex. In areas with no or little feeding, red deer adjusted HRS seasonally, whereas red deer supplied with supplementary food during winter did not alter their HRS seasonally. Our study suggests that supplementary feeding and habitat configuration strongly affect the spatial ecology of red deer; this might have considerable sanitary and ecological implications. We suggest that sex differences in annual space use extent are proportional along a resource gradient but are mediated by seasons. Finally, method-related variation in space use studies of animals needs to be considered more cautiously.     

Plausible Emergence and Self Assembly of a Primitive Phospholipid from Reduced Phosphorus on the Primordial Earth

How life arose on the primitive Earth is one of the biggest questions in science. Biomolecular emergence scenarios have proliferated in the literature but accounting for the ubiquity of oxidized (+?5) phosphate (PO₄^3?) in extant biochemistries has been challenging due to the dearth of phosphate and molecular oxygen on the primordial Earth. A compelling body of work suggests that exogenous schreibersite ((Fe,Ni)₃P) was delivered to Earth via meteorite impacts during the Heavy Bombardment (ca. 4.1–3.8 Gya) and there converted to reduced P oxyanions (e.g., phosphite (HPO₃^2?) and hypophosphite (H₂PO₂^?)) and phosphonates. Inspired by this idea, we review the relevant literature to deduce a plausible reduced phospholipid analog of modern phosphatidylcholines that could have emerged in a primordial hydrothermal setting. A shallow alkaline lacustrine basin underlain by active hydrothermal fissures and meteoritic schreibersite-, clay-, and metal-enriched sediments is envisioned. The water column is laden with known and putative primordial hydrothermal reagents. Small system dimensions and thermal- and UV-driven evaporation further concentrate chemical precursors. We hypothesize that a reduced phospholipid arises from Fischer–Tropsch-type (FTT) production of a C8 alkanoic acid, which condenses with an organophosphinate (derived from schreibersite corrosion to hypophosphite with subsequent methylation/oxidation), to yield a reduced protophospholipid. This then condenses with an α-amino nitrile (derived from Strecker-type reactions) to form the polar head. Preliminary modeling results indicate that reduced phospholipids do not aggregate rapidly; however, single layer micelles are stable up to aggregates with approximately 100 molecules.