Sophisticated particle-feeding in a large Early Cambrian crustacean

Most Cambrian arthropods employed simple feeding mechanisms requiring only low degrees of appendage differentiation. In contrast, post-Cambrian crustaceans exhibit a wide diversity of feeding specializations and possess a vast ecological repertoire. Crustaceans are evident in the Cambrian fossil record, but have hitherto been known exclusively from small individuals with limited appendage differentiation. Here we describe a sophisticated feeding apparatus from an Early Cambrian arthropod that had a body length of several centimetres. Details of the mouthparts resolve this taxon as a probable crown-group (pan)crustacean, while its feeding style, which allowed it to generate and handle fine food particles, significantly expands the known ecological capabilities of Cambrian arthropods. This Early Cambrian record predates the major expansions of large-bodied, particle-handling crustaceans by at least one hundred million years, emphasizing the importance of ecological context in driving adaptive radiations.     

Jovian-like aurorae on Saturn

Planetary aurorae are formed by energetic charged particles streaming along the planet's magnetic field lines into the upper atmosphere from the surrounding space environment. Earth's main auroral oval is formed through interactions with the solar wind, whereas that at Jupiter is formed through interactions with plasma from the moon Io inside its magnetic field (although other processes form aurorae at both planets). At Saturn, only the main auroral oval has previously been observed and there remains much debate over its origin. Here we report the discovery of a secondary oval at Saturn that is approximately 25 per cent as bright as the main oval, and we show this to be caused by interaction with the middle magnetosphere around the planet. This is a weak equivalent of Jupiter's main oval, its relative dimness being due to the lack of as large a source of ions as Jupiter's volcanic moon Io. This result suggests that differences seen in the auroral emissions from Saturn and Jupiter are due to scaling differences in the conditions at each of these two planets, whereas the underlying formation processes are the same.     

A single positively selected West Nile viral mutation confers increased virogenesis in American crows

West Nile virus (WNV), first recognized in North America in 1999, has been responsible for the largest arboviral epiornitic and epidemic of human encephalitis in recorded history. Despite the well-described epidemiological patterns of WNV in North America, the basis for the emergence of WNV-associated avian pathology, particularly in the American crow (AMCR) sentinel species, and the large scale of the North American epidemic and epiornitic is uncertain. We report here that the introduction of a T249P amino acid substitution in the NS3 helicase (found in North American WNV) in a low-virulence strain was sufficient to generate a phenotype highly virulent to AMCRs. Furthermore, comparative sequence analyses of full-length WNV genomes demonstrated that the same site (NS3-249) was subject to adaptive evolution. These phenotypic and evolutionary results provide compelling evidence for the positive selection of a mutation encoding increased viremia potential and virulence in the AMCR sentinel bird species.     

Mutations in the gene encoding the basal body protein RPGRIP1L, a nephrocystin-4 interactor, cause Joubert syndrome

Protein-protein interaction analyses have uncovered a ciliary and basal body protein network that, when disrupted, can result in nephronophthisis (NPHP), Leber congenital amaurosis, Senior-L?ken syndrome (SLSN) or Joubert syndrome (JBTS). However, details of the molecular mechanisms underlying these disorders remain poorly understood. RPGRIP1-like protein (RPGRIP1L) is a homolog of RPGRIP1 (RPGR-interacting protein 1), a ciliary protein defective in Leber congenital amaurosis. We show that RPGRIP1L interacts with nephrocystin-4 and that mutations in the gene encoding nephrocystin-4 (NPHP4) that are known to cause SLSN disrupt this interaction. RPGRIP1L is ubiquitously expressed, and its protein product localizes to basal bodies. Therefore, we analyzed RPGRIP1L as a candidate gene for JBTS and identified loss-of-function mutations in three families with typical JBTS, including the characteristic mid-hindbrain malformation. This work identifies RPGRIP1L as a gene responsible for JBTS and establishes a central role for cilia and basal bodies in the pathophysiology of this disorder.     

Mutations in TTBK2, encoding a kinase implicated in tau phosphorylation, segregate with spinocerebellar ataxia type 11

The microtubule-associated protein tau (encoded by MAPT) and several tau kinases have been implicated in neurodegeneration, but only MAPT has a proven role in disease. We identified mutations in the gene encoding tau tubulin kinase 2 (TTBK2) as the cause of spinocerebellar ataxia type 11. Affected brain tissue showed substantial cerebellar degeneration and tau deposition. These data suggest that TTBK2 is important in the tau cascade and in spinocerebellar degeneration.     

Morphology and composition of the internal axis in two morphologically contrasting deep-water sea pens (Cnidaria: Octocorallia)

Umbellula encrinus Linnaeus, 1758 and Anthoptilum grandiflorum (Verrill, 1879) are two species of deep-water sea pens (Cnidaria: Octocorallia) commonly found in the Northwest Atlantic. These sea pens are frequently caught as fishing bycatch, but little is known about their biology. Here we characterise the internal skeleton (axis) of these two morphologically contrasting species, in terms of axis carbonate composition and proportion, morphology and metrics (i.e. cross-sectional area and weight) through gradients along their lengths. Using the conspicuous growth rings present in the axis of U. encrinus we also estimated intra-colonial variation in radial growth rates for this species. X-ray diffraction (XRD) analyses revealed that the carbonate portion of the axis is composed of magnesian calcite (Ca, Mg)CO₃ in both species. On average, the axis is composed of 71% carbonate material in U. encrinus, and 65% carbonate in A. grandiflorum. The carbonate proportion was greatly reduced from base (71%) to tip (33%) in the axis of U. encrinus, while in A. grandiflorum changes were less abrupt (~6% difference from base to tip). In U. encrinus, the axis is quadrangular in shape through its whole length, twisting longitudinally. Twisting can occur in both clockwise and anti-clockwise directions. The axis of A. grandiflorum varied from elliptical near the base to cylindrical through most of the remaining length, with no twisting observed. Axes’ cross-sectional areas also decreased with distance from the base in both species, being the largest near the base. Estimated radial growth rates in U. encrinus were variable within a single colony, ranging between 0.04 and 0.08 mm.yr^?1. This is the first study to describe changes along the axes of sea pens, and to characterise the axes in the studied species. It provides a baseline for studies considering sea pens’ skeletons (e.g. ocean acidification and palaeoceanography).     

Estimating private information usage amongst analysts: evidence from UK earnings forecasts

This paper introduces a methodology for estimating the likelihood of private information usage amongst earnings analysts. This is achieved by assuming that one group of analysts generate forecasts based on the underlying dynamics of earnings, while all other analysts are assumed to issue forecasts based on the prevailing consensus forecast. Given this behavioural dichotomy, we are able to derive (and estimate) a structural econometric model of forecast behaviour, which has implications regarding the determinants of analysts' private information endowments and forecast accuracy over the forecast horizon. Copyright © 2010 John Wiley & Sons, Ltd.     

Forecast accuracy and effort: The case of US inflation rates

This paper investigates the relationship between forecast accuracy and effort, where effort is defined as the number of times the model used to generate forecasts is recursively estimated over the full sample period. More specifically, within a framework of costly effort, optimal effort strategies are derived under the assumption that the dynamics of the variable of interest follow an autoregressive‐type process. Results indicate that the strategies are fairly robust over a wide range of linear and nonlinear processes (including structural break processes), and deliver forecasts of transitory, core and total inflation that require less effort to generate and are as accurate as (that is, are insignificantly different from) those produced with maximum effort. Copyright © 2010 John Wiley & Sons, Ltd.