Developmental expression of transcription factor genes in a demosponge: insights into the origin of metazoan multicellularity

Demosponges are considered part of the most basal evolutionary lineage in the animal kingdom. Although the sponge body plan fundamentally differs from that of other metazoans, their development includes many of the hallmarks of bilaterian and eumetazoan embryogenesis, namely fertilization followed by a period of cell division yielding distinct cell populations, which through a gastrulation-like process become allocated into different cell layers and patterned within these layers. These observations suggest that the last common ancestor (LCA) to all living animals was developmentally more sophisticated than is widely appreciated and used asymmetric cell division and morphogen gradients to establish localized populations of specified cells within the embryo. Here we demonstrate that members of a range of transcription factor gene classes, many of which appear to be metazoan-specific, are expressed during the development of the demosponge Reniera, including ANTP, Pax, POU, LIM-HD, Sox, nuclear receptor, Fox (forkhead), T-box, Mef2, and Ets genes. Phylogenetic analysis of these genes suggests that not only the origin but the diversification of some of the major developmental metazoan transcription factor classes took place before sponges diverged from the rest of the Metazoa. Their expression during demosponge development suggests that, as in today's sophisticated metazoans, these genes may have functioned in the regulatory network of the metazoan LCA to control cell specification and regionalized gene expression during embryogenesis.

Origin of the West Nile virus responsible for an outbreak of encephalitis in the northeastern United States

In Late summer 1999, an outbreak of human encephalitis occurred in the northeastern United States that was concurrent with extensive mortality in crows (Corvus species) as well as the deaths of several exotic birds at a zoological park in the same area. Complete genome sequencing of a flavivirus isolated from the brain of a dead Chilean flamingo (Phoenicopterus chilensis), together with partial sequence analysis of envelope glycoprotein (E-glycoprotein) genes amplified from several other species including mosquitoes and two fatal human cases, revealed that West Nile (WN) virus circulated in natural transmission cycles and was responsible for the human disease. Antigenic mapping with E-glycoprotein-specific monoclonal antibodies and E-glycoprotein phylogenetic analysis confirmed these viruses as WN. This North American WN virus was most closely related to a WN virus isolated from a dead goose in Israel in 1998.

Galaxy threshing and the origin of ultra-compact dwarf galaxies in the Fornax cluster

A recent all-object spectroscopic survey centred on the Fornax cluster of galaxies has discovered a population of subluminous and extremely compact members, called 'ultra-compact dwarf' (UCD) galaxies. In order to clarify the origin of these objects, we have used self-consistent numerical simulations to study the dynamical evolution a nucleated dwarf galaxy would undergo if orbiting the centre of the Fornax cluster and suffering from its strong tidal gravitational field. We find that the outer stellar components of a nucleated dwarf are removed by the strong tidal field of the cluster, whereas the nucleus manages to survive as a result of its initially compact nature. The developed naked nucleus is found to have physical properties (e. g. size and mass) similar to those observed for UCDs. We also find that although this formation process does not have a strong dependence on the initial total luminosity of the nucleated dwarf, it does depend on the radial density profile of the dark halo in the sense that UCDs are less likely to be formed from dwarfs embedded in dark matter haloes with central 'cuspy' density profiles. Our simulations also suggest that very massive and compact stellar systems can be rapidly and efficiently formed in the central regions of dwarfs through the merging of smaller star clusters. We provide some theoretical predictions on the total number and radial number density profile of UCDs in a cluster and their dependencies on cluster masses.

Selection of species and provenances for low-rainfall areas: physiological responses of Eucalyptus cloeziana and Eucalyptus argophloia to seasonal conditions in subtropical Queensland

Responses of stomatal conductance (g(s)) and net photosynthesis (A) to changes in soil water availability, photosynthetic photon flux density (Q), air temperature (1) and leaf-to-air vapour pressure deficit (D) were investigated in 4-year-old trees of a dry inland provenance of Eucalyptus argophloia Blakely, and two dry inland provenances (Coominglah and Hungry Hills) and a humid coastal provenance (Wolvi) of Eucalyptus cloeziana F. Muell. between April 2001 and April 2002 in southeast Queensland, Australia. There were minimal differences in A, g, and water relations variables among the coastal and inland provenances of E. cloeziana but large differences between E. argophloia and E. cloeziana. E. argophloia and to a lesser extent the Hungry Hills (inland) provenance of E. cloeziana maintained relatively higher pre-dawn water potential (psi(pd)) during the dry season suggesting possible access to water at depth. Simple phenomenological models of stomatal conductance as a function of Q, T and D explained 60% of variation in gs in E. cloeziana and more than 75% in E. argophloia, when seasonal effect was incorporated in the model. A Ball-Berry model for net photosynthesis explained between 70 and 80% of observed variation in A in both species. These results have implications in matching the dry and humid provenances of E. cloeziana and E. argophloia to suitable sites in subtropical environments. (C) 2004 Elsevier B.V. All rights reserved.

Levels and probable origin of predatory scarring on humpback whales (Megaptera novaeangliae) in east Australian waters

To investigate the incidence of non-lethal predation in Southern Hemisphere whales, more than 3400 fluke-identification photographs from resight histories of 1436 east Australian humpback whales were examined for evidence of predatory markings. Photographs were obtained from 1984 to 1996 at various locations along the east coast of Australia, from northern Queensland to southern New South Wales. Photographs were classified in terms of the level and type of scarring. The possible predator and whether the markings appeared fresh were also noted. In all, 17% of identified east Australian humpbacks possessed some form of predatory scarring, 57% of which was minor and 43% major. Almost all predatory scarring was consistent with that inflicted by killer whales. Only three whales demonstrated an increase in the level of predatory scarring after their first sightings. Two incidents of fresh scarring were recorded, and one fatal killer whale attack on a humpback whale calf was directly observed. The overall level of predatory scarring found in this study is comparable to those found in studies for Northern Hemisphere humpback whales. The low incidence of adult whales showing their first sign of predatory scarring after their initial sighting, and the small number possessing recent scarring, support the idea that east Australian humpback whales experience most predatory attacks early in life.

The origin of the difference in the superconducting critical temperatures of the beta(H) and beta(L) phases of (BEDT-TTF)(2)I-3

Incommensurate lattice fluctuations are present in the beta(L) phase (T-c similar to 1.5 K) of ET2I3 (where ET is BEDT-TTF - bis(ethylenedithio)tetrathiafulvalene) but are absent in the beta(H) phase (T-c similar to 7 K). We propose that the disorder in the conformational degrees of freedom of the terminal ethylene groups of the ET molecules, which is required to stabilise the lattice fluctuations, increases the quasiparticle scattering rate and that this leads to the observed difference in the Superconducting critical temperatures, T-c, of the two phases. We calculate the dependence of T-c on the interlayer residual resistivity. Our theory has no free parameters. Our predictions are shown to be consistent with experiment. We describe experiments to conclusively test our hypothesis.

Merging of low-mass systems and the origin of the Fundamental Plane

We present a new set of dissipationless N-body simulations to examine the feasibility of creating bright ellipticals (following the Kormendy relation, hereafter KR) by hierarchically merging present-day early-type dwarf galaxies, and to study how the encounter parameters affect the location of the end product in the (mu(e))-R-e plane. We investigate the merging of one-component galaxies of both equal and different masses, the merging of two-component galaxy models to explore the effect of dark haloes on the final galaxy characteristics, and the merging of ultracompact dwarf galaxies. We find that the increase of (mu(e)) with R-e is attributable to an increase in the initial orbital energy. The merger remnants shift down in the (mu(e))-R-e plane and fail to reach the KR. Thus, the KR is not reproducible by mergers of dwarf early-type systems, rendering untenable the theory that present-day dwarfs are responsible for even a small fraction of the present-day ellipticals, unless a considerable amount of dissipation is invoked. However, we do find that present-day dwarfs can be formed by the merger of ultracompact dwarfs.

Origin of the Archean Sask craton and its extent within the Trans-Hudson orogen: evidence from Pb and Nd isotopic compositions of basement rocks and post-orogenic intrusions

U-Pb zircon ages from the exposed Sask craton are 2450-3100 Ma, from the Peter Lake Domain 2575-2640 Ma, and from rocks of the Trans-Hudson orogen 1840-1880 Ma. U-Pb monazite and zircon ages of post-orogenic pegmatites and aplites are 1770-1800 Ma. Common Pb and Sm-Nd isotopic compositions of post-orogenic intrusions, as probes of crust beneath the orogen, were compared to Sask craton rocks and ca. 1850 Ma orogenic rocks to infer the origin and subsurface distribution of the Sask craton within the internides of the Trans-Hudson orogen. Results show that post-orogenic intrusions within most of the Glennie Domain and Hanson Lake block were derived, at least in part, from Archean source materials, demonstrating that the Sask craton lies beneath Paleoproterozoic orogenic rocks present at the surface. In contrast, common Pb and Sm-Nd isotopic compositions from pegmatites and aplites of the La Ronge Domain are essentially identical with those of the Paleoproterozoic orogenic rocks into which they are intruded, indicating derivation by partial melting of similar rocks. Thus, if the Sask craton extended to the west beneath the La Ronge Domain, it was beneath the zone of melting that produced the post-orogenic intrusions, making it unlikely that the Sask craton is a detached part of the Hearne craton. Many samples from the Sask craton have elevated Pb-208/Pb-204 ratios, unlike Superior craton or Hearne craton rocks, suggesting that the Sask craton was derived from an exotic source, such as the Wyoming craton, which shares similar elevated Pb-208/Pb-204 ratios.

Evolutionary origin of Venturia canescens virus-like particles

Insect host-parasitoid interactions provide fascinating examples of evolutionary adaptations in which the parasitoid employs a variety of measures and countermeasures to overcome the immune responses of its host. Maternal factors introduced by the female wasps during egg deposition play an important role in interfering with cellular and humoral components of the host's immune defence. Some of these components actively suppress host immune components and some are believed to confer protection for the developing endoparasitoid by rather passive means. The Venturio conescens/Ephestia kuehniella parrositoid-host system is unique among other systems in that the cellular defence capacity of the host remains virtually intact after parasitization. This system raises some important questions that are discussed in this mini-review: If immune protection of the egg and the emerging larva is achieved by surface properties comprising glycoproteins and virus-like particles (VLPs) produced by the female wasp, why is the prophenoloxidose activating cascade blocked in parasitized caterpillars? Another question is the evolutionary origin of these particles, given that the functional role and structural features of V. canescens VLP proteins are more related to cellular proteins than to viruses.

On the origin of a trace inequality

Numerous authors are apparently unaware that bounds on the trace of a matrix product presented in 1995 were originally published in 1990.

The origin of modern crocodyliforms: new evidence from the Cretaceous of Australia

While the crocodyliform. lineage extends back over 200 million years (Myr) to the Late Triassic, modern forms - members of Eusuchia - do not appear until the Cretaceous. Eusuchia includes the crown group Crocodylia, which comprises Crocodyloidea, Alligatoroidea and Gavialoidea. Fossils of non-crocodylian eusuchians are currently rare and, in most instances, fragmentary. Consequently, the transition from Neosuchia to Crocodylia has been one of the most poorly understood areas of crocodyliform evolution. Here we describe a new crocodyliform from the mid-Cretaceous (98-95 Myr ago; Albian-Cenomanian) Winton Formation of Queensland, Australia, as the most primitive member of Eusuchia. The anatomical changes associated with the emergence of this taxon indicate a pivotal shift in the feeding and locomotor behaviour of crocodyliforms - a shift that may be linked to the subsequent rapid diversification of Eusuchia 20 Myr later during the Late Cretaceous and Early Tertiary. While Laurasia (in particular North America) is the most likely ancestral area for Crocodylia, the biogeographic events associated with the origin of Eusuchia are more complex. Although the fossil evidence is limited, it now seems likely that at least part of the early history of Eusuchia transpired in Gondwana.

Tradeoffs of different types of species occurrence data for use in systematic conservation planning

Data on the occurrence of species are widely used to inform the design of reserve networks. These data contain commission errors (when a species is mistakenly thought to be present) and omission errors (when a species is mistakenly thought to be absent), and the rates of the two types of error are inversely related. Point locality data can minimize commission errors, but those obtained from museum collections are generally sparse, suffer from substantial spatial bias and contain large omission errors. Geographic ranges generate large commission errors because they assume homogenous species distributions. Predicted distribution data make explicit inferences on species occurrence and their commission and omission errors depend on model structure, on the omission of variables that determine species distribution and on data resolution. Omission errors lead to identifying networks of areas for conservation action that are smaller than required and centred on known species occurrences, thus affecting the comprehensiveness, representativeness and efficiency of selected areas. Commission errors lead to selecting areas not relevant to conservation, thus affecting the representativeness and adequacy of reserve networks. Conservation plans should include an estimation of commission and omission errors in underlying species data and explicitly use this information to influence conservation planning outcomes.

Variation in hydraulic conductivity of mangroves: influence of species, salinity, and nitrogen and phosphorus availability

We investigated how species identity and variation in salinity and nutrient availability influence the hydraulic conductivity of mangroves. Using a fertilization study of two species in Florida, we found that stem hydraulic conductivity expressed on a leaf area basis (K-leaf) was significantly different among species of differing salinity tolerance, but was not significantly altered by enrichment with limiting nutrients. Reviewing data from two additional sites (Panama and Belize), we found an overall pattern of declining leaf-specific hydraulic conductivity (K-leaf) with increasing salinity. Over three sites, a general pattern emerges, indicating that native stem hydraulic conductivity (K-h) and K-leaf are less sensitive to nitrogen (N) fertilization when N limits growth, but more sensitive to phosphorus (P) fertilization when P limits growth. Processes leading to growth enhancement with N fertilization are probably associated with changes in allocation to leaf area and photosynthetic processes, whereas water uptake and transport processes could be more limiting when P limits growth. These findings suggest that whereas salinity and species identity place broad bounds on hydraulic conductivity, the effects of nutrient availability modulate hydraulic conductivity and growth in complex ways.