Effects of settler size and density on early post-settlement survival of Ciona intestinalis in the field

Effects of variation in larval quality on post-metamorphic performance in marine invertebrates are increasingly apparent. Recently, it has been shown that variation in offspring size can also strongly affect post-settlement survival, but variation in environmental conditions can mediate this effect. The quality of habitat into which marine invertebrate larvae settle can vary markedly, and 1 influence on quality is the number of conspecifics present. We tested the effects of settler size and settler density on early (1 wk after settlement) post-settlement survival in the field for the solitary ascidian Ciona intestinalis. Larger settlers survived better than smaller settlers, within and among groups of siblings. Increases in the density of settlers decreased survival, but the density-dependent effects were much stronger for smaller settlers. We suggest that larger settlers are better able to cope with intra-specific competition because they have greater energetic reserves or a greater capacity to feed than smaller settlers.

Field assessment of thermal after-ripening time for dormancy release prediction in Lolium rigidum seeds

Dormancy release was studied in four populations of annual ryegrass (Lolium rigidum) seeds to determine whether loss of dormancy in the field can be predicted from temperature alone or whether seed water content (WC) must also be considered. Freshly matured seeds were after-ripened at the northern and southern extremes of the Western Australian cereal cropping region and at constant 37degreesC. Seed WC was allowed to fluctuate with prevailing humidity, but full hydration was avoided by excluding rainfall. Dormancy was measured regularly during after-ripening by germinating seeds with 12-hourly light or in darkness. Germination was lower in darkness than in light/dark and dormancy release was slower when germination was tested in darkness. Seeds were consistently drier, and dormancy release was slower, during after-ripening at 37degreesC than under field conditions. However, within each population, the rate of dormancy release in the field (north and south) in terms of thermal time was unaffected by after-ripening site. While low seed WC slowed dormancy release in seeds held at 37degreesC, dormancy release in seeds after-ripened under Western Australian field conditions was adequately described by thermal after-ripening time, without the need to account for changes in WC elicited by fluctuating environmental humidity.

Potential triggers for akinete differentiation in an Australian strain of the cyanobacterium Cylindrospermopsis raciborskii (AWT 205/1)

Understanding the triggers for some cyanobacteria of the Nostocales and Stigonematales orders to produce specialised reproductive cells termed akinetes, is very important to gain further insights into their ecology. By improving our understanding of their life cycle, appropriate management options may be devised to control the formation of these cells, and therefore the potential bloom inoculum which they are thought to provide, may be reduced. This study investigated the effect of chemical (phosphorus limitation), and environmental variables (temperature shock) on akinete differentiation in the freshwater cyanobacterium Cylindrospermopsis raciborskii (AWT 205/1). From the preliminary results, it is suggested that the availability of phosphorus and changes in temperature were a necessary requirement for the formation of akinetes in this particular strain of C. raciborskii. In the four phosphorus treatments investigated (0, 3, 38 and 75 mug l(-1) P), only the two higher treatments produced akinetes (approximately 220 ml(-1)). When the first akinetes were observed in the 38 and 75 mug l(-1) P treatments, filterable reactive phosphorus (FRP) concentrations in the medium were approximately 22 and 52 mug l(-1) P, respectively, indicating that there was no phosphorus limitation. In the temperature shock experiment, akinetes were observed in the 15 and 20degreesC treatments. However, akinetes were degraded (pale yellow colour, limited swelling and shrivelled edges) and in much lower concentrations, which was thought to be a result of the daily temperature shock. We suggest that the formation of akinetes in C. raciborskii (AWT 205/1) can be triggered by an initial temperature shock and that phosphorus is a necessary requirement to allow further growth and full development of akinetes.

Neogene and Quaternary rollback evolution of the Tyrrhenian Sea, the Apennines, and the Sicilian Maghrebides

Reconstruction of the evolution of the Tyrrhenian Sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 Ma. It involved two episodes of back arc extension, which were induced by the rollback of a west dipping subducting slab. The first period of extension (10-6 Ma) was prominent in the northern Tyrrhenian Sea and in the western part of the southern Tyrrhenian Sea. The second period of extension, mainly affected the southern Tyrrhenian Sea, began in the latest Messinian (6-5 Ma) and has been accompanied by subduction rollback at rates of 60-100 km Myr(-1). Slab reconstruction, combined with paleomagnetic and paleogeographic constraints, indicates that in the central Apennines, the latest Messinian (6-5 Ma) arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike-slip faults. These processes resulted in the formation of a narrow subducting slab beneath the Ionian Sea that has undergone faster subduction rollback and induced extreme rates of back arc extension.

Mediatizing educational policy: The journalistic field, science policy, and cross-field effects

This paper is concerned to demonstrate the usefulness of the theory of Bourdieu, including the concepts of field, logics of practice and habitus, to understanding relationships between media and policy, what Fairclough has called the 'mediatization' of policy. Specifically, the paper draws upon Bourdieu's accessible account of the journalistic field as outlined in On television and journalism. The usefulness of this work is illustrated through a case study of a recent Australian science policy, The chance to change. As this policy went through various iterations and media representations, its naming and structure became more aphoristic. This is the mediatization of contemporary policy, which often results in policy as sound bite. The case study also shows the cross-field effects of this policy in education, illustrating how today educational policy can be spawned from developments in other public policy fields.

The Development of Science Education Research in Brazil and Contributions from the History and Philosophy of Science

Over the last 50 years a new research area, science education research, has arisen and undergone singular development worldwide. In the specific case of Brazil, research in science education first appeared systematically 40 years ago, as a consequence of an overall renovation in the field of science education. This evolution was also related to the political events taking place in the country. We will use the theoretical work of Rene Kaes on the development of groups and institutions as a basis for our discussion of the most important aspects that have helped the area of science education research develop into an institution and kept it operating as such. The growth of this area of research can be divided into three phases: The first was related to its beginning and early configurations; the second consisted of a process of consolidation of this institution; and the third consists of more recent developments, characterised by a multiplicity of research lines and corresponding challenges to be faced. In particular, we will analyse the special contributions to this study gleaned from the field known as the history and philosophy of science.

Galaxy threshing and the origin of intracluster stellar objects

We numerically investigate the dynamical evolution of non-nucleated dwarf elliptical/spiral galaxies (dE) and nucleated ones (dE,Ns) in clusters of galaxies in order to understand the origin of intracluster stellar objects, such as intracluster stars (ICSs), GCs (ICGCs), and ultracompact dwarfs (UCDs) recently discovered by all-object spectroscopic survey centred on the Fornax cluster of galaxies. 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 the UCD formation process, 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 halos 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 GCs. GCs initially in the outer part of dE and dE,Ns are found to be stripped to form ICGCs.

The sound field generated by tethered stingless bees (Melipona scutellaris): inferences on its potential as a recruitment mechanism inside the hive

In stingless bees, recruitment of hive bees to food sources involves thoracic vibrations by foragers during trophallaxis. The temporal pattern of these vibrations correlates with the sugar concentration of the collected food. One possible pathway for transfering such information to nestmates is through airborne sound. In the present study, we investigated the transformation of thoracic vibrations into air particle velocity, sound pressure, and jet airflows in the stingless bee Melipona scutellaris. Whereas particle velocity and sound pressure were found all around and above vibrating individuals, there was no evidence for a jet airflow as with honey bees. The largest particle velocities were measured 5 mm above the wings (16.0 +/- 4.8 mm s(-1)). Around a vibrating individual, we found maximum particle velocities of 8.6 +/- 3.0 mm s(-1) (horizontal particle velocity) in front of the bee`s head and of 6.0 +/- 2.1 mm s(-1) (vertical particle velocity) behind its wings. Wing oscillations, which are mainly responsible for air particle movements in honey bees, significantly contributed to vertically oriented particle oscillations only close to the abdomen in M. scutellaris(distances <= 5 mm). Almost 80% of the hive bees attending trophallactic food transfers stayed within a range of 5 mm from the vibrating foragers. It remains to be shown, however, whether air particle velocity alone is strong enough to be detected by Johnston`s organ of the bee antenna. Taking the physiological properties of the honey bee`s Johnston`s organ as the reference, M. scutellaris hive bees are able to detect the forager vibrations through particle movements at distances of up to 2 cm.

Nestmate recognition in a Neotropical swarm-founding wasp: no effect of seasonality on tolerance of alien conspecifics

Previous study revealed that the swarm-founding wasp Polybia paulista is accurately able to distinguish nestmates from non-nestmates in the summer. However, the risk of accepting alien intruders is considered to be low in winter colonies, and additionally brood production is limited in 30-40% of colonies during the winter in this species. Thus, it is expected that colonies might lower their acceptance threshold and accept some conspecific wasps from alien colonies in winter. We conducted field experiments to examine tolerance of conspecific (nestmate and non-nestmate) females in winter. In contrast to our prediction, our colonies did not accept any individuals from alien colonies. We suggest that P. paulista exhibits the colony-specific acceptance threshold in winter, and colonies that produced brood in their nests may have raised the acceptance threshold even if the risk of accepting alien intruders is low in winter.

Characterization of a microcystin and detection of microcystin synthetase genes from a Brazilian isolate of Nostoc

A nostocalean nitrogen-fixing cyanobacterium isolated from an eutrophic freshwater reservoir located in Piracicaba, Sao Paulo, Brazil, was evaluated for the production of hepatotoxic cyclic heptapeptides, microcystins. Morphologically this new cyanobacterium strain appears closest to Nostoc, however, in the phylogenetic analysis of 165 rRNA gene it falls into a highly stable cluster distantly only related to the typical Nostoc cluster. Extracts of Nostoc sp. CENA88 cultured cells, investigated using ELISA assay, gave positive results and the microcystin profile revealed by ESI-Q-TOF/MS/MS analysis confirmed the production of [Dha(7)]MCYST-YR. Further, Nostoc sp. CENA88 genomic DNA was analyzed by PCR for sequences of mcyD, mcyE and mcyG genes of microcystin synthetase (mcy) cluster. The result revealed the presence of mcyD, mcyE and mcyG genes with similarities to those from mcy of Nostoc sp. strains 152 and IO-102-I and other cyanobacterial genera. The phylogenetic tree based on concatenated McyG, McyD and McyE amino acids clustered the sequences according to cyanobacterial genera, with exception of the Nostoc sp. CENA88 sequence, which was placed in a clade distantly related from other Nostoc strains, as previously observed also in the 165 rRNA phylogenetic analysis. The present study describes for the first time a Brazilian Nostoc microcystin producer and also the occurrence of demethyl MCYST-YR variant in this genus. The sequenced Nostoc genes involved in the microcystin synthesis can contribute to a better understanding of the toxigenicity and evolution of this cyanotoxin. (C) 2009 Elsevier Ltd. All rights reserved.

Organization, evolution and transcriptional profile of hexamerin genes of the parasitic wasp Nasonia vitripennis (Hymenoptera: Pteromalidae)

Hexamerins and prophenoloxidases (PPOs) proteins are members of the arthropod-haemocyanin superfamily. In contrast to haemocyanin and PPO, hexamerins do not bind oxygen, but mainly play a role as storage proteins that supply amino acids for insect metamorphosis. We identified seven genes encoding hexamerins, three encoding PPOs, and one hexamerin pseudogene in the genome of the parasitoid wasp Nasonia vitripennis. A phylogenetic analysis of hexamerins and PPOs from this wasp and related proteins from other insect orders suggests an essentially order-specific radiation of hexamerins. Temporal and spatial transcriptional profiles of N. vitripennis hexamerins suggest that they have physiological functions other than metamorphosis, which are arguably coupled with its lifestyle.

Microcystin production by a freshwater spring cyanobacterium of the genus Fischerella

We investigated the production of a hepatotoxic, cyclic heptapeptide, microcystin, by a filamentous branched cyanobacterium belonging to the order Stigonematales, genus Fischerella. The freshwater Fischerella sp. strain CENA161 was isolated from spring water in a small concrete dam in Piracicaba, Sao Paulo State, Brazil, and identified by combining a morphological description with 16S rRNA gene sequencing and phylogenetic analysis. Microcystin (MCYST) analysis performed using an ELISA assay on cultured cells gave positive results. High performance liquid chromatography-mass spectrometry (HPLC-MS) analysis detected 33.6 mu g MCYST-LR per gram dry weight of cyanobacterial cells. Microcystin profile revealed by quadrupole time-of-flight tandem mass spectrometry (Q-TOF-MS/MS) analysis confirmed the production of MCYST-LR. Furthermore, genomic DNA was analyzed by PCR for sequences similar to the ketosynthase (KS) domain of the type I polyketide synthase gene, which is involved in microcystin biosynthesis. This revealed the presence of a KS nucleotide fragment similar to the mcyD and ndaD genes of the microcystin and nodularin synthetase complexes. Phylogenetic analysis grouped the Fischerella KS sequence together with mcyD sequences of the three known microcystin synthetase operon (Microcystis, Planktothrix and Anabaena) and ndaD of the nodularin synthetase operon, with 100% bootstrap support. Our findings demonstrate that Fischerella sp. CENA161 produces MYCST-LR and for the first time identify a nucleotide sequence putatively involved in microcystin synthesis in this genus. (C) 2009 Elsevier Ltd. All rights reserved.