Geodin A magnesium salt: A novel nematocide from a southern Australian marine sponge, Geodia

A Geodia species collected from southern Australian waters of the Great Australian Eight has yielded a potent new in vitro nematocidal agent identified as geodin A Mg salt (1), a new macrocyclic polyketide lactam tetramic acid magnesium salt. The structure for 1 was assigned on the basis of detailed spectroscopic analysis.

Effects of habitat modification in mangroves on the structure of mollusc and crab assemblages

The abundance and species richness of mollusc and crab assemblages were examined in a subtropical mangrove forest in Moreton Bay, Queensland, Australia, which has been disturbed and damaged by the construction of a wooden boardwalk and a path. Sections of the forest immediately adjacent to the boardwalk and path were compared with reference areas to determine whether changes to the small-scale structural complexity within the forest affected the benthic fauna. The disturbed area was characterised by having 65-80% fewer pneumatophores, significantly fewer species and individuals of molluscs, but significantly more species and individuals of crabs than the reference areas. The abundance of mangrove pneumatophores and the attached epiphytic algae were manipulated at two sites to determine whether observed differences in these features could account for the differences in the assemblage of molluscs in the disturbed area of the forest compared with reference areas. Five experimental treatments were used: undisturbed controls, pneumatophore removals (abundance reduced by ca. 65%), epiphytic algal removals (algae removed from ca. 65% of pneumatophores), pneumatophore disturbance controls and algal disturbance controls. The experimental reduction of the abundance of mangrove pneumatophores and the associated epiphytic algae led to significant declines (by as much as 83%) in the number of molluscs utilising the substratum in the modified plots. There was no significant difference in the abundance of molluscs in the pneumatophore and algal removal plots suggesting any effect was primarily related to removal of the epiphytic algae from the surface of the pneumatophores. The responses by the biota to the changes in the physical environment demonstrate that even relatively small-scale modifications to the physical structure of subtropical mangrove forests can lead to significant effects on the diversity and abundance of macrobenthic organisms in these habitats. Such modifications have the potential to cause cascading effects at higher trophic levels with a deterioration in the value of these habitats as nursery and feeding grounds. Future efforts at conservation of these estuarine environments must focus on the prevention or reduction of modifications to the physical structure and integrity of the system, rather than just on the prevention of loss of entire patches of habitat. (C) 2000 Elsevier Science B.V. All rights reserved.

The last glacial cycle from the humid tropics of northeastern Australia: comparison of a terrestrial and a marine record

A detailed pollen record from the Ocean Drilling Program Site 820 core, located on the upper part of the continental slope off the coast of northeast Queensland, was constructed to compare with the existing pollen record from Lynch's Crater on the adjacent Atherton Tableland and allow the production of a regional picture of vegetation and environmental change through the last glacial cycle. Some broad similarities in patterns of vegetation change are revealed, despite the differences between sites and their pollen catchments, which can be related largely to global climate and sea-level changes. The original estimated time scale of the Lynch's Crater record is largely confirmed from comparison with the more thoroughly dated ODP record. Conversely, the Lynch's Crater pollen record has assisted in dating problematic parts of the ODP record. In contrast to Lynch's Crater, which reveals a sharp and sustained reduction in drier araucarian forest around 38,000 yrs BP, considered to have been the result of burning by Aboriginal people, the ODP record indicates, most likely, a stepwise reduction, dating from 140,000 yrs BP or beyond. The earliest reduction shows lack of a clear connection between Araucaria decline and increased burning and suggests that people may not have been involved at this stage. However, a further decline in araucarian forest, possibly around 45,000 yrs BP, which has a more substantial environmental impact and is not related to a time of major climate change, is likely, at least partially, the result of human burning. The suggestion, from the ODP core oxygen isotope record, of a regional sea-surface temperature increase of around 4 degrees C between about 400,000 and 250,000 yrs BP, may have had some influence on the overall decline in Araucaria and its replacement by sclerophyll vegetation. (C) 2000 Elsevier Science B.V. All rights reserved.

1,9-dimethylhypoxanthine from a southern Australian marine sponge Spongosorites species

A Spongosorites sp. collected off southern Australia has yielded 1,9-dimethylhypoxanthine (4). The structure for 4 was solved by spectroscopic analysis.

Intraspecific co-variation between egg and body size affects fertilisation kinetics of free-spawning marine invertebrates

Fertilisation of eggs of free-spawning marine invertebrates depends on factors affecting sperm concentration in the field and also on gamete characteristics such as egg size. In the free-spawning intertidal ascidian Pyura stolonifera mean egg size increased with maternal size in 2 separate populations. The largest ascidian produced eggs that were, on average, 50% greater in volume than the eggs produced by the smallest individual studied. There was no evidence to suggest that egg density varied with adult size and egg dry organic weight increased with maternal size. The fertilisation kinetics of this species were strongly affected by the variation in egg size, with the eggs of large individuals requiring much less concentrated sperm to achieve maximal levels of fertilisation success than the eggs of small individuals. We suggest that variation in egg size between individuals of different sizes and ages may be an important factor in determining fertilisation success for ascidians of this species.

Clathrins A-C: Metabolites from a southern Australian marine sponge, Clathria species

A Clathria sp. collected in the Great Australian Bight has yielded the novel metabolites clathrins A (6), B (7), and C (8). Structures were assigned to clathrins A-C on the basis of spectroscopic analysis. Clathrin A (6) represents a plausible biosynthetic intermediate that provides an inferred link between marine sesquiterpene/benzenoids and mixed terpene/shikimate biosynthesis.

Male Teachers in Feminised Teaching Areas: marching to the beat of the men's movement drums?

Calls for more male teachers are prevalent in current gender debates in education. A dominant argument in this debate is that boys are often alienated from school because of a lack of male role models in feminised areas of the school curriculum and in primary schools. Little research has investigated male teachers' accounts of their work within feminised environments. Drawing on data collected in two research studies in music education, this paper focuses on accounts given by male teachers about (a) practices adopted specifically to work with boys and (b) the role of the male music teacher. Analysis of these data suggests that some male teachers working in feminised areas of the school curriculum adopt practices which, rather than challenging dominant constructions of masculinity, sometimes reinforce gender stereotypical behaviours in boys. We argue that calls for increasing the number of male teachers in feminised areas of schooling need also to be informed by open discussion of the underlying assumptions about masculinity which teachers themselves bring to their work.

Monitoring growth in rapidly urbanizing areas using remotely sensed data

Urbanization and the ability to manage for a sustainable future present numerous challenges for geographers and planners in metropolitan regions. Remotely sensed data are inherently suited to provide information on urban land cover characteristics, and their change over time, at various spatial and temporal scales. Data models for establishing the range of urban land cover types and their biophysical composition (vegetation, soil, and impervious surfaces) are integrated to provide a hierarchical approach to classifying land cover within urban environments. These data also provide an essential component for current simulation models of urban growth patterns, as both calibration and validation data. The first stages of the approach have been applied to examine urban growth between 1988 and 1995 for a rapidly developing area in southeast Queensland, Australia. Landsat Thematic Mapper image data provided accurate (83% adjusted overall accuracy) classification of broad land cover types and their change over time. The combination of commonly available remotely sensed data, image processing methods, and emerging urban growth models highlights an important application for current and next generation moderate spatial resolution image data in studies of urban environments.

Water wave-driven seepage in marine sediments

The action of water waves moving over a porous seabed drives a seepage flux into and out of the marine sediments. The volume of fluid exchange per wave cycle may affect the rate of contaminant transport in the sediments. In this paper, the dynamic response of the seabed to ocean waves is treated analytically on the basis of pore-elastic theory applied to a porous seabed. The seabed is modelled as a semi-infinite, isotropic, homogeneous material. Most previous investigations on the wave-seabed interaction problem have assumed quasi-static conditions within the seabed, although dynamic behaviour often occurs in natural environments. Furthermore, wave pressures used in the previous approaches were obtained from conventional ocean wave theories: which are based on the assumption of an impermeable rigid seabed. By introducing a complex wave number, we derive a new wave dispersion equation, which includes the seabed characteristics (such as soil permeability, shear modulus, etc.). Based on the new closed-form analytical solution, the relative differences of the wave-induced seabed response under dynamic and quasi-static conditions are examined. The effects of wave and soil parameters on the seepage flux per wave cycle are also discussed in detail. (C) 2000 Elsevier Science Ltd. All rights reserved.

Youth suicide trends in Australian metropolitan and non-metropolitan areas, 1988-1997

Objective: The objective of this study was to examine trends in suicide among 15-34-year-olds living in Australian metropolitan and non-metropolitan areas between 1988 and 1997. Method: Suicide and population data were obtained from the Australian Bureau of Statistics. We calculated overall and method-specific suicide rates for 15-24 and 25-34-year-old males and females separately, according to area of residence defined as non-metropolitan (less than or equal to 20 000 people) or metropolitan. Results: Between 1988 and 1997 suicide rates in 15-24-year-old non-metropolitan males were consistently 50% higher than metropolitan 15-24-year-olds. In 1995-1997, for example, the rates were: 38.2 versus 25.1 per 100 000 respectively (p < 0.0001). The reverse pattern was seen in 25-34-year-old females with higher rates in metropolitan areas (7.5 per 100 000) compared with non-metropolitan areas (6.1 per 100 000, p = 0.21) in 1995-1997. There were no significant differences according to area of residence in 25-34-year-old males or 15-24-year-old females. Over the years studied we found no clear evidence that suicide rates increased to a greater extent in rural than urban areas. Rates of hanging suicide have approximately doubled in both sexes and age groups in both settings over this time. Despite an approximate halving in firearm suicide, rates remain 3-fold higher among non-metropolitan residents. Conclusion: Non-metropolitan males aged 15-24 years have disproportionately higher rates of suicide than their metropolitan counterparts. Reasons for this require further investigation. Hanging is now the most favoured method of non-metropolitan suicide replacing firearms from 10 years ago. Although legislation may reduce method-specific suicide the potential for method-substitution means that overall rates may not fall. More comprehensive interventions are therefore required.

Discorhabdin R: A new antibacterial Pyrroloiminoquinone from two latrunculiid marine sponges, Latrunculia sp and Negombata sp.

Two sponge's belonging to the family Latrunculiidae (Negombata and Latrunculia sp.) collected during scientific trawling operations in Prydz Bay, Antarctica, and by scuba off Port Campbell, Victoria, have yielded a new antibacterial pyrroloiminoquinone, discorhabdin R (2). The structure was assigned as 2 on the basis of detailed, spectroscopic analysis and comparison with the known co-metabolite discorhabdin B (3).

Lorneamides A and B: Two new aromatic amides from a southern Australian marine actinomycete

A marine actinomycete (MST-MA190) isolated from a sample of beach sand collected near Lorne on the southwest coast of Victoria, Australia, has yielded two new aromatic amides, lorneamide A (1) and lorneamide B (2). The lorneamides belong to a novel class of tri-alkyl-substituted benzenes, and their structures were determined by spectroscopic methods.

Phorbasin A: A novel diterpene from a southern Australian marine sponge, phorbas species

A southern Australian Phorbas species has yielded a novel diterpene, phorbasin A (1), possessing an unprecedented carbon skeleton. The structure for phorbasin A was determined by detailed spectroscopic analysis.

Marine bioprospecting - Trawling for treasure and pleasure

This Microreview seeks to highlight the molecular diversity present in marine organisms, and illustrate by example some of the challenges encountered in exploring this resource. Marine natural products exhibit an impressive array of structural motifs, many of which are derived from biosynthetic pathways that are uniquely marine, Most importantly some marine metabolites possess noteworthy biological activities, activities that have potential application outside marine ecosystems, such as antibiotics, antiparasitics, anticancer agents etc... The isolation, spectroscopic characterisation and assignment of stereostructures to these unusual metabolites is both challenging and rewarding. Examples featured in this Microreview follow a common theme in that they are all recent accounts of the isolation of natural products from Australian marine sponges, carried out in the laboratories of the author. In addition to presenting brief comments on specific structure elucidation strategies, an effort is made to emphasize techniques for solving stereochemical issues, as well as to speculate on the biosynthetic origins of some of these exotic marine natural products.