2011 Postgraduate Research Competition - UNSW Science - The ...

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Weak jaws linked to extinction in Tassie tiger
Marie Attard, Steve Wroe and Tracey Rogers
School of Biological, Earth & Environmental Sciences
Abstract
With rapidly increasing rates of contemporary extinctions, predicting extinction vulnerability
has become a key challenge in ecology. Understanding risk factors associated with
extinction, such as diet, may assist future conservation efforts. Australia’s iconic species, the
thylacine, or commonly known as the Tassie tiger was a large carnivore and the only
marsupial to become extinct in Tasmania following European settlement. The factors
involved in its extinction have been argued, yet the underlying cause of their decline remains
incomplete. Using advanced computer modelling techniques, we simulated various
predatory behaviours to see patterns of stress in the skull. Simulations of thylacine skull
performance were compared to living marsupial carnivores capable of catching large
animals. Our findings suggest that the thylacine’s jaws were too weak to capture and kill
large prey. Rather, their exceptionally long snout was better suited to snapping up smaller,
more agile prey. Specialising in small prey may have short-term success but is a long-term risk;
as they are among the first to become extinct when the ecosystem becomes destabilised.
With this inherent vulnerability, thylacines may have simply been unable to cope with
environmental disturbances such as intensive hunting and habitat degradation following
European arrival.
Impact of Micro-fabricated Surfaces and
Protozoan Grazing on Marine Microbial Biofilms
Abstract
Min Hui Low, Staffan Kjelleberg and Diane McDougald
School of Biotechnology & Biomolecular Sciences
The impact of protozoan grazing on microbial biofilms developed on micro-fabricated polydimethyl
siloxane (PDMS) surfaces was assessed after 20 days of exposure in the marine
environment. Four different PDMS surfaces were used; 1, 2, 4 and 10 µm parallel grooves with
equal widths and heights for the 4 and 10 µm fabrications, and equal widths but 0.5 µm in
height for the 1 and 2 µm surfaces. At a depth of 2 meters in waters off the Sydney coast,
biofilms were pre-established on the different micro-fabricated surfaces within environmental
diffusion chambers for 15 days in the absence of large protozoans, then challenged with the
surface feeding flagellate, Rhynchomonas nasuta for 5 days before sampling. 3D-images of
biofilms were scanned using confocal laser scanning microscope (CLSM) and biomass
quantified by IMARISTM software. Extracted DNA from the microbial community was
analysed by 16S- terminal-restriction length polymorphism (T-RFLP) to investigate community
composition differences on surfaces with and without of R. nasuta. Based on MDS and
biovolume difference, R. nasuta grazing played a more crucial role in changing community
compositions compared to micro-fabricated surfaces but biovolume differences on microfabricated
surfaces is little between the presence and absence of R nasuta.
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