Sink or swim- ageing in Australia

As the number of people under the age of 65 declines, the number over 65 will double in the next half century. By 2031, it is estimated those over 65 will account for more than a quarter of the Australian population. The fastest rate of growth will be in the over-85-years category, projected to double over the next 20 years and to triple over 50 years to include 2.3 million people. Health care providers cannot afford to wait for the inevitable crises this vast demographic shift will provoke. To meet these future demands, educational and health care institutes should consider establishing interdisciplinary think-tanks for multidisciplinary research, policy development and innovations in aged care and health service delivery.
Aust Health Rev 2005: 29(2): 146-150

A new method for resolving uncertainty of energy requirements in large water breathers: The 'mega-flume' seagoing swim-tunnel respirometer

Body size is a key determinant of metabolic rate, but logistical constraints have led to a paucity of energetics measurements from large water-breathing animals. As a result, estimating energy requirements of large fish generally relies on extrapolation of metabolic rate from individuals of lower body mass using allometric relationships that are notoriously variable. Swim-tunnel respirometry is the 'gold standard' for measuring active metabolic rates in water-breathing animals, yet previous data are entirely derived from body masses <10 kg - at least one order of magnitude lower than the body masses of many top-order marine predators. Here, we describe the design and testing of a new method for measuring metabolic rates of large water-breathing animals: a c. 26 000 L seagoing 'mega-flume' swim-tunnel respirometer. We measured the swimming metabolic rate of a 2·1-m, 36-kg zebra shark Stegostoma fasciatum within this new mega-flume and compared the results to data we collected from other S. fasciatum (3·8-47·7 kg body mass) swimming in static respirometers and previously published measurements of active metabolic rate measurements from other shark species. The mega-flume performed well during initial tests, with intra- and interspecific comparisons suggesting accurate metabolic rate measurements can be obtained with this new tool. Inclusion of our data showed that the scaling exponent of active metabolic rate with mass for sharks ranging from 0·13 to 47·7 kg was 0·79; a similar value to previous estimates for resting metabolic rates in smaller fishes. We describe the operation and usefulness of this new method in the context of our current uncertainties surrounding energy requirements of large water-breathing animals. We also highlight the sensitivity of mass-extrapolated energetic estimates in large aquatic animals and discuss the consequences for predicting ecosystem impacts such as trophic cascades.

The comparative energetics and growth strategies of sympatric Antarctic and subantarctic fur seal pups at Iles Crozet

The period of maternal dependence is a time during which mammalian infants must optimise both their growth and the development of behavioural skills in order to successfully meet the demands of independent living. The rate and duration of maternal provisioning, post-weaning food availability and climatic conditions are all factors likely to influence the growth strategies of infants. While numerous studies have documented differences in growth strategies at high taxonomic levels, few have investigated those of closely related species inhabiting similar environments. The present study examined the body composition, metabolism and indices of physiological development in pups of Antarctic fur seals (Arctocephalus gazella) and subantarctic fur seals (Arctocephalus tropicalis), congeneric species with different weaning ages (4 months and 10 months, respectively), during their overlap in lactation at a sympatric breeding site in the Iles Crozet. Body lipid reserves in pre-moult pups were significantly greater (t₂₈=2.73, P<0.01) in subantarctic (26%) than Antarctic fur seals (22%). Antarctic fur seal pups, however, had significantly higher (t₂₆=3.82, P<0.001) in-air resting metabolic rates (RMR; 17.1±0.6 ml O₂ kg^-1 min^-1) than subantarctic fur seal pups (14.1±0.5 ml O2 kg^-1 min^-1). While in-water standard metabolic rate (SMR; 22.9±2.5 ml O2 kg^-1 min^-1) was greater than in-air RMR for Antarctic fur seal pups (t₉=2.59, P<0.03), there were no significant differences between in-air RMR and in-water SMR for subantarctic fur seal pups (t₁₂=0.82, P>0.4), although this is unlikely to reflect a greater ability for pre-moult pups of the latter species to thermoregulate in water. Pup daily energy expenditure was also significantly greater (t₂₇=2.36, P<0.03) in Antarctic fur seals (638±33 kJ kg^-1 day^-1) than in subantarctic fur seals (533±33 kJ kg^-1 day^-1), which corroborates observations that pups of the former species spend considerably more time actively learning to swim and dive. Consistent with this observation is the finding that blood oxygen storage capacity was significantly greater (t₉=2.81, P<0.03) in Antarctic (11.5%) than subantarctic fur seal (8.9%) pups. These results suggest that, compared with subantarctic fur seals, Antarctic fur seal pups adopt a strategy of faster lean growth and physiological development, coupled with greater amounts of metabolically expensive behavioural activity, in order to acquire the necessary foraging skills in time for their younger weaning age.

Variation in plasma leptin levels in response to fasting in Antarctic fur seals (Arctocephalus gazella)

Plasma leptin levels were determined in 8 lactating female and 20 pup Antarctic fur seals (Arctocephalus gazella) during fasting periods of normal duration. Plasma leptin levels ranged from 1.35-3.19 ng·ml^-1 in lactating females and 1.79-4.80 ng·ml^-1 in pups and were not positively correlated with body mass or condition. A negative trend, however, was observed between plasma leptin levels and body condition in lactating females upon their arrival at the colony following a foraging trip (beginning of fast). In accordance with findings in other species, plasma leptin levels dropped significantly (P<0.02) in response to the 17-19% drop in body mass experienced by pups during fasting. In contrast, plasma leptin levels in lactating females increased during the first 24 h of fasting before decreasing throughout the remaining 48 h of the fast. This unexpected result could be due to the high level of energy expenditure by seals as they swim back to the colony (i.e. post-exercise response) or may be influenced by the intense suckling activity experienced by females during the onshore fasting periods. The results of this study support recent findings in other carnivore species which suggest the primary physiological role of leptin in these species may not necessarily be as a signal of the magnitude of body energy reserves.

Understanding science

"Understanding Science is about breakdown of meaning, breakdown of relationship, trying to exist in that space between meaninglessness and understanding, at its cusp, its node, its no-man’s land.. It is a melting pot of more than just fragments of images, there are clusters of things, ideas, sounds, words, that swim in and out of your attention. I wanted this film to be a dense multidimensional collage of automatic writing, sound poetry and abstracting strings of images." http://www.innersense.com.au/mif/debruyn_films.html

Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri

Hybridization between closely related species often leads to reduced viability or fertility of offspring. Complete failure of hybrid offspring (post-zygotic hybrid incompatibilities) may have an important role in maintaining the integrity of reproductive barriers between closely related species. We show elsewhere that in Peron's tree frog, Litoria peronii, males more closely related to a female sire more offspring in sperm competition with a less related rival male. Observations of rare 'phenotypic intermediate' males between L. peronii and the closely related L. tyleri made us suggest that these relatedness effects on siring success may be because of selection arising from risks of costly hybridization between the two species. Here, we test this hypothesis in an extensive sperm competition experiment, which shows that there is no effect of species identity on probability of fertilization in sperm competition trials controlling for sperm concentration and sperm viability. Instead, there was a close agreement between a male's siring success in isolation with a female and his siring success with the same female in competition with a rival male regardless of species identity. Offspring viability and survival, however, were strongly influenced by species identity. Over a 14-day period, hybrid offspring suffered increasing mortality and developed more malformations and an obvious inability to swim and right themselves, leading to compromised probability of survival. Thus, hybridization in these sympatric tree frogs does not compromise fertilization but has a strong impact on offspring viability and opportunity for reinforcement selection on mate choice for conspecific partners.

Stressor categorization : acute physical and psychological stressors elicit distinctive recruitment patterns in the amygdala and in medullary noradrenergic cell groups

It has been hypothesized that the brain categorizes stressors and utilizes neural response pathways that vary in accordance with the assigned category. If this is true, stressors should elicit patterns of neuronal activation within the brain that are category-specific. Data from previous immediate–early gene expression mapping studies have hinted that this is the case, but interstudy differences in methodology render conclusions tenuous. In the present study, immunolabelling for the expression of c-fos was used as a marker of neuronal activity elicited in the rat brain by haemorrhage, immune challenge, noise, restraint and forced swim. All stressors elicited c-fos expression in 25–30% of hypothalamic paraventricular nucleus corticotrophin-releasing-factor cells, suggesting that these stimuli were of comparable strength, at least with regard to their ability to activate the hypothalamic–pituitary–adrenal axis. In the amygdala, haemorrhage and immune challenge both elicited c-fos expression in a large number of neurons in the central nucleus of the amygdala, whereas noise, restraint and forced swim primarily elicited recruitment of cells within the medial nucleus of the amygdala. In the medulla, all stressors recruited similar numbers of noradrenergic (A1 and A2) and adrenergic (C1 and C2) cells. However, haemorrhage and immune challenge elicited c-fos expression in subpopulations of A1 and A2 noradrenergic cells that were significantly more rostral than those recruited by noise, restraint or forced swim. The present data support the suggestion that the brain recognizes at least two major categories of stressor, which we have referred to as ‘physical’ and ‘psychological’. Moreover, the present data suggest that the neural activation footprint that is left in the brain by stressors can be used to determine the category to which they have been assigned by the brain.

Fiber-specific responses of muscle glycogen repletion in fasted rats physically active during recovery from high-intensity physical exertion

Mild physical activity performed immediately after a bout of intense exercise in fasting humans results in net glycogen breakdown in their slow oxidative (SO) muscle fibers and glycogen repletion in their fast twitch (FT) fibers. Because several animal species carry a low proportion of SO fibers, it is unclear whether they can also replenish glycogen in their FT fibers under these conditions. Given that most skeletal muscles in rats are poor in SO fibers (<5%), this issue was examined using groups of 24-h fasted Wistar rats (n = 10) that swam for 3 min at high intensity with a 10% weight followed by either a 60-min rest (passive recovery, PR) or a 30-min swim with a 0.5% weight (active recovery, AR) preceding a 30-min rest. The 3-min sprint caused 61–79% glycogen fall across the muscles examined, but not in the soleus (SOL). Glycogen repletion during AR without food was similar to PR in the white gastrocnemius (WG), where glycogen increased by 71%, and less than PR in both the red and mixed gastrocnemius (RG, MG). Glycogen fell by 26% during AR in the SOL. Following AR, glycogen increased by 36%, 87%, and 37% in the SOL, RG, and MG, respectively, and this was accompanied by the sustained activation of glycogen synthase and inhibition of glycogen phosphorylase in the RG and MG. These results suggest that mammals with a low proportion of SO fibers can also replenish the glycogen stores of their FT fibers under extreme conditions combining physical activity and fasting.

Understanding science

Understanding Science is about breakdown of meaning, breakdown of relationship, trying to exist in that space between meaninglessness and understanding, at its cusp, its node, its no-man's land.. It is a melting pot of more than just fragments of images, there are clusters of things, ideas, sounds, words, that swim in and out of your attention. I wanted this film to be a dense multidimensional collage of automatic writing, sound poetry and abstracting strings of images.

Program notes: Scratch Film Festival. UWA. Perth 1997

Firsts: performing ways first year teachers experience identity transformation

This thesis reports on research showing the survival discourse of beginning teaching has shifted from sink or swim metaphors to describe surviving transition shock and classroom management concerns to surviving contract employment. Beginning teachers are neither sinking nor swimming in this liminal state. Rather, it is as though they are on a lifeboat where they cannot feel like a ‘real’ teacher until they can operate with certainty.

Interrogating the experiences of beginning teachers, and the transformation of their identity in their first year (1yr) of teaching, the thesis explores research participants’ firsts as epiphanic or revelatory moments of identity transformation. Participants were followed for three years from upon completion of their teacher education, through their first year of teaching, up to the beginning of their third year in the profession. The major finding was that while contemporary understandings of professional identity highlight the transformative nature of the phenomenon,  contract employment had the most impact on these teachers’ identity transformation.

Teachers’ perceptions of their own professional identity affect their efficacy and professional development as well as their ability and willingness to cope with educational change (Beijaard, Verloop & Vermunt 2000). It has been reported by the Australian Education Union (AEU) and in the Victorian media in recent years that up to 50% of beginning teachers are leaving the profession within their first five years. The reasons given for this level of
attrition include workload, pay, and behaviour management, among the top concerns of beginning teachers. These categories have positioned beginning teachers in a survival discourse for many years, yet there is more to beginning teachers’ intentions to leave than their struggles to survive in the classroom. More recently in Victoria what it means to ‘survive’ has shifted to surviving the pervasive contractual nature of beginning teachers’
employment conditions.

This qualitative study seeks to question what remains concealed with regard to beginning teachers’ experiences through an investigation of the differences between and within individuals, allowing categories of description to emerge from the data rather than pre-determining categories of investigation. Data was collected from twelve participants through individual semi-structured interviews and written communication. A theatre-based research approach to representing the participants’ experiences was employed, culminating in a performance titled ‘The First Time’. The processes of scripting, rehearsing, and performing, were utilised to analyse and represent the data to expert audiences. In an aim to uncover questions that have been buried by answers, the research is oriented as a
phenomenographic inquiry. This mode of inquiry seeks to describe, analyse, and understand (Marton 1981) the qualitatively different experiences 1yr teachers undergo in their identity formation and transformation.

The results of this research reveal the destabilising effect of short-term contracts so prevalent in the current context; that status and belonging are central to 1yr teachers’ identity work. Status and belonging are positioned within survival, liminal, and hegemonic discourses; and expressed through artefacts as symbols of belonging. The low status ascribed to contractual work has a clear impact on beginning teachers’ commitment to the profession.

A review of long-distance movements by marine turtles, and the possible role of ocean currents

Sea turtle movements often occur in open-sea unsheltered areas, and are therefore likely to be influenced by major oceanographic processes. Only recently has work started to examine the possible relationships of these movements with dynamic oceanic features, and consequently a clear picture of such interaction is only available in a few cases. Newborn sea turtles are thought to rely on oceanic currents to reach their pelagic nursery habitats. The actual extent and timing of these developmental migrations are known for only a few populations, but these movements probably last several years and range over thousands of km. Large juveniles that have been tracked during their pelagic stage were found to make long-distance movements, sometimes swimming against the prevailing currents. Older juveniles of most species leave the pelagic habitat to recruit to neritic developmental habitats. This is a very poorly documented phase of the sea turtle life-cycle, and the few available indications show that turtles may have to swim actively for enormous distances to counterbalance their previous drift with the current. The course and extent of adult postnesting migrations vary greatly among different turtle species, but two main patterns are evident. Some species, like green, hawksbill and loggerhead turtles, shuttle between the nesting beach and a specific feeding area used for the entire inter-reproductive period. In these cases, individuals swim, rather than drift, to complete their journeys, with possible advection due to currents sometimes helping them to quickly reach their target, but sometimes providing navigational challenges. Other species such as the olive ridley and the leatherback turtle, leave the coastal nesting areas to reach the pelagic environment where they forage, and perform wandering movements. Major oceanographic processes (such as main currents and eddies) have been recently shown to have a remarkable influence on leatherback movements, making it questionable whether these journeys are to be considered migrations or, rather, prolonged stays in vast feeding areas.

Island-finding ability of marine turtles

Green turtles (Chelonia mydas) swim from foraging grounds along the Brazilian coast to Ascension Island to nest, over 2200 km distant in the middle of the equatorial Atlantic. To test the hypothesis that turtles use wind-borne cues to locate Ascension Island we found turtles that had just completed nesting and then moved three individuals 50 km northwest (downwind) of the island and three individuals 50 km southeast (upwind). Their subsequent movements were tracked by satellite. Turtles released downwind returned to Ascension Island within 1, 2 and 4 days, respectively. By contrast, those released upwind had far more difficulty in relocating Ascension Island, two eventually returning after 10 and 27 days and the third heading back to Brazil after failing to find its way back to the island. These findings strongly support the hypothesis that wind-borne cues are used by turtles to locate Ascension Island.

Dive angles for a green turtle (Chelonia mydas)

The depth and swim speed of a green turtle (Chelonia mydas) were measured during the internesting period in Cyprus. For dives to the seabed (U-dives) we used these data to determine dive angles. Typically the turtle initially descended at a steep angle ([similar]60°) but as the dive continued this angle lessened until the turtle approached the seabed at an average angle of [similar]15°. This systematic change in descent angle is consistent with the prediction that the energetic implications of dive angle are most important at the start of the dive when the turtle is fighting to overcome its positive buoyancy. On leaving the seabed, the turtle often seemed to rise passively.

The ocean sunfish Mola mola : insights into distribution, abundance and behaviour in the Irish and Celtic Seas

Here we provide baseline data on the distribution and abundance of Mola mola within the Irish and Celtic Seas, made during aerial surveys from June to October during 2003–2005. These data were considered in conjunction with concurrent observations of three potential jellyfish prey species found throughout the region: Rhizostoma octopus, Chrysaora hysoscella and Cyanea capillata. A total area of 7850 km2 was surveyed over the three years with an observed abundance of 68 sunfish giving a density of 0.98 ind/100 km2. Although modest, these findings highlight that the species is more common than once thought around Britain and Ireland and an order of magnitude greater than the other apex jellyfish predator found in the region, the leatherback turtle (Dermochelys coriacea). Furthermore, the distribution of sunfish sightings was inconsistent with the extensive aggregations of Rhizostoma octopus found throughout the study area. The modelled distributions of predator–prey co-occurrence (using data for all three jellyfish species) was less than the observed co-occurrence with the implication that neither jellyfish nor sunfish were randomly distributed but co-occurred more in the same areas than expected by chance. Finally, observed sunfish were typically small ([similar]1 m or less) and seen to either bask or actively swim at the surface.

Exploring first year teachers’ identity transformation through theatre-based research

Why are beginning teachers leaving the profession in large numbers? Are they leaving because of their dissatisfaction with teaching? Are they leaving because of the conditions of their work that shape their identity? Teacher identity work emphasises it is important beginning teachers understand their professional identity as something shifting, fluid and emerging – not fixed. These and other water metaphors – such as ‘washout’, ‘sink or swim’, and ‘thrown in the deep end’ – are often used to describe beginning teachers’ experiences. Such words and metaphors assist to portray the fluid and unpredictable nature of identity transformation. However, these survival terms also influence beginning teachers to believe that their transition to teaching will be difficult. Recently there has been an increased concern over beginning teacher attrition linked to the difficulties they encounter in their early years of teaching. Yet the conditions of beginning teachers’ work in Victorian schools in Australia – including the contractual nature of employment of first year (1yr) teachers – encourage these 1yr practitioners to view their work as semi-permanent. As a result these 1yr teachers do not see themselves as teaching for extended periods of time, as was once the case. Throughout 2011 twelve 1yr teachers shared their experiences of identity transformation in semi-structured interviews with the researcher. Their interview data was analysed through a theatre-based research method, examining how first experiences shape teachers’ future practice and identity. This presentation includes excerpts from the theatre-based research performance ‘The First Time’, and expands on the methodological approaches taken to analyse the data in a way that reflects the fluid and unpredictable nature of teachers’ identity formation and transformation. This qualitative study allows categories of description to emerge from the data rather than pre-determining categories of investigation. As such the processes of scripting, rehearsing, and performing, were utilised to analyse and re-present the data. In an aim to uncover questions that have been buried by answers, the research is oriented as a phenomenographic inquiry. This mode of inquiry seeks to describe, analyse, and understand the qualitatively different experiences 1yr teachers undergo in their identity formation and transformation. The results of this research reveal that beginning teachers’ identity transformation through their first experiences have both individual features specific to each teacher’s roles and aspirations, and extra-individual factors such as interactions, affiliations, and status, which shape their identity. Categories of description that have emerged from the analysis include survival, liminal, and hegemonic discourses, artifacts as symbols of belonging, and the impact of the contractual nature of teaching. Implications of this research focus on the importance for beginning teachers to develop an understanding of the transformative nature of identity in relation to the practice of teaching, to counter the negative preconceptions beginning teachers are told to expect as rites of passage upon entering the profession. The research outcomes have implications for teacher educators and in-service teachers negotiating the waters of an ever-changing profession.