Synchronization by low-amplitude light-dark cycles of 24-hour pineal and plasma melatonin rhythms of hatchling European starlings (Sturnus vulgaris)

In young European starlings, as in other avian species, high-amplitude 24-hr rhythms in plasma and pineal melatonin are already present around the time of hatching. In chickens this rhythmicity results at least partly from the light sensitivity of the melatonin-producing and -secreting system. In contrast to the chicken, the starling is a hole-nesting bird, and it seemed questionable whether the low light intensities in the nest are sufficient to synchronize perinatal melatonin rhythms. We therefore exposed starling eggs to light cycles roughly simulating those measured in nest-boxes, i.e., an 11-hr phase of complete darkness and a 13-hr phase consisting of 15 min of dim light (10 lux) alternating with 30 min of darkness. For one group the photophase lasted from 0600 to 1900 hr; for the other group the photophase lasted from 1800 to 0700 hr. In approximately 10-hr-old hatchlings of both groups, plasma and pineal melatonin concentrations were high during the dark phase and low during the light phase. We conclude that perinatal low-amplitude light intensity changes of the kind experienced by hatching starlings in the field are sufficient for synchronizing the melatonin-producing and -secreting system in the pineal and possibly other organs.

Foraging behaviour and habitat selection of the little penguin Eudyptula minor during early chick rearing in Bass Strait, Australia

Knowledge of the foraging areas of top marine predators and the factors influencing them is central to understanding how their populations respond to environmental variability. While there is a large body of literature documenting the association of air-breathing marine vertebrates with areas of high marine productivity, there is relatively little information for species restricted to near-shore or continental-shelf areas. Differences in foraging range and diving behaviour of the little penguin Eudyptula minor were examined from 3 breeding colonies (Rabbit Island, Kanowna Island and Phillip Island) in central northern Bass Strait, southeast Australia, during the chick-guard stage using electronic tags (platform terminal transmitters, PTTs, and time-depth recorders, TDRs). Although there were large overall differences between individuals, the mean maximum foraging range (16.9 to 19.8 km) and mean total distance travelled (41.8 to 48.0 km) were similar between the 3 colonies, despite different bathymetric environments. Individuals from all 3 colonies selected foraging habitats within a narrow sea surface temperature (SST) range (16.0 to 16.4°C). While there were significant differences in mean dive depths (5.4 to 10.9 m) and mean durations (13.2 to 28.6 s) between the different colonies, the mean diving effort (vertical distance travelled: 936.3 to 964.3 m h–1) was similar. These findings suggest little penguins from the 3 colonies employ relatively similar foraging efforts yet are plastic in their foraging behaviours.

Diet of common diving-petrels (Pelecanoides Urinatrix Urinatrix) in Southeastern Australia during chick rearing

Unlike conspecifics in the subantarctic region, which typically begin breeding in mid-spring to summer, Common Diving-petrels Pelecanoides urinatrix urinatrix in southeastern Australia (towards the northern limit of the species' distribution) commence breeding mid winter. Knowledge of the foraging ecology of this species is crucial to understanding the factors that influence its timing of breeding in the region, yet there is currently little information available. Analysis of 43 stomachs of breeding adults, collected opportunistically after they were killed in a fire which burned through their colony, indicated that their diet was dominated by two taxa: a euphausiid Nyctiphanes australis which comprised 87% of the diet by number; and a hyperiid amphipod Themisto australis which constituted a further 12.5%. Mean lengths (±SE) of N. australis (n = 39) and T. australis (n = 41) were 12 mm (±0.3) and 5.2 mm (±0.2), respectively. The importance of N. australis in the diet of Common Diving-petrels is discussed in relation to their timing of breeding and the euphausiid's potential role in the Bass Strait pelagic ecosystem.

Doing what your big sister does : sex, postfeminism and the YA chick lit series

Mass-marketed teen chick lit has become a publishing phenomenon and has begun to attract critical interest among children’s literature scholars. Much of this critical work, however, has shied away from robust critical assessment of the postfeminist conditions informing the production and reception of young adult series like Private, Gossip Girl and Choose Your Own Destiny. Existing analyses may nod to the origins of the genre in women’s chick lit, but do not investigate how the postfeminist construction of ‘empowered’ female (hetero) sexuality translates into chick lit for young adults. Paying particular attention to these issues, this paper draws on feminist critiques of postfeminism to interrogate the implications of the way these novels position readers to understand their sexuality. In doing so, it poses postfeminist criticism as an unconsidered yet significant framework to evaluate novels for teenage girls.

Maternal transfer of mercury to the developing embryo/fetus : is there a safe level?

Mercury (Hg) exposure is ubiquitous in modern society via vaccines, fish/crustacea, dental amalgam, food, water, and the atmosphere. This article examines Hg exposure in the context of primary exposure to pregnant women and secondary exposure experienced by their unborn babies. Babies in utero are particularly at risk of higher Hg exposure than adults (on a dose/weight basis through maternal Hg transfer via the placenta), and are more susceptible to adverse effects from mercury and its biologically active compounds. It is, therefore, critical that regulatory advisories around maximum safe Hg exposures account for pregnant women and secondary exposure that children in utero experience. This study focused on standardized embryonic and fetal Hg exposures via primary exposure to the pregnant mother of two common Hg sources (dietary fish and parenteral vaccines). Data demonstrated that Hg exposures, particularly during the first trimester of pregnancy, at well-established dose/weight ratios produced severe damage to humans including death. In light of research suggestive of a mercuric risk factor for childhood conditions such as tic disorders, cerebral palsy, and autism, it is essential that Hg advisories account for secondary prenatal human exposures.

The M4 muscarinic antagonist MT-3 inhibits myopia in chick: evidence for site of action

It is well established that the broad-band muscarinic antagonist, atropine is effective at inhibiting the progression of myopia and does so by preventing the elongation of the vitreous chamber of the eye. However, uncertainty remains as to whether this effect occurs through a receptoral mechanism and, if so, which muscarinic receptor subtype mediates this effect. Previous work, in avian and mammalian models of myopia, implicates the M1 and M4 receptors as potential targets. The current study used physiologically relevant concentrations of highly selective muscarinic antagonists (MT-3 and MT-7) to further characterise the role of the M4 receptor in the control of myopia in the chick model of refractive development.

Inhibition of matrix metalloproteinase activity in the chick sclera and its effect on myopia development

To investigate the contribution of matrix degradation in the two-layer avian sclera to the development of myopia. Tissue inhibitor of metalloproteinase-2 (TIMP-2) was used to inhibit chick scleral collagen degradation with (3)H-proline, a marker for this effect. Ex vivo scleral culture experiments confirmed TIMP-2 doses for in vivo experimentation. Ocular growth and refractive response to exogenous TIMP-2 (11.25, 2.25, and 0.45 picomoles, plus vehicle only) were monitored in 7-day-old chicks during the induction of myopia over 4 days with a translucent occluder. Collagen degradation was assessed, in whole sclera and in separated scleral layers by using the same paradigm (11.25 picomoles TIMP-2; vehicle only).Approximately 60% of collagen degradation was inhibited with low (2 nM) doses of TIMP-2 in the ex vivo sclera. Degradative activity in the in vivo chick sclera increased significantly (46%) during myopia development, with all the altered activity confined to the fibrous layer. Addition of TIMP-2 significantly reduced (by 46%) this accelerated scleral collagen degradation, also by acting in the fibrous layer. TIMP-2 had no significant effect on (3)H-proline incorporated in the cartilaginous scleral layer and cornea. Despite inhibiting collagen degradation TIMP-2 had no significant effect on myopia development. Increased collagen degradation is a feature of scleral remodeling in chick myopia development, but is confined to the fibrous scleral layer. Significant inhibition of this collagenolytic activity with TIMP-2 has little effect on refractive error development, suggesting that collagen degradation in the sclera contributes little to the development of myopia in the chick.

Urea-based osmoregulation in the developing embryo of oviparous cartilaginous fish (Callorhinchus milii) : contribution of the extraembryonic yolk sac during the early developmental period

Marine cartilaginous fish retain a high concentration of urea to maintain the plasma slightly hyperosmotic to the surrounding seawater. In adult fish, urea is produced by hepatic and extrahepatic ornithine urea cycles (OUCs). However, little is known about the urea retention mechanism in developing cartilaginous fish embryos. In order to address the question as to the mechanism of urea-based osmoregulation in developing embryos, the present study examined the gene expression profiles of OUC enzymes in oviparous holocephalan elephant fish (Callorhinchus milii) embryos. We found that the yolk sac membrane (YSM) makes an important contribution to the ureosmotic strategy of the early embryonic period. The expression of OUC enzyme genes was detectable in the embryonic body from at least stage 28, and increased markedly during development to hatching, which is most probably due to growth of the liver. During the early developmental period, however, the expression of OUC enzyme genes was not prominent in the embryonic body. Meanwhile, we found that the mRNA expression of OUC enzymes was detected in the extra-embryonic YSM; the mRNA expression of cmcpsIII in the YSM was much higher than that in the embryonic body during stages 28-31. Significant levels of enzyme activity and the existence of mitochondrial-type cmgs1 transcripts in the YSM supported the mRNA findings. We also found that the cmcpsIII transcript is localized in the vascularized inner layer of the YSM. Taken together, our findings demonstrate for the first time that the YSM is involved in urea-based osmoregulation during the early to mid phase of development in oviparous cartilaginous fish.

Little penguin Eudyptula minor at Middle Island, Western Victoria : current status

We examined the status of the Little Penguin Eudyptula minor at Middle Island on the west coast of Victoria during the species' 1999/2000 breeding season. The vegetated upper surface of the island had 292 occupied burrows at a density of 0.02/m². Peak dusk arrival occurred in January with 502 penguins coming ashore during a one-hour period. Little Penguins at Middle Island displayed important differences in breeding ecology from penguins in other Australian colonies. Early breeding combined with heavier adult and chick weights resulted in high breeding success. However, as Middle Island is a popular destination for day visitors, during the 1999/2000 Little Penguin breeding season, tourism ·was found to cause detrimental effects, including deaths of some eggs and chicks. There are also concerns for the conservation of the Little Penguin colony as faxes or dogs may readily access the island.

The breeding biology of the White-faced Storm Petrel (Pelagodroma marina) on Mud Islands, Port Phillip Bay, Victoria

The White-faced Storm Petrel (Pelagodroma marina) is restricted to three breeding colonies within Victoria: Mud Islands and South Channel Fort in Port Phillip Bay, and Tullaberga Island off Mallacoota. Numbers of these storm petrels breeding on Mud Islands have declined considerably since early last century. White-faced Storm Petrels were recorded on Mud Islands from early September 2002 until mid-March 2003 when the last chicks fledged. Eggs were laid from late October to early December, with chicks hatching in the later half of December. The mean incubation period was 51.7 days (± 3.2 days (s.d.), range = 38–53, n = 13), and may have been extended by periods of egg neglect. The mean nestling period was 54.8 days (± 4.4 days (s.d.), range 50–70, n = 21). Chick growth is described. Hatching success was 54% and fledging success was 77.8%, with overall breeding success being 42%. Burrow densities were found to be influenced by plant species, vegetation height and soil moisture. The position of the burrow within the colony was shown to influence breeding success, with those nearer the edge of the storm petrel colony, closer to the marsh, and further from a colony of Australian White (Threskiornis molucca) and Straw-necked (T. spinicollis) Ibis recording higher success.

Consolidating one novel structure whilst constructing two more

This study reports the cognitive processing of a Year 8 female student (Kerri) during a test, and during her subsequent homework as she consolidated as part of abstracting; a topic of recent research interest. This case adds to the body of knowledge about how constructing and consolidating can occur simultaneously. The analysis captured the complexity of the cognitive processing, and their intertwined nature. Data was captured through lesson video, and post-lesson, video-stimulated reconstructive student interviews. It was found that Kerri’s constructing and consolidating included characteristics previously identified by others, and an additional feature. Her constructing included “branching” (Kidron & Dreyfus, 2004, p. 159); but unlike the case cited, one of these branches related to a new goal.