On the nature of short-range growth inhibition in juvenile lobsters (Homarus)

By means of compartmental analysis of two experiments manipulating flow rate, short-range density-dependent growth inhibition in juvenile lobsters (Homarus) was shown to implicate a rapidlydecaying or ephemeral substance. Pulsed production of a long-lived inhibitor was ruled out as a sole explanation of the effect. Behavioral observations eliminated the hypothesis that reduced growth of inhibited animals was causally related to their increased locomotory activity. Implications for chemical ecology of the effects of ephemeral agents upon growth and behavior are discussed.     

Hydrogen Peroxide Stimulates Activity and Alters Behavior in Drosophila melanogaster

Circadian rhythms in animals are regulated at the level of individual cells and by systemic signaling to coordinate the activities of multiple tissues. The circadian pacemakers have several physiological outputs, including daily locomotor rhythms. Several redox-active compounds have been found to function in regulation of circadian rhythms in cells, however, how particular compounds might be involved in regulating specific animal behaviors remains largely unknown. Here the effects of hydrogen peroxide on Drosophila movement were analyzed using a recently developed three-dimensional real-time multiple fly tracking assay. Both hydrogen peroxide feeding and direct injection of hydrogen peroxide caused increased adult fly locomotor activity. Continuous treatment with hydrogen peroxide also suppressed daily locomotor rhythms. Conditional over-expression of the hydrogen peroxide-producing enzyme superoxide dismutase (SOD) also increased fly activity and altered the patterns of locomotor activity across days and weeks. The real-time fly tracking system allowed for detailed analysis of the effects of these manipulations on behavior. For example, both hydrogen peroxide feeding and SOD over-expression increased all fly motion parameters, however, hydrogen peroxide feeding caused relatively more erratic movement, whereas SOD over-expression produced relatively faster-moving flies. Taken together, the data demonstrate that hydrogen peroxide has dramatic effects on fly movement and daily locomotor rhythms, and implicate hydrogen peroxide in the normal control of these processes.     

Incorporating Natural Variability into the Assessment of Ecological Health in Australian Dryland Rivers

Dryland rivers occur over much of Australia’s inland and have some of the most variable patterns of flow in the world. Despite their dominance in terms of Australia’s river types, dryland rivers have not been the focus of the recent increase in research on indicators of river health, mostly owing to their spatial remoteness and relatively low levels of water resource development and human disturbance. Most rivers in arid and semi-arid regions are ephemeral, and only carry significant flows during the wetter months or following infrequent but intense rainfall events. It is not known which, if any, of the existing approaches to river health assessment can be used to accurately assess the health of these large ephemeral rivers. This paper considers why the standard methods for interpreting the currently-used indicators for river health may need to be adapted for variable systems and suggests the use of trends that recognise natural variation in indicator values for undertaking this.     

Shown but not Shared,Presented but not Proffered: Redefining Ritual Identity among Warlpiri Ritual Performers, 1990–2000

Little has been written on the construction and projection of indigenous social identity in public (‘non‐restricted’) ritual among Aboriginal Australians. Elsewhere, I have analysed nearly half a century of such public rituals (1946–1990) among the Warlpiri of Yuendumu in Central Australia, concentrating on the shifting forces of gender and kinship. This paper focuses on the key moments motivating senior Warlpiri women, since the 1990s, to reconfigure their ritual participation and roles in inter‐indigenous ceremonial events. I analyse how these women participate in inter‐Aboriginal performances, exhibiting the iconic and sensory virtues of the Dreaming and weaving new forms of political identity, shaped by the pressures of neo‐colonialism, with female ambassadors of other Aboriginal groups. I argue that in this performative process women are reconfiguring the meanings of Aboriginalities and rearticulating their connectedness to one another, a connectedness rooted in their beliefs and responsibilities towards the Dreaming.     

Circadian organization of running-wheel activity, food intake and drinking of old male rats

Circadian rhythms of running-wheel activity, food intake and drinking were monitored in old male rats of Long-Evans strain over 22 months of age in both entrained (light:dark 12:12, LD) and free running condition (continuous illumination, LL) and were compared with those of young adult male rats of 3.5 to 6.5 months of age. Twenty-four hour distribution of running activity, feeding events and licking events of young rats as well as old rats showed bi- or tri-modal patterns during the 12 hr dark period of the LD schedule. In the light period, 2 out of 8 old rats, 6 out of 10 old rats and 1 out of 6 old rats had 1 or 2 medium or high peaks in running activity, feeding events and licking events, respectively, leading to equal distribution between the dark and light period. In the LD schedule, old rats showed a decrease in running-wheel activity, its patterns and power spectra, a decrease in feeding events and its power spectra in 6 rats which lost circadian rhythms and increase in feeding events and its power spectra in 4 rats which still showed circadian rhythms and increase in licking events. LL suppressed running-wheel activity, its patterns and power spectra, licking events and its power spectra and feeding events in young rats. However, LL could suppress only feeding events of 4 rats which still showed circadian rhythms and licking events and its spectral level in old rats. The possible causes of decreased response to LL in old rats and its implication are discussed.     

The Goldilocks effect: intermittent streams sustain more plant species than those with perennial or ephemeral flow

1. Drylands worldwide are typified by extreme variability in hydrologic processes, which structures riparian communities at various temporal and spatial scales. One key question is how underlying differences in hydrology over the length of interrupted perennial rivers influence spatial and temporal patterns in species richness and species composition. 2. We examined effects of differences in dry season hydrology on species richness, composition and cover of herbaceous plant communities in the streamside zone (the zone influenced directly by low flows in the channel). Data were collected at ephemeral, intermittent and perennial flow reaches on three rivers of the desert Southwest (Arizona, U.S.A.): Lower Cienega Creek, Hassayampa River and Lower San Pedro River. 3. Patterns of species richness varied with temporal scale of analysis, that is between single‐year and multi‐year time frames. At the annual timescale, quadrat species richness (m^?2) and herbaceous cover were higher at sites with perennial flow than at either intermittent or ephemeral sites. In contrast to this single‐year pattern, the highest long‐term richness occurred at intermittent sites. 4. Quadrat species richness, total species richness at a site (per 18 1‐m² plots) and cover were more variable year to year at non‐perennial sites than at perennial flow sites. On two of the three rivers, ephemeral sites had the highest inter‐annual compositional variance, while the perennial sites had the lowest. 5. Compositional differences between the hydrologic site types were dominated by species turnover, not nestedness. The perennial sites had more wetland and perennial species than the other two site types. The intermittent sites had more annual species than did the other two types. 6. High long‐term species richness and distinct species composition of intermittent sites are probably sustained by pronounced temporal variability in environmental conditions (i.e. frequent and persistent flow events, and dry periods). Plants at these sites take advantage of greater moisture than those at ephemeral sites and also experience less competition from resident species than those at perennial sites. 7. Conservation of desert riparian diversity depends upon the protection of consistently wet conditions at perennial flow sites, as well as the maintenance of the processes that cause fluctuations in environmental conditions at non‐perennial sites.     

Sickening Bodies: How Racism and Essentialism Feature in Aboriginal Women's Discourse about Health1

In the last decade there has been much interest in the concepts of ‘racism’ and ‘essentialism’ and the ways in which these notions have been appropriated by Aboriginal people to demarcate a specifically Aboriginal space (Cowlishaw 1986; Lattas 1993; Langton 1981; Morris 1988; Muecke 1992). Central to these concerns is the issue of black/white relations and the specificities of racial oppression. Following these concerns in this article I explore the nexus between the metaphorical dismemberment of self and the corporeal dismemberment of sickness which is reflected in the high mortality rates and disease patterns of Aboriginal people. I extend Fanon's concept that racism has the power to alienate ‘a man of colour’ from his own self-image to argue that it more than metaphorically breaks the human body (Fanon 1991). I provide a window into a much neglected area of research: how notions of illness and social relatedness are constructed in particular socio-historical circumstances. I explore the meanings of illness as expressed at the level of community and as a form of embodiment associated with unequal colonial relations. I focus on indigenous exegeses which articulate Aboriginal women's experience of illness and their sense of identity. I draw on the work of Leder (1990) to foreground a phenomenological view where selfhood is continually confronted by circumstances that make present the ‘body’ as a ‘sharp and searing presence threatening the self’. I also apply Sansom's (1982) model of illness and the significance of carers in an Aboriginal community to demonstrate a world-view of personhood that is diffused with other persons and things rather than a world-view that entails a highly individuated and bounded self. In this world-view adequate healing requires a reconstitution of social relations and a re-ordering of the racialised status quo.     

Living where the flow is right: How flow affects feeding in bryozoans

Bryozoans are suspension feeding colonial animals that remain attached to the substratum or other surfaces. How well a bryozoan can feed in a particular flow regime could help determine the distribution and abundance of that bryozoan. I tested how velocity of flow affects feeding rate in four species of bryozoans in the laboratory and how these species perform in different flow regimes in the field. I found that one species, Membranipora membranacea, had a higher ingestion rate than did the other three species at all velocities of flow tested. Membranipora also had a higher rate of ingestion at intermediate velocities, while velocity did not have as strong an effect on ingestion rate in the other three species. As predicted from the feeding experiments, all four species generally had greater abundance, attained a larger size, grew faster, and survived longer in flow regimes in which feeding is higher. Also as predicted, Membranipora had greater abundance, attained a larger size, grew faster, and survived longer than did the other three species both in slower and faster flow regimes in the field. Understanding how flow affects feeding can help predict the distribution and abundance of bryozoans in the field. Because especially efficient filterers like Membranipora can grow faster and have higher survival under a wide range of conditions of flow, this species may be able to outcompete many other species or take advantage of ephemeral habitats, thereby becoming a potentially effective invasive species as has been seen in the Gulf of Maine.     

Actin restricts FcepsilonRI diffusion and facilitates antigen-induced receptor immobilization

The actin cytoskeleton has been implicated in restricting diffusion of plasma membrane components. Here, simultaneous observations of quantum dot-labelled FcepsilonRI motion and GFP-tagged actin dynamics provide direct evidence that actin filament bundles define micron-sized domains that confine mobile receptors. Dynamic reorganization of actin structures occurs over seconds, making the location and dimensions of actin-defined domains time-dependent. Multiple FcepsilonRI often maintain extended close proximity without detectable correlated motion, suggesting that they are co-confined within membrane domains. FcepsilonRI signalling is activated by crosslinking with multivalent antigen. We show that receptors become immobilized within seconds of crosslinking. Disruption of the actin cytoskeleton results in delayed immobilization kinetics and increased diffusion of crosslinked clusters. These results implicate actin in membrane partitioning that not only restricts diffusion of membrane proteins, but also dynamically influences their long-range mobility, sequestration and response to ligand binding.     

ADAPTIVE COLORATION AND GENE FLOW AS A CONSTRAINT TO LOCAL ADAPTATION IN THE STREAMSIDE SALAMANDER,AMBYSTOMA BARBOURI

Predation is an important selective force that influences animal color patterns. Some larval populations of the streamside salamander, Ambystoma barbouri, inhabit streams with fish predators. Other larval salamanders are found in shallow, ephemeral streams that are predator-free. Quantitative melanophore cell counts and estimates of percent body area pigmented indicated that larval coloration is strongly correlated with stream type. Larvae that coexist with fish tend to be lighter than larvae from streams that are Ashless and ephemeral. Two approaches demonstrated that lightly pigmented salamander larvae better match the common background in relatively permanent streams and are less conspicuous to fish than dark larvae. First, using a model based on the spectral sensitivity of the fish and reflectance properties of salamanders and natural stream backgrounds, we showed that light larvae are three times more cryptic than dark larvae on rocks. Second, lighter larvae had higher survival than darker salamanders on rocks in a predator- choice experiment. It is not clear why larvae in ephemeral streams are darker. Larvae in ephemeral streams should be active to feed and develop rapidly and reach sufficient size to metamorphose before seasonal drying. Several hypotheses may explain why larvae tend to be darker in ephemeral streams, such as increased thermoregulatory ability, better screening of ultraviolet radiation (in these shallower streams), or better background matching to terrestrial predators. Among populations where salamander larvae coexist with fish, there are differences in relative crypsis. Larvae from populations with fish and relatively high gene flow from ephemeral populations (where larvae are dark) tend to be darker (with more melanophores) and more conspicuous to predators than those from more genetically isolated populations, where larvae are lighter and more cryptic. These differences illustrate the role of gene flow as a constraint to adaptive evolution.     

Circadian and Ultradian Rhythms in Blood Glucose and Plasma Insulin of Healthy Adults

The circadian and ultradian variations of blood glucose and plasma insulin have been characterized individually and as a group phenomenon in five healthy young adults studied while adhering as closely as possible to their usual routine of sleep, activity, meal content and timing. Three complementary methods were used to analyze the data: displaying raw data as a function of time; cosinor method according to Nelson and Halberg; and time series analyses as proposed by De Prins and Malbecq. The subjects were studied in the laboratory and their life routine were controlled, but very close to that of their habitual routine. They had mainly ultradian rhythms of blood glucose (mainly about 6 hr) and circadian rhythms of immunoreactive insulin (I.R.I.). Blood glucose ultradian rhythms seem to be mainly but not exclusively mealtime dependent, while I.R.I, circadian rhythms appear to be primarily endogenous in origin. Therefore, the role played by insulin in the control of blood glucose levels seems to be programmed on a circadian basis rather than by a time independent feedback phenomenon as postulated by the conventional homeostatic hypothesis. The advantage of this chronophysiologic approach is to consider circadian rhythms of both I.R.I. and insulin effectiveness as an adaptive phenomenon able to maintain blood sugar changes in the ultradian domain of rhythms.     

What Makes a Fly Enter Diapause?

Diapause is a dormant state that insects may undergo as a response to changing environmental conditions. In flies, like many insects inhabiting temperate zones, diapause occurs generally during the winter months when ambient temperatures are cool and food sources scarce. Whilst the environmental factors involved in determining diapause have been known for a long time, the genes and molecular events controlling its initiation are poorly understood. Here I outline the factors that initiate diapause and highlight recent studies that implicate insulin signaling in its control.     

What makes a fly enter diapause?

Diapause is a dormant state that insects may undergo as a response to changing environmental conditions. In flies, like many insects inhabiting temperate zones, diapause occurs generally during the winter months when ambient temperatures are cool and food sources scarce. Whilst the environmental factors involved in determining diapause have been known for a long time, the genes and molecular events controling its initiation are poorly understood. Here I outline the factors that initiate diapause and highlight recent studies that implicate insulin signaling in its control.     

Effects of pattern element density upon displacement limits for motion detection in random binary luminance patterns.

The upper motion displacement threshold (Dmax) was determined with two-frame motion sequences of random binary luminance patterns, over a range of pattern element sizes and densities. Dmax was little affected by density at small element sizes (less than 5 arcmin), in agreement with previous reports. However, at larger element sizes (greater than 9 arcmin) Dmax increased as element density was reduced in the range 50-5%. We explain our findings by a model which takes into account spatial-frequency filtering prior to motion detection, and the effects of pattern density upon the statistics of random binary patterns. We also implicate the dependence of Dmax upon the contrast energy of the elements in broadband patterns, and provide a direct demonstration that Dmax is contrast limited over a wide range of pattern contrasts (72-2.5%). Previous reports that Dmax is independent of density should be modified to take into account the complex effects of density upon the statistics of random patterns, and the existence of physiological filtering prior to motion detection.     

Are Chironomidae (Diptera) good indicators of water scarcity? Dryland streams as a case study

Water scarcity is becoming one of the greatest challenges that human societies will face during this century. Monitoring water availability is expensive and technically challenging. In this regard, biological communities (e.g. aquatic insects) offer a cost-effective alternative, since they integrate temporal and spatial hydrological variability.Here we explore the potential of Chironomidae (Diptera), which have been usually neglected due to their complex taxonomy, as indicators of both local habitat condition and water scarcity. The study took place in 28 sites across seven dryland streams distributed within a 400 km² section of the Upper San Pedro River basin, southeastern Arizona. The selected streams covered a wide range of hydrological variability, which was continuously measured through the deployment of 15 electrical resistance (ER) sensors. Chironomidae taxa with no drought-resistance strategies were rarely found in streams that experienced frequent drying events (i.e. intermittent and ephemeral streams), suggesting that droughts have the potential to reduce species richness due to local extinctions of drought-intolerant taxa. Intermittent and ephemeral streams registered low canopy cover and a significantly higher abundance of scrapers (which mainly feed on algae) and shredders (feeding on poorly decomposed coarse organic material). This suggests that structural changes associated to drought (e.g. reduced canopy cover and decomposition rates) might lead to changes in the functional composition of the Chironomidae assemblages. We conclude that Chironomidae species can be used as indicators of hydrological variability and the impacts of drought on streams in the absence of flow gauges.     

New Genetic and Linguistic Analyses Show Ancient Human Influence on Baobab Evolution and Distribution in Australia

This study investigates the role of human agency in the gene flow and geographical distribution of the Australian baobab, Adansonia gregorii. The genus Adansonia is a charismatic tree endemic to Africa, Madagascar, and northwest Australia that has long been valued by humans for its multiple uses. The distribution of genetic variation in baobabs in Africa has been partially attributed to human-mediated dispersal over millennia, but this relationship has never been investigated for the Australian species. We combined genetic and linguistic data to analyse geographic patterns of gene flow and movement of word-forms for A. gregorii in the Aboriginal languages of northwest Australia. Comprehensive assessment of genetic diversity showed weak geographic structure and high gene flow. Of potential dispersal vectors, humans were identified as most likely to have enabled gene flow across biogeographic barriers in northwest Australia. Genetic-linguistic analysis demonstrated congruence of gene flow patterns and directional movement of Aboriginal loanwords for A. gregorii. These findings, along with previous archaeobotanical evidence from the Late Pleistocene and Holocene, suggest that ancient humans significantly influenced the geographic distribution of Adansonia in northwest Australia.     

饲养状态真鲂(鱼弗)发声的昼夜与季节变化

本文研究了受水温和光周期等自然变化影响的饲养状态真鲂鮄发声的昼夜与季节变化,并研究了实验鱼活动(鱼类游泳次数)的日变化。声音信号的昼夜节律记录发声活动的日常水平(摄食之外的时期),但是每月变化的记录(季节性式型)则在摄食期间进行,因为摄食时声音信号增加,而日常发声活动较不频繁。实验鱼包括雌雄两性,且未达性成熟。真鲂鮄在白天发声多一些,也更活跃。声音为阵发式的,较不频繁(平均值=0.04发声/min每鱼每天)。最少的发声活动出现在晚上,凌晨和黄昏居中(声音的阵发更频繁,但是声音更少),最多的发声活动出现在白天(声音的阵发更频繁,并且含更多数目的声音)。竞争摄食时声音信号的比率不呈现季节性变化(平均值=3.98发声/min每鱼),与温度也不相关,显示出竞争摄食时声音的发出以最大比率进行。敲击声和呼噜声的某些声学特征与温度相关,特别是在较高的温度下呼噜声的节拍间隔急剧下降。敲击声和呼噜声的声音参数中的季节性变化,多数可以解释为发声肌肉和中央声音控制回路的温度效应。