Variation in the dispersal potential of non-feeding invertebrate larvae: the desperate larva hypothesis and larval size

For many species of marine invertebrates, variability in larval settlement behaviour appears to be the rule rather than the exception. This variability has the potential to affect larval dispersal, because settlement behaviour will influence the length of time larvae are in the plankton. Despite the ubiquity and importance of this variability, relatively few sources of variation in larval settlement behaviour have been identified. One important factor that can affect larval settlement behaviour is the nutritional state of larvae. Non-feeding larvae often become less discriminating in their 'choice' of settlement substrate, i.e. more desperate to settle, when energetic reserves run low. We tested whether variation in larval size (and presumably in nutritional reserves) also affects the settlement behaviour of 3 species of colonial marine invertebrate larvae, the bryozoans Bugula neritina and Watersipora subtorquata and the ascidian Diplosoma listerianum. For all 3 species, larger larvae delayed settlement for longer in the absence of settlement cues, and settlement of Bugula neritina larvae was accelerated by the presence of settlement cues, independently of larval size. In the field, larger W subtorquata larvae also took longer to settle than smaller larvae and were more discriminating towards settlement surfaces. These differences in settlement time are likely to result in differences in the distance that larvae disperse in the field. We suggest that species that produce non-feeding larvae can affect the dispersal potential of their offspring by manipulating larval size and thus larval desperation.

The ambivalent practices of reflexivity

Reflexivity involves turning one's reflexive gaze oil discourse-turning language back on itself to see the Work it does in constituting the world. The subject/researcher sees simultaneously the object of her or his gaze and the means by which the object (which may include oneself as subject) is being constituted. The consciousness of self that reflexive writing sometimes entails may be seen to slip inadvertently into constituting the very (real) self that seems to contradict a focus on the constitutive power of discourse. This article explores this site of slippage and of ambivalence. In a collective biography oil the topic of reflexivity, the authors tell and write stories about reflexivity and in a doubled reflexive arc, examine themselves at work during the workshop. Examining their own memories and reflexive practices, they explore this place of slippage and provide theoretical and practical insight into what is going on in reflexive research and writing.

An archaeobotanical perspective on Holocene plant-use practices in lowland northern New Guinea

Existing archaeobotanical and palynological records of plant use in the northern New Guinea lowlands are reviewed in light of recent work at Kuk and theoretical refocusing on plant use practice. A practice-based approach is supported as the most useful way of investigating the highly problematical area of tropical plant food production. The existing direct record of past plant use in lowland New Guinea is considered woefully inadequate to achieve this task, as is that in Near Oceania and Island Southeast Asia. Archaeobotanical methods exist to fill the void, but full implementation requires a change in general archaeological and palaeoecological practice.

Labour flexibility and gender in the service sector: A study of employment practices in law and accounting firms

In seeking to increase the flexibility of their use of employee time, employers can pursue strategies based on the employment of casual and part-time workers (numerical flexibility) or strategies based on ad hoc variation of the working hours of permanent employees (working time flexibility). Patterns of flexibility strategies and their implications are examined in the context of a highly feminised sector of work-clerical and administrative employment in law and accounting firms. We consider whether, as is often assumed, working time flexibility strategies are generally better for employees because they avoid the substitution of core, high quality jobs with the peripheral, relatively insecure employment often associated with casualisation. Analysing data drawn from a survey of law and accounting firms, we argue that there are three distinct flexibility strategies adopted by employers, and that the choice of strategy is influenced by the size of the firm and the extent of feminisation. The quality of employment conditions associated with each strategy is investigated through an analysis of the determinants of training provision for clerical and administrative workers. Rather than an expected simple linear relationship between increasing casualisation and decreasing training provision, we find that firm size and feminisation are implicated. Larger firms that tend to employ at least some men and use a combination of working time and numerical flexibility strategies tend to provide more training than the small, more fully feminised firms that tend to opt for either casualisation or working time flexibility strategies. This suggests that, from an employee perspective, working time flexibility may not be as benevolent as is often thought.

Searching behaviour and diet of Oystercatcher Haematopus ostralegus pairs feeding in their territories

Search path, searching behaviour and diet of pairs of Oystercatchers feeding in mudflat territories were studied during spring. females ate Nereis, Mya, small unidentified prey, probably Corophium, and a few Macoma, whereas males primarily ate Macoma. Even when female and male foraged in the same site, they often caught different prey. The combination of 'The Search-rate/Detection Model' (Gendron & Staddon 1983) and 'The Harvestable Prey Model' (Zwarts & Wanink 1993) provide the theoretical framework in which to explain these differences in diet. Macoma are thought to be more cryptic than Nereis, Mya and Corophium. Therefore females, while searching at a faster rate than their respective mates, caught far fewer cryptic prey, but a greater number of more conspicuous prey than their mates. On the basis of distances moved before and after capturing prey, males exhibited area-restricted searching for Macoma and Corophium. In contrast, females did not exhibit any area-restricted searching. it is suggested that the distribution of Macoma and Corophium available to males searching slowly was more clumped than that of these two prey species available to females searching more quickly.

Survey of countertrade practices in Australia

This empirical exploratory study is part of a larger comprehensive study of countertrade practices in the Asia-Pacific region. A mail survey of 600 Australian international trading firms reveals that a positive attitude toward countertrade exists among both countertraders and non-countertraders in Australia. Further the study reveals the major motivating factors, the benefits derived difficulties faced and reasons for not countertrading by Australian firms. In addition, the study identifies the forms of countertrade used, the countries sewed, and the product and service categories countertraded. The results are compared to earlier studies of UK and Canadian firms, and the implications for international marketing managers are discussed. (C) Elsevier Science Inc., 1997.

Ethanol feeding enhances inflammatory cytokine expression in lipopolysaccharide-induced hepatitis

Elevated concentrations of plasma tumour necrosis factor (TNF)-alpha, interleukin (IL)-1 and IL-6 have been detected in patients with alcoholic hepatitis and have been implicated in the pathogenesis of hepatocyte necrosis. The present study used a rat model to conduct a detailed histological and biochemical examination of the expression of various pro-inflammatory cytokines and associated liver pathology in ethanol-potentiated lipopolysaccharide (LPS)-induced liver injury. Male Wistar rats were pair-fed either the control or ethanol-containing (36% of caloric intake as ethanol) form of the Lieber-DeCarli liquid diet for 6 weeks. Liver injury was induced by the i.v. injection of LPS (1 mu g/g bodyweight), with animals being killed at O, 1, 3, 6, 12 and 24 h after injection. At the later time points, plasma transaminase and transpeptidase activities were significantly elevated in ethanol-fed LPS-treated rats compared with control-fed LPS-treated animals. At these times after LPS treatment, hepatocytes in ethanol-fed animals displayed fatty change and necrosis with an associated neutrophil polymorph infiltrate. Time course analysis revealed that plasma TNF-alpha (1-3 h post-LPS) and IL-6 (3 h post-LPS) bioactivity was significantly elevated in ethanol-fed compared with control-fed animals. No difference was seen in plasma IL-1 alpha concentration (maximal in both groups 6 h post-LPS). The expression of TNF-alpha, IL-1 alpha, IL-1 beta and IL-6 mRNA were elevated between 1 and 6 h post-LPS in the livers of both control and ethanol-fed rats. However, ethanol-fed LPS-treated animals exhibited significantly higher maximal expression of IL-1 and IL-6 mRNA. Comparison of the appearance of cytokine mRNA and plasma bioactivity indicated an effect of ethanol feeding on post-transcriptional processing and/or the kinetics of the circulating cytokines. Elevated levels of both hepatic cytokine mRNA expression and the preceding plasma cytokines are presumably a necessary prerequisite for hepatic injury seen in this model and, therefore, possibly for the damage seen in human alcoholics. Further studies using this model may lead to significant advances in our understanding of the pathogenic mechanisms of alcoholic liver disease in humans.