Sperm environment affects offspring quality in broadcast spawning marine invertebrates

The provisioning of offspring can have far-reaching consequences for later life in a wide range of organisms and generally this provisioning is thought to be under maternal influence or control. In experiments with a broadcast-spawning ascidian, we found that the size of offspring was determined by egg size and the abundance of sperm present during fertilization. Larger eggs were fertilized at low sperm concentrations, whilst smaller eggs were successfully fertilized at high sperm concentrations. These differences in fertilized egg size resulted in differences in the development rate, hatching success and mean size of the subsequent larvae. Our results suggest that, in contrast to females that reproduce by other mating systems, free-spawning mothers lack some control over the provisioning of offspring. Furthermore, because males can alter the sperm environment, they can exert paternal (non-genetic) control over key offspring characteristics.

Does egg competition occur in marine broadcast-spawners?

When the availability of sperm limits female reproductive success, competition for sperm, may be an important broker of sexual selection. This is because sperm limitation can increase the variance in female reproductive success, resulting in strong selection on females to compete for limited fertilization opportunities. Sperm limitation is probably common in broadcast-spawning marine invertebrates, making these excellent candidates for investigating scramble competition between broods of eggs and its consequences for female reproductive success. Here, we report our findings from a series of experiments that investigate egg competition in the sessile, broadcast-spawning polychaete Galeolaria caespitosa. We initially tested whether the order in which eggs encounter sperm affects their fertilization success at two ecologically relevant current regimes. We used a split-clutch-split-ejaculate technique to compare the fertilization success of eggs from individual females that had either first access (competition-free treatment) or second access (egg competition treatment) to a batch of sperm. We found that fertilization success depended on the order in which eggs accessed sperm; eggs that were assigned to the competition-free treatment exhibited significantly higher fertilization rates than those assigned to the egg competition treatment at both current speeds. In subsequent experiments we found that prior exposure of sperm to eggs significantly reduced both the quantity and quality of sperm available to fertilize a second clutch of eggs, resulting in reductions in fertilization success at high and low sperm concentrations. These findings suggest that female traits that increase the likelihood of sperm-egg interactions (e.g. egg size) will respond to selection imposed by egg competition.

Voice and speech characteristics and vocal hygiene in novice and professional voice broadcast journalists

Knowledge of differences in voice and speech characteristics between novice and professional broadcasters is essential for effective education of broadcast journalism students. Because newsreaders rely on optimal voice production, information pertaining to vocal hygiene is also important. The first aim of this study was to compare the voice and speech characteristics of professional newsreaders, student newsreaders and control participants. The second aim was to compare the awareness and use of vocal hygiene across these groups. Professional radio newsreaders, broadcast journalism students and two matched control groups were included in the study. Each participant recorded a news bulletin and completed a questionnaire on vocal hygiene. Data analysis of the recording included objective analysis and perceptual ratings by a panel of three judges. Significant student-professional differences were found. Compared to both the students and the control groups, the professional newsreaders had greater variation in speaking fundamental frequency, a faster rate of speech, fewer pronunciation errors and higher perceptual ratings on vocal quality, emphasis, continuity, phrasing and style of newsreading. Female professional newsreaders had a higher speaking fundamental frequency than both their control participants and the student newsreaders. Comparison of vocal hygiene awareness revealed few significant differences between any of the groups.

Reliably estimating the effect of toxicants on fertilization success in marine broadcast spawners

Recently, there has been a dramatic increase in the number of ecotoxicological studies examining the effects of toxicants on fertilization success in marine broadcast spawners and it appears that this life-history stage is one of the most vulnerable to toxicants. Most of the studies examining this issue use single sperm concentrations in their assays. Here, I discuss recent advances in fertilization ecology that suggest this technique has some severe limitations resulting in unreliable estimations of the size and direction of toxicant effects. I present an alternative assay technique and two metrics (F-max and [Sperm](max)) that will reliably estimate the size of a toxicant's effect on fertilization success. This technique has the added advantage of making comparisons among species and studies easier without an impractical increase in effort. (c) 2006 Elsevier Ltd. All rights reserved.

In situ measures of spawning synchrony and fertilization success in an intertidal, free-spawning invertebrate

The rocky intertidal zone has the potential to be one of the harshest environments for free-spawning organisms, but empirical data on fertilization success are scarce. Here, I report on an intertidal, solitary ascidian, Pyura stolonifera, which was observed to spawn at low tide. At a scale likely to be most important to gametes (metres, duration of tide), approximately 30% of individuals in the population were spawning synchronously. Spawned gametes remained in a viscous matrix and this appeared to minimise their dilution. Fertilization success varied greatly among individuals (0 to 92%) and was related to the distance to the nearest neighbouring spawner. Occasional wave wash facilitated the movement of sperm between spawners. Fertilization success in some individuals was limited by the scarcity of sperm whilst the experimental addition of sperm did not increase success in others.

Sources of variation in larval quality for free-spawning marine invertebrates: Egg size and the local sperm environment

There has been growing interest in the effects of variation in larval quality on the post-larval performance of adult marine invertebrates. Variation in egg/larval size is an obvious source of variation in larval quality but sources of variation have received little attention. For broadcast spawners, larval size may vary according to the local sperm environment but the generality of this result is unclear. Here, we show that, for a solitary ascidian, a polychaete and an echinoid, larval size is affected by the concentration of sperm present during fertilization. Larvae that are produced at high sperm concentrations are smaller than larvae that are produced from eggs exposed to low sperm concentrations. We also show that for three ascidians and an asteroid, egg size increases with maternal body size. These differences in larval size are likely to affect larval and subsequent adult performance in the field. Given that sperm concentrations in the field can fluctuate widely, it is likely that larval quality in free-spawning marine invertebrates will also vary widely.

Radio leaks: Presenting and contesting leaks in radio news broadcasts

his paper analyzes the discursive construction and contestation of ‘leaked’ stories in news broadcast programmes. Drawing on a sample of BBC Radio 4 news programmes recorded between May and June 2000, we analyze four items of news presented as leaks about upcoming events. We suggest that these examples highlight the leaking of information as a valuable newsworthy commodity in that it not only allows news organizations to report what is going to be news before it happens but also enables speculative discourse as to the meaning of the event yet to happen. However, in order for a story to be accepted as a leak it must be seen to fulfil a number of criteria. With this in mind, we identify four features accompanying the introduction of the news items as leaks in the process of authentification: secrecy, authorship/ownership and future orientation. The article then discusses how these features are used when contesting the status of a news story as a leak, and how temporal play contributes to downgrading the content of the leak and, hence, its relevance, immediacy and newsworthiness.

Effects of the herbicide diuron on the early life history stages of coral

The effects of the herbicide diuron on the early life history stages of broadcast spawning and brooding corals were examined in laboratory experiments. Fertilisation of Acropora millepora and Montipora aequituberculata oocytes were not inhibited at diuron concentrations of up to 1000 mu gl(-1). Metamorphosis of symbiont-free A. millepora larvae was only significantly inhibited at 300 mu gl(-1) diuron. Pocillopora damicornis larvae, which contain symbiotic dinoflagellates, were able to undergo metamorphosis after 24h exposure to diuron at 1000 mu gl(-1). Two-week old P. damicornis recruits on the other hand were as susceptible to diuron as adult colonies, with expulsion of symbiotic dinoflagellates (bleaching) evident at 10 mu gl(-1) diuron after 96 h exposure. Reversible metamorphosis was observed at high diuron concentrations, with fully bleached polyps escaping from their skeletons. Pulse amplitude modulation (PAM) chlorophyll fluorescence techniques demonstrated a reduction in photosynthetic efficiency (Delta F/F'(m)) in illuminated P. dami- cornis recruits after a 2h exposure to 1 mu gl(-1) diuron. The dark-adapted quantum yields (F-v/F-m also declined, indicating chronic photoinhibition and damage to photosystem H. Crown Copyright (c) 2004 Published by Elsevier Ltd. All rights reserved.

Editorial

This article presents information on the September 2005 issue of the "Australian Journal of Communication." The papers by Dunn and Churchman in this issue of the journal were delivered at the very successful Annual Conference of the Australian and New Zealand Communication Association, hosted by Colleen Mills at the University of Canterbury, Christchurch, New Zealand, in July 2005. Dunn's presidential address, on the importance of maintaining public broadcasting, is based on her longterm work at the Australian Broadcasting Commission and her current research at the University of Sydney. Many of the other papers in this issue are related to politics and the media in Australia and New Zealand. Cover discusses how the processes of digitisation and a user-based taste for interactivity have far-reaching broadcast television. In her paper, van Vuuren compares the policy and regulation, practice, and theoretical development of the community broadcasting and community information and communication technology (lCT) sectors in Australia, arguing that the ICT sector can benefit from a knowledge of the way in which the older community broadcasting sector has demonstrated an ability to deliver its services with very limited government support.

Busy saying nothing new: Live silence in TV reporting of 9/11

News of the attacks on New York and Washington on September 11th 2001 spread fast, mainly through dramatic images of the events broadcast via a global television media, particularly 24-hour news channels such as BBC News 24 and CNN. Following the initial report many news channels moved to dedicated live coverage of the story. This move, to what Liebes (1998) describes as a 'disaster marathon', entails shifting from the routine, regular news agenda to one where the event and its aftermath become the main story and reference for all other news. In this paper, we draw upon recordings from the BBC News 24 channel on September 11th 2001 during the immediate aftermath of the attacks on the World Trade Centre and Pentagon to argue that the coverage of this event, and other similar types of events, may be characterised as news permeated with strategic and emergent silences. Identifying silence as both concrete and metaphorical, we suggest that there are a number of types of silence found in the coverage and that these not only act to cover for lack of new news, or give emphasis or gravitas, but also that the vacuum created by a lack of news creates an emotional space in which collective shock, grieving or wonder are managed through news presented as phatic communion.

A simulation analysis of the market effect of the Australian Broadcasting Corporation

In this paper we utilise a stochastic address model of broadcast oligopoly markets to analyse the Australian broadcast television market. In particular, we examine the effect of the presence of a single government market participant in this market. An examination of the dynamics of the simulations demonstrates that the presence of a government market participant can simultaneously generate positive outcomes for viewers as well as for other market suppliers. Further examination of simulation dynamics indicates that privatisation of the government market participant results in reduced viewer choice and diversity. We also demonstrate that additional private market participants would not result in significant benefits to viewers.

Enacting cultural diversity through multicultural radio in Australia

Australia is second only to Israel in being the world’s most culturally diverse nation, based largely on high levels of immigration in the second part of the 20th century. From the 1970s onwards, Australia formally recognized the massive social changes brought about by postwar immigration, and provided legislation to incorporate cultural diversity into everyday lives. One such ‘legislative’ enactment saw the establishment of multicultural broadcasting in Australia, as arguably a world-first, both in its comprehensiveness and diversity. Today, Australia has a public sector corporation, the Special Broadcasting Service, administering five radio services in 68 languages. Also, the Community Radio sector produces multicultural programming in 100 languages through a number of its 330 broadcast and 207 narrowcast stations. This article examines the relationship between radio and its communities. It argues that despite the ‘profile’ of SBS television, radio is much closer to its constituent communities, and therefore plays a greater role in enabling those communities to speak their own histories, beyond the confines of a consensual Anglophile paradigm.

Direct seeding to restore rainforest species: Microsite effects on the early establishment and growth of rainforest tree seedlings on degraded land in the wet tropics of Australia

Reforestation in tropical areas is usually attempted by planting seedlings but, direct seeding (the artificial addition or sowing of seed) may be an alternative way of accelerating forest recovery and successional processes. This study investigated the effects of various sowing treatments (designed to create different microsite conditions for seed germination) and seed sizes on the early establishment and growth of directly sown rainforest tree species in a variety of experimental plots at three sites in the wet tropical region of north-cast Queensland, Australia. The different sowing treatments were found to have significant effects on seedling establishment. Broadcast sowing treatments were ineffective and resulted in very poor seedling establishment and high seed wastage. Higher establishment rates occurred when seeds were buried. Seed size was found to be an important factor affecting establishment in relation to micro-site condition. In general, larger seeded species had higher establishment rates at all three sites than species of small and intermediate seed size, but only in sowing treatments where seeds were buried. Overall these results suggest that direct sowing of seed can be used as a too] to accelerate recolonisation of certain rainforest tree species on degraded tropical lands, but initial success will be dependent on the choice of sowing method and its suitability for the seed types selected. The results also indicate that the recruitment of naturally dispersed tree species at degraded sites is likely to be severely limited by the availability of suitable microsites for seed germination. Consequently the natural recovery of degraded sites via seed rain can be expected to be slow and unpredictable, particularly in areas where soil compaction has occurred. (c) 2006 Elsevier B.V. All rights reserved.