There are new articles in four PLoS journals today. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week - you go and look for your own favourites:
Colour-marking polymorphism is widely distributed among cryptic species. To account for the adaptive significance of such polymorphisms, several hypotheses have been proposed to date. Although these hypotheses argue over the degree of camouflage effects of marking morphs (and the interactions between morphs and their microhabitat backgrounds), as far as we know, most empirical evidence has been provided under unnatural conditions (i.e., using artificial prey). Tetrix japonica, a pygmy grasshopper, is highly polymorphic in colour-markings and occurs in both sand and grass microhabitats. Even within a microhabitat, T. japonica is highly polymorphic. Using humans as dummy predators and printed photographs in which various morphs of grasshoppers were placed against different backgrounds, we addressed three questions to test the neutral, background heterogeneity, and differential crypsis hypotheses in four marking-type morphs: 1) do the morphs differ in the degree of crypsis in each microhabitat, 2) are different morphs most cryptic in specific backgrounds of the microhabitats, and 3) does the morph frequency reflect the degree of crypsis? The degree of camouflage differed among the four morphs; therefore, the neutral hypothesis was rejected. Furthermore, the order of camouflage advantage among morphs differed depending on the two types of backgrounds (sand and grass), although the grass background consistently provided greater camouflage effects. Thus, based on our results, we could not reject the background heterogeneity hypothesis. Under field conditions, the more cryptic morphs comprised a minority of the population. Overall, our results demonstrate that the different morphs were not equivalent in the degree of crypsis, but the degree of camouflage of the morphs was not consistent with the morph frequency. These findings suggest that trade-offs exist between the camouflage benefit of body colouration and other fitness components, providing a better understanding of the adaptive significance of colour-markings and presumably supporting the differential crypsis hypothesis.
Adolescents, Adults and Rewards: Comparing Motivational Neurocircuitry Recruitment Using fMRI:
Adolescent risk-taking, including behaviors resulting in injury or death, has been attributed in part to maturational differences in mesolimbic incentive-motivational neurocircuitry, including ostensible oversensitivity of the nucleus accumbens (NAcc) to rewards. To test whether adolescents showed increased NAcc activation by cues for rewards, or by delivery of rewards, we scanned 24 adolescents (age 12-17) and 24 adults age (22-42) with functional magnetic resonance imaging while they performed a monetary incentive delay (MID) task. The MID task was configured to temporally disentangle potential reward or potential loss anticipation-related brain signal from reward or loss notification-related signal. Subjects saw cues signaling opportunities to win or avoid losing $0, $.50, or $5 for responding quickly to a subsequent target. Subjects then viewed feedback of their trial success after a variable interval from cue presentation of between 6 to17 s. Adolescents showed reduced NAcc recruitment by reward-predictive cues compared to adult controls in a linear contrast with non-incentive cues, and in a volume-of-interest analysis of signal change in the NAcc. In contrast, adolescents showed little difference in striatal and frontocortical responsiveness to reward deliveries compared to adults. In light of divergent developmental difference findings between neuroimaging incentive paradigms (as well as at different stages within the same task), these data suggest that maturational differences in incentive-motivational neurocircuitry: 1) may be sensitive to nuances of incentive tasks or stimuli, such as behavioral or learning contingencies, and 2) may be specific to the component of the instrumental behavior (such as anticipation versus notification).
Invaders on the Wing (book review):
The deliberate or accidental introduction of species beyond their natural range has been one of the major consequences of the growth of trade, travel, and tourism in recent times. Many introduced species fail to establish or to spread significantly, but many others become successful invaders. Invasive alien species can transform natural ecosystems and cause extinctions of native species. As a result, invasive species are now recognized in the IUCN Red List as one of the main threats to native biodiversity worldwide. In some parts of the world, especially on oceanic islands and previously isolated landmasses, they are arguably now a more important threat than factors such as habitat loss or overexploitation, which tend to preoccupy conservationists in continental landscapes that humans have modified over thousands of years. For example, in New Zealand there is now a major "biosecurity" focus on preventing new invasions, eradicating introduced mammals from offshore islands, and managing a suite of invasive species on the mainland.
Buruli ulcer, caused by Mycobacterium ulcerans, is a devastating skin disease. Most cases of Buruli ulcer occur in poor rural communities. As a result, treatment is frequently sought too late and about 25% of those infected--particularly children--become permanently disabled. Outbreaks of Buruli ulcer have always been associated with swampy areas. However, the route(s) of bacillus transmission is (are) still unclear. This Mycobacterium species resides in water where it colonizes many ecological niches such as aquatic plants, herbivorous animals and predatory/carnivorous insects. For several years the role of water bugs as hosts and vectors of M. ulcerans was suspected and was demonstrated under laboratory conditions. The aim of this work was to further assess the role of water bugs as hosts and vectors of M. ulcerans in environmental context. This work identifies several water bug families as hosts of M. ulcerans in Buruli ulcer endemic area. The detection of bacilli in saliva of human biting insects provides further evidence for their role in M. ulcerans transmission. Interestingly, three of these insects are good flyers, and as such could participate in M. ulcerans dissemination.
This PLoS Medicine series began by outlining how much we fail mothers, newborns, and children in Africa by not implementing effectively what we know saves lives and improves health [1],[2]. It is clear that countries in Africa are falling behind not only on improving maternal, newborn, and child health but on the Millennium Development Goals 4, 5, and 6 more generally. Why is there such a wide gap between what we know and what we do? While technical knowledge about what could be done is available, actual implementation is neither straightforward nor easy in the often difficult circumstances on the ground. The many competing priorities--along with limited logistic capacity, a lack of political will, and inadequate infrastructure--also constrain the extent to which effective health packages are delivered to those who need them most.
The crisis of avoidable maternal, newborn, and child deaths in developing countries is currently a major focus for the global health community (Box 1), and it will be one of the leading issues discussed at the September 2010 Summit on the Millennium Development Goals (MDGs) [1]-[3]. Many countries are off track to reach the 2015 child and maternal health MDGs (MDGs 4 and 5), and additional donor assistance will be needed to help countries get back on track.
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