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Mills S.C.,CNRS Insular Research Center and Environment Observatory
Coral Reefs | Year: 2012

The density-dependent prophylaxis hypothesis predicts that individuals at high density will invest more resources into immune defence than individuals at lower densities as a counter-measure to density-dependent pathogen transmission rates. Evidence has been found for this hypothesis in insects, but not in a non-arthropod taxon. To investigate this hypothesis in the coral-eating crown-of-thorns sea star, Acanthaster planci, density treatments were set up over 21 days, and pathogen infection was simulated with bacterial injection. Five immune responses: amoebocyte count, amoebocyte viability, lysosomal membrane integrity, respiratory burst and peroxidase activity were all upregulated at high density. These results demonstrate that immune investment shows phenotypic plasticity with adult population density in agreement with the density-dependent prophylaxis hypothesis. Here I show that the density-dependent prophylaxis hypothesis is neither dependent on larval density nor restricted to insects, and hence may potentially have important consequences on disease dynamics in any species with widely fluctuating population densities. This is the first demonstration of the density-dependent prophylaxis hypothesis outside arthropods. © 2012 Springer-Verlag. Source

Sweet M.J.,Northumbria University | Bythell J.C.,Northumbria University | Nugues M.M.,CNRS Insular Research Center and Environment Observatory
PLoS ONE | Year: 2013

Benthic algae are associated with coral death in the form of stress and disease. It's been proposed that they release exudates, which facilitate invasion of potentially pathogenic microbes at the coral-algal interface, resulting in coral disease. However, the original source of these pathogens remains unknown. This study examined the ability of benthic algae to act as reservoirs of coral pathogens by characterizing surface associated microbes associated with major Caribbean and Indo-Pacific algal species/types and by comparing them to potential pathogens of two dominant coral diseases: White Syndrome (WS) in the Indo-Pacific and Yellow Band Disease (YBD) in the Caribbean. Coral and algal sampling was conducted simultaneously at the same sites to avoid spatial effects. Potential pathogens were defined as those absent or rare in healthy corals, increasing in abundance in healthy tissues adjacent to a disease lesion, and dominant in disease lesions. Potentially pathogenic bacteria were detected in both WS and YBD and were also present within the majority of algal species/types (54 and 100% for WS and YBD respectively). Pathogenic ciliates were associated only with WS and not YBD lesions and these were also present in 36% of the Indo-Pacific algal species. Although potential pathogens were associated with many algal species, their presence was inconsistent among replicate algal samples and detection rates were relatively low, suggestive of low density and occurrence. At the community level, coral-associated microbes irrespective of the health of their host differed from algal-associated microbes, supporting that algae and corals have distinctive microbial communities associated with their tissue. We conclude that benthic algae are common reservoirs for a variety of different potential coral pathogens. However, algal-associated microbes alone are unlikely to cause coral death. Initial damage or stress to the coral via other competitive mechanisms is most likely a prerequisite to potential transmission of these pathogens. © 2013 Sweet et al. Source

Canavesio R.,CNRS Insular Research Center and Environment Observatory
Land Use Policy | Year: 2014

The main political concern in the southern areas of Madagascar is poverty alleviation. To alleviate poverty in the area, the government has chosen to enforce adjustment policies of the World Bank Group. According to the World Bank Group's argument, while artisanal mining is supposed to create significant economic, social and environmental problems, large-scale mining investment results in economic and social prosperity. This paper focuses principally on a re-analysis of the debates regarding the relationship between artisanal and large-scale mining and poverty alleviation in developing countries. Further, the paper offers an alternative viewpoint on these issues based on the example of Madagascar. In the last decade, Madagascar has experienced a significant increase in mining activity. Towards the end of the 90s, informal and artisanal mining emerged as one of the most important economic activities of the area with the development of the Ilakaka frontier. At the same time, foreign investments began to benefit from adjustment policies implemented by the government, and large-scale mining operations also commenced. As the local socio-economic system was deeply affected by these developments, it is wise to monitor the effects of each type of mining operation on poverty alleviation. On the one hand, it appears that governance insufficiency has hampered possibilities for broader economic prosperity through large-scale mining investments. On the other hand, while artisanal mining is frequently condemned by scholars, the negative comments seem to be overly pessimistic, as this activity can be demonstrated to provide considerable economic opportunities for both the native and migrant populations. © 2013 Elsevier Ltd. Source

Mills S.C.,CNRS Insular Research Center and Environment Observatory | Cote I.M.,Simon Fraser University
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

Cheating is common in cooperative interactions, but its occurrence can be controlled by various means ranging from rewarding cooperators to active punishment of cheaters. Punishment occurs in the mutualism involving the cleanerfish Labroides dimidiatus and its reef fish clients. When L. dimidiatus cheats, by taking scales and mucus rather than ectoparasites, wronged clients either chase or withhold further visits to the dishonest cleaner, which leads to more cooperative future interactions. Punishment of cheating L. dimidiatus may be effective largely because these cleaners are strictly site-attached, increasing the potential for repeated interactions between individual cleaners and clients. Here, we contrast the patterns of cheating and punishment in L. dimidiatus with its close relative, the less site-attached Labroides bicolor. Overall, L. bicolor had larger home ranges, cheated more often and, contrary to our prediction, were punished by cheated clients as frequently as, and not less often than, L. dimidiatus. However, adult L. bicolor, which had the largest home ranges, did not cheat more than younger conspecifics, suggesting that roaming, and hence the frequency of repeated interactions, has little influence on cheating and retaliation in cleaner-client relationships. We suggest that roaming cleaners offer the only option available to many site-attached reef fish seeking a cleaning service. This asymmetry in scope for partner choice encourages dishonesty by the partner with more options (i.e. L. bicolor), but to be cleaned by a cleaner that sometimes cheats may be a better option than not to be cleaned at all. © 2010 The Royal Society. Source

Almany G.R.,CNRS Insular Research Center and Environment Observatory
Current Biology | Year: 2015

Summary New work reveals that the large network of no-take marine reserves on the Great Barrier Reef is working splendidly. However, bold, global action is needed to eliminate threats that reserves cannot guard against. © 2015 Elsevier Ltd All rights reserved. Source

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