Image scoring and cooperation in a cleaner fish mutualism

Humans are highly social animals and often help unrelated individuals that may never reciprocate the altruist's favour(1-5). This apparent evolutionary puzzle may be explained by the altruist's gain in social image: image-scoring bystanders, also known as eavesdroppers, notice the altruistic act and therefore are more likely to help the altruist in the future(5-7). Such complex indirect reciprocity based on altruistic acts may evolve only after simple indirect reciprocity has been established, which requires two steps. First, image scoring evolves when bystanders gain personal benefits from information gathered, for example, by finding cooperative partners(8-10). Second, altruistic behaviour in the presence of such bystanders may evolve if altruists benefit from access to the bystanders. Here, we provide experimental evidence for both of the requirements in a cleaning mutualism involving the cleaner fish Labroides dimidiatus. These cleaners may cooperate and remove ectoparasites from clients or they may cheat by feeding on client mucus(11,12). As mucus may be preferred over typical client ectoparasites(13), clients must make cleaners feed against their preference to obtain a cooperative service. We found that eavesdropping clients spent more time next to 'cooperative' than 'unknown cooperative level' cleaners, which shows that clients engage in image-scoring behaviour. Furthermore, trained cleaners learned to feed more cooperatively when in an `image-scoring' than in a 'non-image-scoring' situation.

Insights on food and nutrition in the Federated States of Micronesia: a review of the literature

Background: Nutrition-related disorders, including vitamin A deficiency (VAD) and chronic diseases, are serious problems in the Federated States of Micronesia (FSM). Many suggest that these disorders are new problems related to dietary and lifestyle changes. In the past four decades, imported foods, such as white rice, flour, sugar, refined foods and fatty meats, have increasingly replaced local foods in the diet. Aim: A literature review was conducted to understand underlying issues related to dietary change and obtain insights for nutrition research and interventions. Method: Published and unpublished papers from different disciplines were reviewed and collated for information on food and nutrition in FSM. Topics covered were historical background, local foods, infant and child feeding, dietary assessment, and nutritional status. Particular focus was on information and data relating to VAD, the primary topic that led to the review of the literature. Conclusions: FSM, a tropical country of abundant agricultural resources, has suffered a great loss in production and consumption of local foods. Inconsistent external and internal government policies and food aid programmes have contributed to the problem. Further research on the nutrient content of local foods and factors affecting production, acquisition and consumption is needed, as well as a broad, well-planned, intersectoral intervention aimed at dietary improvement for all age groups in the population.