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Unformatted text preview: Vol 441 | 25 May 2006 421 Avoidance of disease by social lobsters These gregarious animals shun lobsters that carry a lethal virus, even when they still seem to be healthy. Transmissible pathogens are the bane of social animals 1 , so they have evolved behaviours to decrease the probability of infection 2,3 . There is no record, however, of social animals avoid- ing diseased individuals of their own species in the wild. Here we show how healthy, nor- mally gregarious Caribbean spiny lobsters ( Panulirus argus ) avoid conspecifics that are infected with a lethal virus. Early detection and avoidance of infected, though not yet infectious, individuals by healthy lobsters con- fers a selective advantage and highlights the importance of host behaviour in disease trans- mission among natural populations. Panulirus argus virus 1 (PaV1) is a lethal pathogenic virus that infects juvenile spiny lob- sters 4 . It is transmitted by physical contact and, among the smallest juveniles, through sea water. Spiny lobsters are social and share com- munal dens, so these modes of viral transmis- sion could have devastating consequences in the absence of a mechanism to check its spread. During underwater surveys of juvenile lob- sters, we observed that infected lobsters rarely shared shelters with conspecifics (less than 7% shared dens and more than 93% were solitary), even though healthy lobsters generally pre- ferred to live together (more than 56% shared dens and less than 44% were solitary). To test whether this could be explained by healthy lobsters avoiding diseased individuals, we set up a laboratory experiment (for meth- ods, see supplementary information) in which healthy and diseased lobsters were given a choice between an empty den and one contain- ing either a healthy or a diseased individual....
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