From aggregates to integrates: physiological aspects of modularity in colonial animals

Physiological adaptations of colonies in the areas of resource-sharing, defensive behaviour and locomotion are reviewed and discussed. Exchange of nutrients between zooids is a fundamental attribute of true colonies, although the transport systems involved vary and, in some cases, complex junctional structures appear to regulate passage of materials between zooids, as in the parallel case of interconnected cell systems. It is not known if regulatory molecules, as well as nutrients, pass via these interzooidal pathways.