Stolonial Movement: A New Type of Whole-Organism Behavior in Porifera.

Sponges (phylum Porifera) traditionally are represented as inactive, sessile filter-feeding animals devoid of any behavior except filtering activity. However, different time-lapse techniques demonstrate that sponges are able to show a wide range of coordinated but slow whole-organism behavior. The present study concerns a peculiar type of such behavior in the psychrophilic demosponge Amphilectus lobatus: stolonial movement. During stolonial movement, sponges produce outgrowths (stolons) that crawl along a substrate with a speed of 4.4 ± 2.2 μm min-1 and branch, thus forming a complex net covering a considerable area of a substrate. This net is used by sponges to search for new points with appropriate environmental conditions for individual relocation. After such points are found, all cells of the parental sponge migrate through stolons, leaving a naked parental skeleton, forming one or several filial sponges in the new location. Thus, stolonial movement combines traits of crawling along the substrate and asexual reproduction. This behavior relies on massive cell dedifferentiation followed by coordinated cell migration to the point of new sponge body formation and their subsequent differentiation into specialized cell types.