Cell proliferation and cell death during whole‐body regeneration in the demosponge Halisarca dujardinii

Sponges (phylum Porifera) are early-branching metazoans demonstrating an outstanding example of whole-body regeneration, cell reaggregation. During the process, single cells form aggregates capable of progressive development and reconstruction of intact sponges. This study provides the first comprehensive analysis of cell proliferation and cell death during cell reaggregation in a marine demosponge, Halisarca dujardinii. Relatively high proliferative activity occurs at the early and late stages of the reaggregation. This proliferation seems to be a consequence of intact tissue turnover rather than a prerequisite for aggregate development. The contribution of cell death is limited to a short period during the aggregate epithelization. Cell reaggregation in demosponges appears to be a morphallactic restorative process relying primarily on cell migration, dedifferentiation, and transdifferentiation.