Intraspecific variability of cell reaggregation during reproduction cycle in sponges

The ability of sponge cells to reaggregate and reconstruct intact functional organism is known for more than 100 years. This process was studied in numerous species of sponges, and its interspecific variability is well described. However, some data also indicate the existence of a certain intraspecific variability of the cell reaggregation. The present study deals with the cell reaggregation in two demosponges, Halichondria panicea and Halisarca dujardinii, during different periods of their sexual reproduction. In both species, cell reaggregation shows a common pattern at all studied periods of reproduction. However, the course of the reaggregation process significantly depends on the reproduction period of an individual used in the experiment, thus demonstrating pronounced intraspecific variability, which concerns the rate of the cell reaggregation and the final stage of the process. This variability occurs due to tissue rearrangements that accompany reproduction and changes cell composition and amount of available somatic stem cells in sponge tissues, and consequently alters morphogenetic potencies of a cell suspension and multicellular aggregates. In both Halichondria panicea and Halisarca dujardinii, the growth period is the most favorable for the reaggregation process, while the cell reaggregation is depressed during periods of embryogenesis and restoration of somatic tissues after the reproduction. At the same time, the structure of a particular stage of reaggregation and morphogenetic processes underlying the development of multicellular aggregates are always identical, independently from the period of the reproductive cycle.