Sokolova A.M.1*, Ereskovsky A.V.1,2 2025. How gemmules become sponges: known facts and open questions // Invert. Zool. Vol.22. No.3: 383–400 [in English]
1 N.K. Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Vavilova Street 26, Moscow 119334 Russia.
2 Aix Marseille University, Avignon Université, CNRS, IRD, IMBE UMR 7263, Marseille, France.
* Corresponding author
A.M. Sokolova agnisokolova@gmail.com ORCID: https://orcid.org/0000-0002-2056-1310
A.V. Ereskovsky alexander.ereskovsky@imbe.fr ORCID: https://orcid.org/0000-0003-1079-7204
doi: 10.15298/invertzool.22.3.01
ABSTRACT. Freshwater sponges (Demospongiae: Spongillida) have achieved their global distribution largely through gemmules — specialized asexual reproductive structures. Covered with a robust and thick coat, gemmules protect several hundred binucleated pluripotent cells, called thesocytes, from harsh environmental conditions. Gemmules can withstand low temperatures, desiccation, hypoxia, and high salinity, ensuring the survival and dispersal of freshwater sponges. Despite over a hundred years of research, many aspects of gemmule hatching and subsequent sponge development remain unclear. Most studies addressing morphogenetic events during gemmule hatching were conducted in the last century and often do not include microscopic images to support their descriptions. Recently, however, developing gemmules have gained recognition as a model system for cell and developmental biology, representing the entire Porifera phylum. This review compiles existing knowledge about the developmental processes involved in gemmule hatching. We discuss gemmule structure and dormancy, environmental cues triggering germination, morphogenetic processes of hatching and early development, genetic networks underlying sponge body formation, and critical gaps in current knowledge.
KEY WORDS: freshwater sponges, Spongillida, gemmules, dormancy, hatching, early development.