Abstract
Sponges are known to possess remarkable reconstitutive and regenerative abilities ranging from common wounding or body part regeneration to more impressive re-building of a functional body from dissociated cells. Among the four sponge classes, Homoscleromorpha is notably the only sponge group to possess morphologically distinct basement membrane and specialized cell-junctions, and is therefore considered to possess true epithelia. The consequence of this peculiar organization is the predominance of epithelial morphogenesis during ontogenesis of these sponges. In this work we reveal the underlying cellular mechanisms used during morphogenesis accompanying ectosome regeneration in the homoscleromorph sponge model: Oscarella lobularis. We identified three main sources of novel exopinacoderm during the processes of its regeneration and the restoration of functional peripheral parts of the aquiferous system in O. lobularis: (1) intact exopinacoderm surrounding the wound surface, (2) the endopinacoderm from peripheral exhalant and inhalant canals, and (3) the intact choanoderm found on the wound surface. The basic morphogenetic processes during regeneration are the spreading and fusion of epithelial sheets that merge into one continuous epithelium. Transdifferentiation of choanocytes into exopinacocytes is also present. Epithelial-mesenchymal transition is absent during regeneration. Moreover, we cannot reveal any other morphologically distinct pluripotent cells. In Oscarella, neither blastema formation nor local dedifferentiation and proliferation have been detected, which is probably due to the high morphogenetic plasticity of the tissue. Regeneration in O. lobularis goes through cell transdifferentiation and through the processes, when lost body parts are replaced by the remodeling of the remaining tissue. Morphogenesis during ectosome regeneration in O. lobularis is correlated with its true epithelial organization. Knowledge of the morphological basis of morphogenesis during Oscarella regeneration could have important implications for our understanding of the diversity and evolution of regeneration mechanisms in metazoans, and is a strong basis for future investigations with molecular-biological approaches.
Highlights
The ability to regenerate is widespread throughout the animal kingdom
Epimorphosis requires active cellular proliferation prior to the replacement of the lost body part. In some animals, such as cnidarians, planarians and annelids, pre-existing stem cells begin to proliferate and migrate to the damaged area in response to injury [9]. These cells form a mass of proliferating cells, known as the regeneration blastema, which will later differentiate into the specialized cells that comprise the regenerated structure [2]
Morphallaxis refers to the type of regeneration in which lost body parts are replaced by the remodeling of the remaining tissue
Summary
The ability to regenerate is widespread throughout the animal kingdom. It has been observed in most animal phyla but with a great variability of regenerative potentialities: from renewing single cell types such as in the case of the salamander lens [1] to complete body parts, such as in the case of planarian regeneration [2], with all possible intermediates (tissues, organs) [3,4]. Epimorphosis requires active cellular proliferation prior to the replacement of the lost body part In some animals, such as cnidarians, planarians and annelids, pre-existing stem cells begin to proliferate and migrate to the damaged area in response to injury [9]. Morphallaxis refers to the type of regeneration in which lost body parts are replaced by the remodeling of the remaining tissue. In this process, little or no cellular proliferation takes place during the regeneration (a well-described example of this process is Hydra [10]). The notable feature of morphallaxis is that the majority of regenerated tissue comes from tissue which is already present in the organism
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
