Regeneration is the natural ability to restore or replace damaged or lost body parts following severe injury. This capability is widespread in the animal kingdom, ranging from the regeneration of specific body structures like lizard tails to the remarkable whole-body regeneration seen in some organisms such as earthworms, which can regenerate from just a few segments. Regenerative abilities vary strongly across and within most bilaterian phyla. In contrast, early diverging sister lineages to Bilateria, such as Cnidaria (coral, sea anemone, jellyfish) and Porifera (sponges), generally possess high regenerative abilities. This suggests that regeneration capacity was present at the origin of animal multicellularity or emerged early in animal evolution.
The phylogenetic distribution and intra-phylum variations of regeneration imply a rich and intricate evolutionary history of this trait. Questions regarding whether regeneration is ancestral and intrinsic to animals, as well as why there is such variation in regenerative abilities, remain intriguing issues in biology. While there is a growing body of knowledge on the mechanisms of regeneration across deeply diverged species, a comprehensive understanding of the ancestral state is crucial for fully grasping evolutionary patterns.
Cnidarians and sponges have captured the interest of scientists exploring the field of regeneration for over a century. Models from both groups have played pivotal roles in addressing fundamental evolutionary questions and developing an understanding of the evolutionary origin of key animal traits, including regeneration.
In this seminar, I will present the remarkable regenerative abilities exhibited by the calcareous sponge Sycon and the soft coral Xenia. These fascinating organisms can recover from mere tissue fragments, with Sycon even demonstrating the capability to regenerate from dissociated cells. Delving into the molecular and cellular mechanisms, I will emphasise the quick injury response governed by immediate early genes. This response appears to be a conserved pathway that likely evolved in the common ancestor of all animals. Finally, I will share new insights into the relatively unexplored process of soft coral biomineralisation. Through the integration of bioinformatic and wet lab approaches, I will reveal the transcriptomic signature of scleroblasts, Xenia’s calcifying cells, shedding light on the evolution of cell type programs that orchestrate coral biomineralisation.