Fig. 13.

Working model of ctenophore regeneration. Timeline of the morphological and cellular events underlying ctenophore regeneration. Apical organ regeneration is used as an example. Proliferating cells (EdU+) are colored in magenta. Wound closure is initiated immediately after surgery with the edges of the wound forming a round circumference that reduces in diameter until meeting and is completed within 1–2 h after amputation. Reorganization of tissue including aggregation of round-shaped cells at the wound epithelium—potentially derived from dedifferentiation events—takes place during the first 6 h after injury (cell proliferation-independent phase). Cell proliferation is activated at the wound site between 6 and 12 h after amputation, and it reaches a maximum at 24 h, when the primordia of the missing structures are formed. After this peak of cell proliferation, the number of proliferating cells at the wound site decreases while cells start to specify and differentiate into the final structures