Figure 1. Regenerative potential of Clytia hemisphaerica jellyfish.

(A–D) Anatomy of Clytia jellyfish. (A) Swimming female jellyfish (m: manubrium; g: gonads; tb: tentacle bulbs). (B) Tetraradial body organization: each umbrella quadrant comprises a radial canal (rc), a gonad (g), and up to 16 tentacle bulbs (tb). The tetraradially-shaped manubrium (m) lies at the center. A peripheral circular canal (cc) connects the tentacle bulbs. Radial smooth muscle fibers (smooth m.) and circular striated muscles (striated m.) line the subumbrellar surface. (C) The umbrella comprises an epithelial exumbrella layer, a connective mesoglea, and a subumbrella layer, constituted by an inner layer associated with the mesoglea and two layers of muscle fibers (smooth and striated). (D) Diagram of the manubrium, lateral view, showing the oral (distal)-aboral (proximal) axis. The base comprises four gastric pouches, connected to the four radial canals. The oral area is organized into four folds (lips). (E–J) Regenerative potential of Clytia. In each cartoon the cut is indicated by an orange dotted line, removed parts are veiled. (E) Manubrium regeneration is completed in 4 days, the white dashed line at 24 hpd circles the cell accumulation. (F) Gonad regeneration over 8 days. (G) Tentacle bulb regeneration over 8 days. (H) Detail of the tip of a regrowing radial canal shown by fluorescence microscopy; neural fibers associated with the canal are stained with an anti-tyr-Tub antibody (red). (I) A quarter jellyfish fragment that morphed within 24 hr into a small jellyfish. A tiny new manubrium was visible after 4 days (arrowhead). (J) Fragment from which the entire bell margin had been removed: it sealed upon itself without further regeneration. Abbreviations: (dpd) days post-dissection, (hpd) hours post-dissection. Scale bars- A,I-J: 1 mm; E-G: 100 µm; H: 20 µm.

Figure 1—figure supplement 1. Organ regeneration in relation to feeding status.

(A,B) Examples of organ ablation in fed individuals, each illustrated by a cartoon showing the cut (as an orange dotted line) and images of the regenerate at successive times. The regenerated gonad (A) and tentacle bulb (B) were both visible after 6 days. (C–E) Quantification of regeneration of gonads, tentacle bulbs and manubria, respectively, in fed versus unfed animals, as indicated. Both groups were fed 12 hr before the dissection, and fed animals were given Artemia every day until the end of the experiment. For gonads (C) and bulbs (D), regeneration rates were variable, but proceeded more reliably in fed jellyfish. (E) Manubrium regeneration was highly stereotypical. (F, G) Comparison of the dimension of endogenous versus regenerated manubria (4 dpd). The length from base to lip (F) was longer for endogenous manubria (n = 20 jellyfish), while their bases (G) were of comparable sizes. Statistics: two tailed t-test. Raw data for (C–G): Figure 1—figure supplement 1—source data 1. The images in A and B are also shown in Figure 1F and G, respectively. Scale bars: 100 µm.

Figure 1—figure supplement 2. Umbrella restorative potential.

Examples of different kinds of ablation. Left cartoon illustrates the cut (as an orange dotted line, removed parts are veiled), in the middle is an image of the regenerate at 24 hpd, and to the right there is a cartoon illustrating the regenerate. All types of damage (A–T) triggered remodeling of the umbrella, driven by rapid reduction of the cut edges. Segments of severed peripheral circular canal fused together, defining the final perimeter of the regenerate. Circular shape was largely restored in all cases, but the original tetraradial symmetry was not recovered (exceptions in A, B). The images in C, D and T are also shown in Figures 8A, 1I and J, respectively.