Regeneration and Musculature in Halved Cassiopea xamachana Ephyrae

Abstract

Adult Cassiopea medusae and their polyps have been known to regenerate tissue in uncontrolled and controlled conditions; however, the regeneration capabilities of Cassiopea xamachana ephyrae are largely unexplored. Here, we detail the development and regeneration of ephyrae under known laboratory conditions. Ephyrae were cut in two and then followed as they regenerated back to complete individuals. We visually document all the developmental stages of the medusa leading up to the trauma and the complete regeneration process of the two halves. We show how ephyrae of C. xamachana, when cut in halves, undergo both regeneration and re-symmetrization, generating, in about 2 weeks, two functional smaller ephyrae with fewer rhopalia and normal behavior. We also show that regeneration is slower in older ephyra.

Fig. 1.

Stereo microscope pictures of C. xamachana ephyrae showing growth of intact and bisected ephyrae. (A) Trajectory of growth in the original ephyra with photographs at days 0, 7, 14, 21, and 28. (B) Visual progress of two fragments with circle back comparison to original medusa, all are on the same scale (see scale bar). Locations of rhopalia are pinpointed with black dots, edges of the bell and oral arms are outlined in black. See description of one ephyra regeneration and development in Supplementary Material.

Fig. 2.

Plots illustrating how ephyrae belonging to different age groups performed regeneration after bisection. (A) Violin plots of the mean (larger circle) ± 1 SD (central line) of the number of days to full wound closure across experimental ages. (B) A linear regression displaying the cut date on the x-axis and the number of days the wound took to close on the y-axis. (C) Plot of wound angles over time in hours post bisection by treatment groups.

Fig. 3.

Violin plot illustrating the bell to oral arm ratio of all individuals by cut date at 14 days post injury. Red circle represents mean, line represents ± 1 SD. Higher ratio means more oral arm or manubrium, lower means more bell.

Fig. 4.

Proportional bar plot containing the proportions of healthy, unhealthy, and dead ephyrae in each treatment and control, 15 days post cut.

Fig. 5.

Drawing of the bell musculature of C. xamachana and pictures of details of stained ephyrae. Both drawing and pictures follow the same orientation, with the top of each figure facing towards the mouth of the ephyra, and the bottom facing the periphery of the bell. (A) Schematic drawing of a C. xamachana ephyra's musculature observed from the oral side. (B) Phalloidin-stained fraction of the oral side of the ephyra, from the base of the oral arms to the rim of the bell. (C) Phalloidin-stained detail of the transition (top to bottom) from the innermost circular coronal band to the undulated coronal band. (D) Phalloidin-stained close up of the intersection (top to bottom) of the outermost coronal muscles with the radial musculature. rm = radial muscles; cm = coronal muscles. PX and DT indicate proximal and distal ends from oral arms. Arrows indicate undulated muscles band, asterisk indicate circular coronal muscles. Scale bar B = 100 µm. Scale bar C, D = 50 µm.

Fig. 6.

Confocal microscope images of actin-stained regenerating ephyrae at timepoints 0 and 24 h after bisection. (A) T (time) = 0 h post amputation (hpa); (B) T = 24 hpa after cut; (C) Close up of the wound site at T = 24 hpa. Scale bar A, B = 1 mm. Scale bar C = 50 µm. See Fig. S6 for T = 48 hpa and T = 72 hpa.