Fig. 2

Light microscopy pictures of the regenerating Sphaerosyllis hystrix. a, b, c, g, h, i anterior regeneration. d, e, f, j, k, l posterior regeneration. Amputation was performed in the midbody region and the regenerating animals were observed for 14 days post amputation (dpa). Immediately after body bisection, the wound is closed by invagination through muscle contraction. Anterior regeneration starts by wound healing (1–3 dpa) and the formation of a small blastema (a). The anterior blastema is formed after 4–6 dpa and no differentiated organ is regenerated until 12 dpa (b, c, g). An incomplete prostomium (head) appeared after 13 dpa, bearing eyes (h), and a pair of minute antennae in 14 dpa (i). Posterior regeneration proceeds more quickly: healing occurred in 2 dpa, the blastema developed from 2 to 4 dpa, and a pygidium with a pair of cirri was first seen after 9 dpa (d, e, f). From 10 to 14 dpa, amputees had regrown new pygidia and a maximum of four posterior segments (j–l). All pictures are in dorsal view. Scale bar 0.2 mm. White dashed lines show amputation level. Black dashed lines show the regenerated eyes. Abs: an, antenna; ey, eye