Fig. 2

Schematic drawings of anterior and posterior regenerative stages in Timarete cf. punctata. The anus is colored in orange, branchiae in blue, chaetae in grey, mouth opening in yellow, nuchal organ in green, and tentacles in red. The dotted line in the upper drawing indicates the side of dissection. Please note that anterior and posterior stages show differences in characteristics and period. Posterior regeneration (left column) started with an invagination stage (pi, 0–2 days after disection), followed by a blastema stage (pb1-2, 3–5 dad) with formation and development of a blastema. Afterwards, during the blastema patterning stage (pp, 4–6 dad) the anus became visible. During the growth stage (pg, from 6 dad onwards) new segments were added by a posterior segment addition zone (SAZ) directly anterior to the pygidium (py). The first stages of anterior regeneration with invagination (ai, 0–1 dad) and blastema formation (ab1-3, 2–4 dad) are comparable to the posterior regeneration, according to the outer morphology. In the early blastema patterning stage (ap1, 4–5 dad) the mouth opening redeveloped. Afterwards, the first pair of tentacles occurred (6–8 dad) and the boundaries of pro- (pr) and peristomium (pe) as well as the nuchal organs became visible by the late blastema patterning stage (ap2, 6–10 dad). With the formation of three segments at once, the re-segmentation stage (ar, 6–11 dad) was reached and continued with sequential addition of three more segments. Also branchiae and a second pair of tentacles were seen first at this stage. Finally, during the growth stage (ag, from day 11 onwards), all described structure increased in size until they reached an adult condition