Regeneration mechanisms in Syllidae (Annelida)

• Published in: Regeneration Vol. 5; no. 1; pp. 26 - 42
• Main Authors: Ribeiro, Rannyele P., Bleidorn, Christoph, Aguado, M. Teresa
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-03-2018; John Wiley and Sons Inc
• Subjects: Animals; annelid; Annelida; Bifurcations; epimorphosis; Fission; morphallaxis; Regeneration; Reproduction (biology); Review; schizogamy; Species; Syllidae; morphallaxis; epimorphosis; schizogamy; annelid; fission
• ISSN: 2052-4412; 2052-4412
• DOI: 10.1002/reg2.98

Syllidae is one of the most species‐rich groups within Annelida, with a wide variety of reproductive modes and different regenerative processes. Syllids have striking ability to regenerate their body anteriorly and posteriorly, which in many species is redeployed during sexual (schizogamy) and asexual (fission) reproduction. This review summarizes the available data on regeneration in syllids, covering descriptions of regenerative mechanisms in different species as well as regeneration in relation to reproductive modes. Our survey shows that posterior regeneration is widely distributed in syllids, whereas anterior regeneration is limited in most of the species, excepting those reproducing by fission. The latter reproductive mode is well known for a few species belonging to Autolytinae, Eusyllinae, and Syllinae. Patterns of fission areas have been studied in these animals. Deviations of the regular regeneration pattern or aberrant forms such as bifurcated animals or individuals with multiple heads have been reported for several species. Some of these aberrations show a deviation of the bilateral symmetry and antero‐posterior axis, which, interestingly, can also be observed in the regular branching body pattern of some species of syllids.
Syllids regenerate in their normal life cycle, either as a step of reproduction or post‐injury. In this review, we summarized the available information about the mechanisms of regeneration in syllids. We discuss the relationship between regeneration and reproduction, pathways of anterior and posterior regeneration, and cells and organs involved. We compiled a valuable source of information for future investigations on regeneration, stem cells and establishment of the body plan in syllids.