Free-living flatworms under the knife: past and present

Abstract

Traditionally, regeneration research has been closely tied to flatworm research, as flatworms (Plathelminthes) were among the first animals where the phenomenon of regeneration was discovered. Since then, the main focus of flatworm regeneration research was on triclads, for which various phenomena were observed and a number of theories developed. However, free-living flatworms encompass a number of other taxa where regeneration was found to be possible. This review aims to display and to compare regeneration in all major free-living flatworm taxa, with special focus on a new player in the field of regeneration, Macrostomum lignano (Macrostomorpha). Findings on the regeneration capacity of this organism provide clues for links between regeneration and (post-)embryonic development, starvation, and asexual reproduction. The role of the nervous system and especially the brain for regeneration is discussed, and similarities as well as particularities in regeneration among free-living flatworms are pointed out.

Reconsidering regeneration in metazoans: an evo-devo approach

“…Neoblasts, however, and regenerative capabilities in general are also present in the more basally branching orders Macrostomorpha and Catenulida (Dirks et al, 2012;Martín-Durán and Egger, 2012). Egger and co-workers note that most flatworm taxa lack the ability to regenerate brain, eyes, pharynx and statocyst (Egger et al, 2007). The other major clade of regenerating flatworms are the acoels, where at least one species shares the regenerative mechanisms of planarians, i.e., the presence of neoblasts, defined by their behavior and by the expression of Piwi, and conserved toolkit of axes formation (De Mulder et al, 2009;Srivastava et al, 2014).…”

Autophagy meets planarians

“…2 Usually, asexual planarians are fully capable of regeneration whereas some sexual species can at best only partially regenerate. 16 However, not all asexual triclad species have the same capacity to regenerate 62,89,90 and it is precisely those species that are more adept that have been historically selected for the study of regeneration, such as Girardia tigrina, Schmidtea mediterranea, Schmidtea polychroa or Dugesia japonica. Asexual planarians can regenerate after amputation as a consequence of injury or under experimental conditions.…”

Demography and feeding behavior of Stenostomum leucops (Dugés, 1828)

“…Most turbellarians have neoblasts (Newmark and Alvarado, 2000) which allow them to be good models for this type of research. Neoblasts also allow these multicellular organisms to reproduce asexually, primarily by transverse fission, which complicates the study of their demographic characteristics, whereby these studies are scarce and the data are highly variable (Egger et al, 2007;Mouton et al, 2009;Dunkel et al, 2011).…”