, Volume 15, Issue 3, pp 279–292 | Cite as

Autophagy and apoptosis in planarians

  • Cristina González-Estévez
  • Emili Saló
Unusual Model Systems for Cell Death Research


Adult planarians are capable of undergoing regeneration and body remodelling in order to adapt to physical damage or extreme environmental conditions. Moreover, most planarians can tolerate long periods of starvation and during this time, they shrink from an adult size to, and sometimes beyond, the initial size at hatching. Indeed, these properties have made them a classic model to study stem cells and regeneration. Under such stressful conditions, food reserves from the gastrodermis and parenchyma are first used up and later the testes, copulatory organs and ovaries are digested. More surprisingly, when food is again made available to shrunken individuals, they grow back to adult size and all their reproductive structures reappear. These cycles of growth and shrinkage may occur over long periods without any apparent impairment to the individual, or to its future maturation and breeding capacities. This plasticity resides in a mesoderm tissue known as the parenchyma, which is formed by several differentiated non-proliferating cell types and only one mitotically active cell type, the neoblasts, which represent approximately 20–30% of the cells in the parenchyma. Neoblasts are generally thought to be somatic stem-cells that participate in the normal continuous turnover of all cell types in planarians. Hence, planarians are organisms that continuously adapt their bodies (morphallaxis) to different environmental stresses (i.e.: injury or starvation). This adaptation involves a variety of processes including proliferation, differentiation, apoptosis and autophagy, all of which are perfectly orchestrated and tightly regulated to remodel or restore the body pattern. While neoblast biology and body re-patterning are currently the subject of intense research, apoptosis and autophagy remain much less studied. In this review we will summarize our current understanding and hypotheses regarding where and when apoptosis and autophagy occur and fulfil an essential role in planarians.


Planarian Autophagy Apoptosis Cell death Regeneration Remodelling 



We apologize to the authors of research articles we could not cite due to space limitations. The authors would like to thank to D. Felix, Professor J. Baguñà and the anonymous reviewers for their valuable opinion and proofreading of the manuscript. We are also indebted to Dr M. Sefton for advice on the English style and for critical reading of the manuscript. This work was supported by grants BFU2005-00422 and BFU2008-01544 from the Ministerio de Educación y Ciencia (Spain) and grants 2005SGR00769 and 2009SGR1018 from AGAUR (Generalitat de Catalunya, Spain) to ES. CGE is funded by a Beatriu de Pinós fellowship (Generalitat de Catalunya, Spain) and an Anne McLaren fellowship (University of Nottingham, UK).


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Copyright information

© Springer Science+Business Media, LLC 2010

Authors and Affiliations

  1. 1.Institute of Genetics, Queen’s Medical CentreThe University of NottinghamNottinghamUK
  2. 2.Departament de Genètica, Institute of Biomedicine (IBUB)Universitat de BarcelonaBarcelonaSpain

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