Capacidades de regeneração latente persistem após recente perda evolucionária em anelídeos assexuais

Latent regeneration abilities persist following recent evolutionary loss in asexual annelids

Alexandra E. Bely1 and James M. Sikes2

- Author Affiliations

Biology Department, University of Maryland, College Park, MD 20742
↵2 Present address: Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

Edited by Douglas Futuyma, Department of Ecology and Evolution, State University of New York, Stony Brook, NY, and approved November 5, 2009 (received for review July 15, 2009)

Abstract

Regeneration abilities have been repeatedly lost in many animal phyla. However, because regeneration research has focused almost exclusively on highly regenerative taxa or on comparisons between regenerating and nonregenerating taxa that are deeply diverged, virtually nothing is known about how regeneration loss occurs. Here, we show that, following a recent evolutionary loss of regeneration, regenerative abilities can remain latent and still be elicited. Using comparative regeneration experiments and a molecular phylogeny, we show that ancestral head regeneration abilities have been lost three times among naidine annelids, a group of small aquatic worms that typically reproduce asexually by fission. In all three lineages incapable of head regeneration, worms consistently seal the wound but fail to progress to the first stage of tissue replacement. However, despite this coarse-level convergence in regeneration loss, further investigation of two of these lineages reveals marked differences in how much of the regeneration machinery has been abolished. Most notably, in a species representing one of these two lineages, but not in a representative of the other, amputation within a narrow proliferative region that forms during fission can still elicit regeneration of an essentially normal head. Thus, the presence at the wound site of elements characteristic of actively growing tissues, such as activated stem cells or growth factors, may permit blocks to regeneration to be circumvented, allowing latent regeneration abilities to be manifested.

regeneration loss Annelida asexual reproduction evolution

Footnotes

1To whom correspondence should be addressed. E-mail: abely@umd.edu.

Author contributions: A.E.B. designed research; A.E.B. and J.M.S. performed research; A.E.B. analyzed data; A.E.B. wrote the paper.

The authors declare no conflict of interest.

This article is a PNAS Direct Submission.

This article contains supporting information online at www.pnas.org/cgi/content/full/0907931107/DCSupplemental.

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