Biology : planaria

INTRO - RESOURCES - LINKS

I N T R O D U C T I O N
 


The planaria encountered in the biology classroom are free-living flatworms famous for their ability to regenerate and to reproduce asexually through a process called fission. In fact not all species of planaria can regenerate, and those that cannot usually reproduce sexually, rather than asexually.

My past research has focused on the ecological and developmental factors which contribute to these varied life styles.

"If regeneration evolved--and it must have, because we see it today--the question is: was regeneration itself the trait that was selected for, or was it the byproduct of some other suite of traits? A simple starting point would be to examine the natural variation in the ability to regenerate. If population and species were invariant with respect to regeneration (that is, if they all regenerated in the same way), you couldn't have natural selection, which must act on a variable population. I took advantage of the fact that planarians regenerate to do genetics with them... Planarians have five different modes of reproduction; three modes are asexual and two are sexual. All modes do not occur in every species. An evolution of this degree of life-cycle variation interests me."

-Anne Fausto-Sterling, from Journeys of Women in Science & Engineering

R E S O U R C E S

 

Two laboratories, one directed by Alejandro Sanchez Alvorado and the other by Phil Newmark, have championed, once again and with spectacular success, the use of planaria as an organism worthy of study by developmental biologists.

Alejandro Sánchez Alvarado (2006) Planarian Regeneration: Its End is Its Beginning Cell. 124 (2):241-5.

Peter W. Reddien, Adam L. Bermange, Kenneth J. Murfitt, Joya R. Jennings and Alejandro Sánchez Alvarado (2005) Identification of Genes Needed for Regeneration, Stem Cell Function, and Tissue Homeostasis by Systematic Perturbation in Planarians Developmental Cell. 8:635-649.

Phillip A. Newmark, Peter W. Reddien, Francesco Cebri and Alejandro Sánchez Alvarado (2003) Ingestion of bacterially expressed double-stranded RNA inhibits gene expression in planarians Proceedings of the National Academy of Sciences USA. 100 (Suppl 1): 11861-5.

Alejandro Sánchez Alvarado (2003) The freshwater planarian Schmidtea mediterranea: embryogenesis, stem cells and regeneration Current Opinion in Genetics and Development. 13:438444. (Planarian Laying Egg Movie)

Nestor J. Oviedo, Phillip A. Newmark, and Alejandro Sánchez Alvarado (2003) Allometric Scaling and Proportion Regulation in the Freshwater Planarian Schmidtea mediterranea Developmental Dynamics. 226:326333

Alejandro Sánchez Alvarado, Phillip A. Newmark, Sofia M. C. Robb and Réjeanne Juste (2002) The Schmidtea mediterranea database as a molecular resource for studying platyhelminthes, stem cells and regeneration Development. 129:5659-5665.

For more on developmental variability in planaria see:

Ellis, Charles Jr. and Fausto-Sterling, Anne. (1997) "Platyhelminthes: the flatworms" in Embryology: Constructing the Organism. eds. Gilbert, Scott F. and Raunio, Anne M. (Sunderland: Sinauer)

For more on planaria in general see chapters 9-11 of:

Buchsbaum, Ralph, Buchsbaum, Mildred, Pearse, John and Pearse, Vicki (1987). Animals without Backbones, 3rd edition. (Chicago: University of Chicago Press).

 

L I N K S
 

The Sanchez Laboratory
Regeneration research. A long-standing problem of biology, regeneration in metazoans still awaits a satisfactory mechanistic explanation. Our laboratory's goal is to identify and to study the molecular components underpinning this phenomenon. We are approaching this problem by analyzing and manipulating the regenerative properties of an invertebrate organism, chiefly the freshwater planarian Schmidtea mediterranea.

The Newmark Lab
Department of Cell & Structural Biology
University of Illinois at Urbana-Champaign. We use freshwater planarians as models to study the molecular basis of regeneration. Work in my lab focuses on three general areas: Stem cell regulation, Germ cell development, Nervous system regeneration.

Phylum Platyhelminthes A description of flatworms. Flatworms are unsegmented, bilaterally symmetrical worms that lack a coelom (acoelomate) but that do have three germ layers.

Class Turbellaria Site includes Introduction, Life History
Habitat and distribution, Selected characteristics of commonly recognized turbellarian orders and suborders occurring in freshwaters, Feeding and functional role in the ecosystem, Indicator value, References and web URLs.

Introduction to the Platyhelminthes The simplest animals that are bilaterally symmetrical and triploblastic (composed of three fundamental cell layers) are the Platyhelminthes, the flatworms.

Brown University // Providence, Rhode Island 02912 // 401.863.1000
Last update: 8/20/2007