Planarian
The planarian Schmidtea mediterranea is a freshwater flatworm about a centimeter long and one of the most famous regenerators in biology. A piece cut from its body can regrow into a complete worm.
The planarian Schmidtea mediterranea is a freshwater flatworm about a centimeter long and one of the most famous regenerators in biology. A piece cut from its body can regrow into a complete worm.
🧬 Field Guide Specimen: Open Planarian in the CRV Science Field Guide to log the specimen, see its place among the Lophotrochozoa lineages in the Cladogram Explorer, and test your recall in the Red List conservation game.
Neoblasts: The Stem Cells That Rebuild
A large population of adult stem cells called neoblasts, making up a substantial share of the animal's cells, can give rise to every cell type. After injury, neoblasts migrate to the wound and rebuild missing tissues. In 1898 Thomas Hunt Morgan showed that a piece as small as 1/279th of a planarian can regrow into a worm.
Which End Is Head? Wnt Signals
Gradients of Wnt signaling along the body decide whether a fragment makes a head or a tail. Blocking the signal with RNA interference can produce two-headed animals, a classic experiment. See RNA interference.
Sex or Splitting
Some planarian strains reproduce sexually as hermaphrodites, while others divide by fission and regrow. The animal's simple two-eyed head, brain and gut make it a favorite for studying regeneration and stem-cell biology.
Planarian at a Glance
| Property | Value |
|---|---|
| Scientific name | Schmidtea mediterranea |
| Kingdom | Animalia |
| Phylum | Platyhelminthes |
| Class | Rhabditophora |
| Order | Tricladida |
| Family | Dugesiidae |
| Field Guide group | Lophotrochozoa: Worms, Shells & Allies |
| Diagnostic feature (Field Guide) | Legendary model for stem cell biology and bilateral tissue regeneration. |
| Phylum | Platyhelminthes |
| Famous experiment | Regrowth from 1/279th fragment (Morgan, 1898) |
See Also
- Stem cell biology and regenerative medicine — adult stem cells
- RNA interference — a tool for studying planarian genes