Cells are the basic structural, functional and biological units of all known living organisms. Cells have incredible capabilities – consider how you grew from a single cell or how your body heals from injury!

Some parts of our bodies can repair themselves quite well, but others don’t repair at all. We certainly cannot regrow a whole leg or arm, but some animals CAN regrow – or regenerate – whole body parts.  So what can we learn from these regenerative animals?

The common examples of regeneration include lizards who grow back a lost or damaged tail, lobsters who grow back a lost claw, and spiders who grow back a lost leg.

However, there is one particular animal species that possesses almost unlimited regenerative capacities. It is a special type of flatworm called Planarian, which can be cut in half, again and again hundreds of times, and each half grows back into a full worm.  These flatworms are freshwater invertebrates that have been a classic regeneration model for over a century.

Research by The Reddien Lab found that following the decapitation of planarians, “a new head can be regenerated in under a week and an entire animal can be regenerated from a body fragment approximately 1/300th the size of the original animal.”

So how does this happen?


Planarians are bilaterally symmetric metazoans, which have cephalic ganglia (brain), two ventral nerve cords, and many sensory neurons. Planarian regeneration involves the formation of an outgrowth of tissue at wound sites (a blastema) that produces missing tissues. In essence, the entire nervous system is regenerated!

What is even more incredible is that 50% of the planarian genes that have been examined contain human counterparts, meaning that planarians are “excellent organisms for in vivo studies of how stem cells can be regulated to replace aged, damaged, and missing tissues.”

Who would have thought that this flatworm species could be so integral to our understanding of human stem cell biology!

What about plant cells?

They also have regenerative capabilities … consider a frangipani tree. If you take a limb from a frangipani tree and put it in soil, it will grow into another thriving tree.

So how different are plant and animal cells? What factors distinguish one from the other?

Discover with IntoScience

With IntoScience, students can explore the differences between plant and animal cells. Student understanding is enhanced through interactive activities, ensuring a comprehensive understanding on completion of the ‘Comparing plant and animal cells’ activity.


Source: The Reddien Lab: MIT Department of Biology

Photo Credit: The Reddien Lab: MIT Department of Biology