Planaria Investigation

[Erin Nash]

Using cell division as the overall theme, develop a question to answer in reference to how cell division is different (or similar to) organisms that cannot asexually reproduce.

Overarching question - How is cell division different in organisms that reproduce asexually? (Or...is it different at all?)


A few others to consider -

A planaria can regenerate half of its body. A starfish can regenerate a lost limb. Is the process similar in the two creatures, or different?

Why can't humans regrow lost limbs?

In your answer, make sure to post your question, as well as a response to that question.

[Kylie Warner]

My questions are: What programs them to know to grow back a limb and what do they do in the mean time of growing them back?

[Kylie Warner]

Alright so.. the answers to my questions weren't so easy to find. There's not a definant answer to how a planrian knows to just grow back a limb, or the right one at that. But when it loses a tail or head, the regeneration process kicks in and the cells divide to create something new.

As for the "In the mean time question..." the closest answer I came to was they just wait. The head or tail takes around two weeks to grow back.

It's a difficult understanding for sure.

[Ally S]

How do growing tails of planaria eat?

Well, I found a great site that can explain it.

This website tells you that when planaria split and are tails, they feed off of themselves!
Crazy, right?
:)
Check it out for more info. I think there's some pictures on there, too. Click on the link that says, "Next: How Do They Do It?" at the bottom, too! O.o

[Marcy Withrow]

Can planaria starve and die?

I found out that when planaria starve, they start to shrink! Planaria start to loose their cells from starving. They don't lose their form or function, they only lose cells. They also move faster when staring. As for dying, I couldn't find much on that. I suppose if you would starve them long enough they would die, if they just kept loosing cells. When researching websites I came upon the phrase "uneaten food will foul the water and the planaria will die." Which makes since, on a count of planarians are carnivores. I'm sure rotten liver wouldn't be too healthy.

This leads back to cell division, because the cells are dying. So, wouldn't cell division almost be decreasing? Or at least slowing down? Usually when cells die new ones take their place. But, in this case, the planarians are decreasing in size. Doesn't that mean there are no new cells to take it's place? I would love for these questions to be answered, I just couldn't find the right information to answer them.

Here are my links. This is the first one i found.
This is the second, it talks about starvation and the effect on their moving rate. It's really bulky, just scroll to the bottom of it all and there is a summary. It sums it up. (:

[Ivory Baldwin]

Okay My Question was.. how does planarias one tract digestive system work if its split in half when they regenerate??

Planaria have only one hole for food and that same hole is also where their waste comes out of, its called pharynx. The pharynx is located on the under side of the flat worms in the center of their bodies. Sense they split in the middle of their bodies the pharynx gets split in half and a regeneron blastema will form where the wound is. This area of whitish cells are filled with stem cells that will end up diffeentiat of the missing part can grow. But I was wondering how they would eat sense they didnt have the pharynx yet, well i learned that the flat worm feed off themselves and some of the cells in each regrowning flat worm will self destruct and give energy so that the regrowing flat worm can survive until its big enough to survive on its own.

The website i used was called Microscope Imaging Station. There are some videos of planaria regeneration CHECK THEM OUT, my computer wouldnt let me :(

[Taylor Woodruff]

How are planaria and human genes similar and different?

There's a gene that both human's and planaria's share, but in a way they are completely different because it's the way we regenerate. The planaria's have what's called a "piwi" which is how they create stem cells allowing them to regenerate themselves. While Human's ahve what's called a "hiwi" which is in sperm and eggs, and we all know that we need a sperm and an egg to regenerate!

...now scientists are trying to find a way to to trigger our stem cells to be able to regenerate lost limbs. But, the question is...will we ever find out how to actually do it?

[Terra Younger]

Can planaria be spilt both ways (down the center & across the body) and still regenerate correctly?

[Blayr Bolton]

Looking at a planaria and seeing it can regrow lost limbs is phenomenal to even think about, but why can't humans regrow lost limbs? I'll tell you...

The planaria, starfish, and salamander all have the ability to regrow lost limbs, but why? It's because they possess progenitor cells that allow for regeneration to occur. Progenitor cells go through elaborated processes such as de-differentiation and then specialisation. The interesting part about this is that we do have progenitor cells for our skin and liver, but other places lack the progenitor cells. And that's why limbs, or for that matter, any other human part, can't regenerate or regrow lost limbs. Scientists indeed are doing research about Stem Cells to try and help people regrow lost, amputated, or diseased parts. Now what would life be like if that could really happen...

[Aziz Siddikov]

Is there is limit, when we can not cut any more?


The tail can be cut crosswise into three or four and they will all regenerate a head. Note that the head is regenerated first before tail elongation occurs

[Shelby Hawkins]

My original question posted Friday was "Do different species of Planaria regenerate in different ways and different speeds?"

I am having trouble finding the answer to that, but I did come across a really cool experiment done with planarian in 1955 that reminded me of our discussion about training planaria. The experiment was set up by flashing a bright light and shocking planarian at the same time as the flash. After many times of doing this, the experimenters took away the shocking element. However, the planaria still reacted to the flash of light as if they had been shocked. These trained worms were then split and regenerated. The new regenerated worms also had the same reaction to light. This experiment was repeated later, except planaria were fed ground up into small pieces and fed to other planaria. It was claimed that these new worms had the ability to train and learn much faster, suggesting that memory could be transfered chemically.

However, when this experiment was repeated with other animals the same results were not produced. Some researchers say that the data was biased. As with science, nothing is ever proven or disproven but this seems highly unlikely.

This whole situation reminded me a lot of our discussions at the beginning of the year about the scientific method and how theories are "proven."

[Kerstyn Bolton]

My question is have we ever been able to regenerate limbs?

First of all, I was just researching and found at that at some extent all species can regenerate, but depending on how evolved the species is a big factor. The more the evolved the less likely chance of regeneration. If you really think about it we do regenerate lost skin and bone tissue, which is along the same lines as the planaria and starfish. Our skin cells also fall off, so they have to grow back through mitosis which would be considered regeneration right? I also just read about how the salamander has a clump of cells called the blastema form at the tip of a limb and they can produce skin, muscle, bone, blood vessels and neurons. Therefore, it would ultimately regrow the limb. Right now researchers are trying to develop a connection to this and then the limbs of humans, which we know wouldn't happen for a long time, but the fact that the research could be there is really exciting! From what I've read we have not been able to regenerate limbs in our lifetime, which makes me question the evolution statement because I would think at some point in time we should've been able to.

[Laci Shoemaker]

Is there a certain way you can cut them to where they will die & not reproduce?