Flatworms & Maze Memory

[Krister Eriksson]

In article <32A905B4.4124 at stratos.net> Dave York <dyork at stratos.net> writes:

>Can anyone help me locate information on an experiment I vaguely recall 
>reading about years ago? Flatworms (?) were taught to execute a 2-D maze 
>then chopped up and fed to 2nd group of flatworms who were supposed to 
>acquire some knowledge about executing the maze. Hard to believe! Can't 
>understand what mechanism for environmental experience could be transmitted 
>in this manner. Have I lost my memory???

>Thanks in advance... 

I have to use my memory for this one, since I don´t have any references handy. 
Planarian flatworms were put in a T-maze and they were somehow (attracted by 
food or repelled by some noxious chemical? I can´t remember) "learned" to 
always turn in the same direction. If these animals had their heads cut off, 
the newly regenerated head still knew in which direction to turn. And if the 
trained animals were chopped up and fed to untrained animals, the knowledge 
was transferred to the untrained animals. I think that these results were 
taken as support for the in those days commonly(?) held hypothesis that RNA is 
the carrier of memory. 
However, I read a review paper in which the author stated that most of 
these studies failed to take a very important factor into consideration: slime.
The planarians give off mucus that forms a track in the same fashion as 
snails do. They also prefer mucus-covered areas over clean ones. Accordingly, 
the T-maze would soon have a mucus track in either direction, that could lead 
the worms to make the correct choice. My personal experience is that this 
mucus is insoluble in water and I once noted that it was still there after 
about one month in water containing washing detergent.

Regards,

Krister Eriksson
Dept. Biology
Åbo Akademi University
Åbo, Finland