MadSci Network: General Biology
Query:

Re: How important is the role of minerals in the regeneration of planarians?

Date: Wed Mar 28 04:41:09 2001
Posted By: shashank harithsa, Grad student, Research fellow in Microbiology department, National Institute of Oceanography
Area of science: General Biology
ID: 985369709.Gb
Message:

Dear  Narda,

Hi!, I have tried to answer your question. Hope you will be satisfied.  

Some basics:

Planaria (Dugesia) has great power of regeneration.   If it is cut into 
two, each part will form the lost portion.  A cut piece of moderate size 
from any part of the body will form a new worm.  Some pieces taken from 
posterior side form animals with reduced head or no head at all.  The 
ability of a piece to regenerate into a complete worm depends upon the 
regeneration of head at anterior cut surface, because the head controls 
the morphological pattern.  If sexually mature planarian is cut into two 
between the pharynx and the copulatory apparatus, then the reproductive 
organs degenerate, and each piece will regenerate into an asexual worm.  
Longitudinal cuts produce double heads or tails.

On cutting planarians, free cells from the mesenchyme called neoblasts 
migrate to the cut surface and give rise to a bud like structure called 
blastema which differentiate into the lost part.  In fact, two processes 
occurring together complete the process of regeneration.  These processes 
are epimorphosis, which is related to the formation of lost part, and 
morphollaxis, which is related to the adjustment and coordination between 
the old tissue and regenerated tissues.
Many organisms down the ladder of animal kingdom has the power of 
regeneration, for instance; earthworm and hydra. Some lizards can 
regenerate the lost tail.

The answer to your question is:

Yes, the presence of minerals is important for the regeneration since the 
animal has to build its cells and tissues.  It is also true that 
planarians can live without food for long periods, they obtain nourishment 
by dissolving their reproductive organs, parenchyma, and muscles, and they 
get smaller in size.  The missing parts are regenerated when they feed 
again.  Food consists of small living worms, crustaceans and snails and 
pieces of larger dead animals.   

Planarians die within a few days of being placed in distilled water. They 
will also die in relatively pure well water (Steve Sauter: 
sauter@massed.net).

For more information on planarians you can visit the web site: 
www.planarians.org

Shashank HARITHSA
March 28,2001



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