MadSci Network: General Biology |
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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