Myosin heavy chain gene in Dugesia (G.) tigrina: a tool for studying muscle regeneration in planarians

In most organisms the main body axes are specified during embryonic development.However, in freshwater planarian Dugesia (G,) ligrina (Platyhelminlhes, Turbellaria) the body axes musl be continuously re-specified in the adult period (Bueno et ai" 1996a) due to the 9reat morphol09ical plasticity shown by these organisms.Planarians can grow or degrow in a continuous manner depending on food availability and temperature, and they can regenerate a new organism from a small piece of its body (Romero & Baguna, 1988).During regeneration three basic processes must occur: a) a redefinition of the body pattern to establish the territories where the missing structures will appear; b) stem cells called neoblasts (Brondsted, 1969) proliferate and differentiate into all the cellular types necessary to form the missing structures; and c) these "de novo" cells become properly arranged in time and space to restitute the original body pattern.One possible way to study how these