THE EFFECT OF COLCHICINE ON RECONSTITUTIONAL DEVELOPMENT IN DUGESIA DOROTOCEPHALA

Abstract

1. Colchicine was shown to inhibit regeneration in pieces of Dugesia dorotocephla. In addition it was shown to inhibit regulation to normal form.2. Within certain limits of concentration, the inhibitory effects of colchicine were reversible. Two to three weeks after return to water pieces from all levels developed normal heads (some with supernumerary eyes). Thus, through the use of colchicine it was possible to obliterate the head frequency gradient characteristic of this species.3. While colchicine was found to exert a marked inhibition of blastema formation in the reconstitution of planarian pieces it did not have the same effect on eye-spot differentiation. Pieces treated with higher concentrations of the agent failed to show any new tissue at the anterior and posterior cut surfaces by 10 days after section. Eye-spots, however, differentiated beneath the covering epithelium in anterior pieces.4. Heteromorphic forms with 3-4 heads developed from pieces taken from whole animals exposed to colchicine. This indicates that the medio-lateral differential was reduced subsequent to colchicine treatment and that the two lateral halves of the piece underwent independent differentiation.5. With the use of colchicine evidence was obtained that the 4th day of reconstitution represents a critical period in development. That is, pieces treated with M/5,000 colchicine for 4 days, and then returned to water, showed more inhibition than pieces treated for 3 or 5 days.