EFFECT OF TIMING OF CUTTING ON PATTERNING AND PROPORTION REGULATION DURING REGENERATION OF THE PLANARIAN DUGESIA-TIGRINA

The time interval between cuts that are made to obtain a tissue fragment from a planarian was found to be important to the process of its regeneration. Short fragments made by two transverse cuts across the body were more likely to regenerate abnormally when the interval between the two cuts was 5 or 12 min than when it was 1.5 min. The longer intervals specifically altered the regression line in the correlation between the length:width ratio of fragments and frequency of abnormal regenerates. This effect occurred regardless of which region of the body the fragment was taken from. The time interval also affected body proportioning in regenerates and to the greatest degree in fragments derived from the region located immediately behind the head. These results indicate that events occurring shortly after a cut is made in a planarian significantly affect structure patterning and proportioning of the regenerate.