Proportioning and regeneration in fissioned and unfissioned individuals of the planarian <i>Dugesia tigrina</i>

Abstract

Abstract Regeneration was examined in fissioned and unfissioned planarians ( Dugesia tigrina ) in terms of regenerative success and body proportioning. Regenerative success was determined in terms of percent of abnormal regenerates and number of abnormalities per abnormal regenerate. Sections from unfissioned animals were less successful at regeneration than were those from fissioned animals, and body regions located immediately behind the pharynx represented those segments which formed fewer abnormal regenerates as a result of fissioning. Body proportioning was measured as a function of size of head and prepharygeal region to overall body length. A direct correlation was seen in the proportional size of these two parameters, which varied significantly among regenerates. Results suggest that body proportioning is not constant from one excised piece to another but is predictable and dependent on several variables including interval between fission and sectioning, region from which the segment was obtained, and/or original length of the segment.