ACID AND ALKALINE PHOSPHATASE CHANGES ASSOCIATED WITH FEEDING, STARVATION AND REGENERATION IN PLANARIANS

¹ Department of Biology, Lynchburg College, Lynchburg, Virginia
² Department of Physiology, University of North Carolina, Chapel Hill, N. C.

1. The ingestion of cooked food by starved planarians is followed by the appearance of high levels of acid, and later of alkaline phosphatase activities in the gastrodermal cells. The enzyme activities decline gradually, to disappear after 7-10 days. Beginning about 4 days after feeding, the gut region is progressively invaded by neoblasts with high acid phosphatase activity. Intense alkaline phosphatase activity persists in certain "essential" structures (nerve fibers, gland cells protonephridia) even after periods of starvation as long as 60 days.

2. During regeneration following transection, neoblasts rich in acid phosphatase invade both the regenerating organs and the degenerating structures of the original segment. This represents enzyme induction, since resting neoblasts show no acid phosphatase activity. Neoblasts with alkaline phosphatase activity are abundant in the regions of regeneration, but the significance of this observation is uncertain since alkaline phosphatase activity also characterizes resting neoblasts.

3. It is suggested that the lysosomal acid hydrolases (typified by acid phosphatase) are involved not only in the early stages of digestion in the food vacuoles, but also in the autolysis of dispensable organs during starvation and in the tissue breakdown which precedes regeneration in transected planarians.