The Growth-Promoting Power of Egg for Planarian Worms

Abstract

It has been previously demonstrated by us 1 that an exclusive diet of egg albumin is not capable of promoting growth in Planaria maculata. Although the food is well taken, the worms show progressive decrease in size throughout the experimental period. Upon an exclusive diet of egg yolk the worms may maintain or increase their size for a period of 2 or 3 weeks, but after that time their length becomes progressively less.

We have confirmed these results repeatedly with the species of planarian worm (Planaria agilis?) which we are at present using, and have found in addition that a combination of egg yolk with egg albumin produces a diet decidedly superior to either substance used alone.

Each group in an experimental series consisted of 30 worms of equivalent size which were fed ad lib. twice a week on the experimental diets. The total length of the worms was found at the beginning of the experiment and at its conclusion and the proportional increase in length was determined. In one experiment of 2 weeks duration kept at room temperature, the group of 30 worms fed upon egg yolk made a gain in total length of 3.9%, while those fed upon a combination of equal parts of egg yolk and albumin gained 20.2% in total length. In another series incubated at a temperature of 27° C. over a 2 week period, egg yolk diet produced an increase in total length of 32%, while a diet of blended egg yolk and albumin in equal parts gave an increase in total length of 51.5%. In a third series pastes were made of 15% liver pulp and 45% starch paste (10%) with the addition of 40% egg yolk or egg albumin or a mixture of equal parts egg yolk and albumin.