Motility recovery during the process of regeneration in freshwater planarians

Planarians are phylogenetically considered to be the most primitive animals to have acquired a central nervous system and a bilateral symmetry. However, very little is known about the relationship between planarian brain integration and motility. A behavioural and histological study was therefore undertaken in an aspect of planarian motility recovery during its process of regeneration. Quantitative analysis showed that the tail-regenerates recovered their motility gradually as the new heads reformed, while the non-head reforming tail fragments showed no signs of recovery. The head fragments recovered their motility soon after cutting. The cephalic margin was not a function of the motility. The brain regenerated back to its original form in approximately two weeks, the same amount of time it took for the decapitated tails to recover their motility to initial levels. This study provides quantitative evidence that the planarian motility recovered in relation to the head formation during its process of regeneration. Our results reinforce the view that the brain plays a functional part in activating planarian motility.