MELATONIN STIMULATES PHOTORECEPTOR DIFFERENTIATION IN REGENERATION OF PLANARIAN SCHMIDTEA MEDITERRANEA

The planarian Schmidtea mediterranea (Turbellaria, Platyhelminthes) has a pair of eyes on the anterior part of the body consisting of pigment cells and photoreceptor neurons capable of regeneration. The research represents a study of the effects of melatonin on photoreceptor differentiation after decapitation of the planarian. During the experiment, the worms were decapitated, and the eye regeneration was observed at days 3 and 4 of the regeneration. Different stages of the photoreceptor regeneration were observed such as both eyes in the regenerating planarians, planarians with one eye, and planarians with no eyes. In most of the animals, the photoreceptors were already visible at day 4 after the decapitation. In the experimental planarians exposed to melatonin at concentrations of 1 and 0.1 µM, the accelerated photoreceptor differentiation was observed. The stimulating effects of melatonin were detected in three animal groups on day 3 and 4 after the decapitation. The study will be continued to evaluate mechanisms of the melatonin action on planarian regeneration.