Morphological Features and Temporary Characteristics of the Process of Muscle Tissue Regeneration in a Planarian Polycelis tenuis (Platyhelminthes)

The musculature of the body of a planarian Polycelis tenuis (Turbellaria, Platyhelminthes) was studied by fluorescence microscopy using histochemical staining of total preparations with fluorescently labeled phalloidin, which stains muscle cells due to irreversible binding to actin filaments. It was shown that the musculature of the body wall contains circular, diagonal and longitudinal muscle fibers. The circular fibers are the thinnest and most densely located in the outer layer of the musculature. The longitudinal fibers are thick, gathered in bundles. The individual diagonal muscle fibers are located at a significant distance, in two directions and at an angle to each other. The process of regeneration of muscle tissue in P. tenuis after resection of the head end of the animal was studied. Regeneration was assessed in dynamics; the animals were examined on days 3, 5, 7, 10, and 13 after surgery. Based on the results of microscopic examination, a conclusion was made about the main stages of muscle tissue regeneration and their characteristic features. It has been shown that the muscular system of P. tenuis has a high priority and regeneration rate; it is restored within 10–13 days.