Muscle regeneration in holothurians

Abstract

The muscle system of holothurians includes visceral (coelomic epithelium) and somatic (longitudinal muscle bands, retractors of aquapharyngeal complex) musculature. Visceral musculature regeneration is achieved by the transformation of myoepithelial cells via their dedifferentiation, migration, proliferation, and redifferentiation. During somatic muscle regeneration the new muscle bundles are formed due to dedifferentiation, migration, and immersion of the coelomic epithelial cells into the connective tissue. While submerging, the epithelial cells transform into myocytes and begin to produce myofibrils in their cytoplasm. Concomitantly, a basal lamina is formed around the group of myogenic cells, separating them from the surrounding extracellular matrix. The myohistogenesis is accompanied by a conspicuous DNA-synthetic activity. Proliferation is insignificant and seems to be of no essential importance for muscle regeneration. The synthesis of DNA followed by no cytokinesis results in an increase in the amount of DNA of myocyte nuclei.

Post-autotomy regeneration of respiratory trees in the holothurian Apostichopus japonicus (Holothuroidea, Aspidochirotida)

“…The respiratory trees and gut of these animals are expelled during evisceration. Although there are several descriptions of gut regeneration after evisceration (see reviews by Dolmatov 1999;García-Arrarás and Greenberg 2001;Dolmatov and Mashanov 2007;Dolmatov 2009), regeneration of the respiratory trees has been neglected. Previously, we have provided a brief description of the structure and regeneration of the respiratory trees in Apostichopus japonicus Dolmatov 2001, 2003).…”

“…Most holothurians (apart from Apodida) have respiratory trees, which are specialised respiratory organs that evolved in the Holothuroidea and are absent in other echinoderms. Some holothurian species can regenerate the respiratory trees after their complete expulsion (Spirina and Dolmatov 2003;Dolmatov and Mashanov 2007). For this reason, these organs provide a model system that is suitable for the investigation of various problems of regeneration theory, including the mechanisms by which regenerative ability arose de novo in phylogenesis.…”

“…Together with hemichordates, they form the basal taxon Deuterostomia. Many echinoderms have the capacity to regenerate various organs efficiently (Dolmatov 1999;Dolmatov and Mashanov 2007). They can repair small appendages, such as tube feet, spines, feeding tentacles and pedicellariae, heal skin wounds, and regenerate after incision into, or ablation of, significant body parts.…”

“…In comparison with other echinoderm classes, holothurians show the most diverse regenerative capacity (Dolmatov and Mashanov 2007). Most holothurians (apart from Apodida) have respiratory trees, which are specialised respiratory organs that evolved in the Holothuroidea and are absent in other echinoderms.…”

“…Of the holothurians investigated, only species of the order Aspidochirotida can regenerate their respiratory trees (Dolmatov and Mashanov 2007). The respiratory trees and gut of these animals are expelled during evisceration.…”