Three species of the sea cucumber Holothuria parva, Holothuria arenicola and Holothuria leucospilota were identified from the tidal shores of the Bandar-e Deyr using calcareous spicules and the mitochondrial 16S rRNA gene. Sea cucumbers exhibit a high capacity for regeneration, such that, following the ejection of inner organs in a process called evisceration, the lost organs regenerate. During the evisceration in H. parva, most parts of the digestive tract and left respiratory tree were removed from the body. The esophagus, cloaca, right respiratory tree, and gonad remained in the body cavity. Regeneration of the digestive tract and respiratory tree was assessed using the hematoxylin-eosin staining technique for 75 days. First, the digestive tract and then the respiratory tree began to grow with a slightly late. Regeneration of the digestive tract extended from the esophagus to the cloaca (anterior-posterior). Regeneration began with the expansion of the mesentery attached to the esophagus, then cavities were created in this newly formed structure, and by merging them together, the gastrointestinal lumen was formed. The respiratory tree is made up of three main parts: the trunk, the branch, and the ampulla. The three layers of coelomic epithelium, connective tissue, and luminal epithelium are clearly recognizable in the structure of the respiratory tree. The replacement of lost anatomical structures is usually subdivided into three basic stages: initial (wound healing), regeneration, and growth. The growth of the regenerated respiratory tree in H. parva was very slow and no wrapping around the intestine was observed 75 days post evisceration. Measurement of oxidative stress after visceral extraction and during the regeneration process by measuring antioxidant enzymes (SOD and CAT) as well as MDA as an indicator of lipid peroxidation, showed an increase in oxidative stress in tissues (digestive tract, respiratory tree, and Muscle). Oxidative stress was reduced at th