Post‐autotomy regeneration of respiratory tree in sea cucumber Holothuria parva

Abstract

The respiratory trees present only in the class Holothuroidea and the rest of the echinoderms lack it. Only some holothurian species have the ability to regenerate their respiratory trees after autotomy. Therefore, respiratory trees could be considered as a suitable model to assess the regeneration mechanisms in animals. In the present study, the respiratory tree regeneration after posterior evisceration were examined in Holothuria parva during 75 days. Since autotomy reduces antioxidant defense in the organisms, in the present study alterations of antioxidant enzymes were also evaluated during the experiment. H. parva is the dominant intertidal species distributed in the north of the Persian Gulf. In the present study, H. parva ejected the left respiratory tree, the digestive tract and supportive mesenteries from the anus, about 1-2 min after potassium chloride injection. The closure of the opening at the posterior ends of the body was the first reaction to the injury. Seven days after evisceration, the small bud formed on the dorsal side of the cloaca which was covered with the coelomic epithelium of cloaca. The coelomic epithelium started to proliferate to undifferentiated cells on the apex of the buds.The primary respiratory tree consisted of the luminal cuboidal epithelium and thin connective tissue surrounded by the slender coelomic epithelium. This preliminary organ was observed at the apex of the buds, 13 days after evisceration. Gradually, myoepithelial cells arranged around a longitudinal axis and formed a circular muscle.The primitive branches of primary respiratory tree started to form 18 days after evisceration. Forty days after evisceration, the luminal epithelium of the respiratory tree had the same appearance as the intact luminal epithelium. The regenerated respiratory tree was histomorphologically very similar to an intact respiratory tree 56 days postevisceration, but unlike that, it was not yet wrapped around the intestine and was completely separate from it. Despite the development of the regenerating respiratory tree, no wrapping around the intestine was observed until the end of the experiment. According to the results, the activity of the catalase (CAT) and superoxide dismutase (SOD) in the muscle homogenate was significantly higher than the control 5 days after evisceration. The CAT and SOD levels gradually decreased in eviscerated animals. The lipid peroxidation level followed a decreasing

Transcriptomic analysis reveals the early body wall regeneration mechanism of the sea cucumber Holothuria leucospilota after artificially induced transverse fission

“…When faced with stressful situations, they have the remarkable ability to expel certain internal organs and subsequently regenerate the lost ones [ 12 ]. Recent studies regarding sea cucumber regeneration have primarily focused on the renewal process of diverse organs, including the intestinal tract [ 13 , 14 ], respiratory tree [ 15 ], body wall [ 16 ], and tube foot [ 17 ]. The body wall tissue of a sea cucumber comprises an epithelial layer, connective tissue layer, muscle layer, and coelomic epithelial layer [ 16 ].…”

Isolation of Extracellular Vesicles of Holothuria (Sea Cucumber Eupentacta fraudatrix)

“…The mechanisms of regeneration in holothurians are unclear; however, based on current knowledge about the regulation of life processes in mammals, they must be multicomponent. Published studies on the mechanisms of regeneration mainly concern molecular aspects, gene expression, and changes in tissues and organs [ 10 , 17 , 22 , 23 , 24 ]; while the possible role of EVs in the implementation of the regeneration process has not been studied. To fill the gap, we first decided to determine whether exosomes and other EVs are present in holothuria Eupentacta fraudatrix and could be isolated.…”