Eisapour Mina, Salamat Negin, Salari Mohammad Ali, Bahabadi Mahmoud Nafisi, Salati Amir Parviz
Department of Marine Biology, Faculty of Marine Sciences, Khorramshahr University of Marine Science and Technology, Khorramshahr, Iran.
Department of Fisheries and Biology, Persian Gulf Research Institute, Persian Gulf University, Bushehr, Iran.
J Exp Zool B Mol Dev Evol. 2022 May;338(3):155-169. doi: 10.1002/jez.b.23109. Epub 2021 Nov 23.
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 trend in the eviscerated animals during the experiment. However, its value reduced to the control level at the end of the experiment.
呼吸树仅存在于海参纲中，而其他棘皮动物则没有。只有一些海参种类具有在自切后再生其呼吸树的能力。因此，呼吸树可被视为评估动物再生机制的合适模型。在本研究中，对小海参（Holothuria parva）后肠切除术后75天内的呼吸树再生情况进行了检查。由于自切会降低生物体中的抗氧化防御能力，因此在本研究中还评估了实验期间抗氧化酶的变化。小海参是分布在波斯湾北部的主要潮间带物种。在本研究中，小海参在注射氯化钾后约1 - 2分钟，从肛门排出左呼吸树、消化道和支持性肠系膜。身体后端开口的闭合是对损伤的第一反应。后肠切除术后7天，泄殖腔背侧形成小芽，被泄殖腔的体腔上皮覆盖。体腔上皮开始增殖为芽顶端的未分化细胞。初级呼吸树由管腔立方上皮和被细长体腔上皮包围的薄结缔组织组成。这个初步的器官在切除术后13天在芽的顶端被观察到。逐渐地，肌上皮细胞围绕纵轴排列并形成环形肌肉。初级呼吸树的原始分支在切除术后18天开始形成。切除术后40天，呼吸树的管腔上皮与完整的管腔上皮外观相同。切除术后56天，再生的呼吸树在组织形态学上与完整的呼吸树非常相似，但与之不同的是，它尚未包裹在肠道周围，而是与肠道完全分离。尽管再生呼吸树在发育，但直到实验结束都未观察到其围绕肠道的情况。根据结果，切除术后5天，肌肉匀浆中过氧化氢酶（CAT）和超氧化物歧化酶（SOD）的活性显著高于对照组。切除术后动物体内的CAT和SOD水平逐渐下降。在实验过程中，切除术后动物体内的脂质过氧化水平呈下降趋势。然而，其值在实验结束时降至对照水平。
