Morphological mechanism allowing a parasitic leech, Ozobranchus jantseanus (Rhynchobdellida: Ozobranchidae), to survive in ultra-low temperatures.
Morphological mechanism allowing a parasitic leech, Ozobranchus jantseanus (Rhynchobdellida: Ozobranchidae), to survive in ultra-low temperatures.
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DOI：
10.1242/bio.058524
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发表时间：
2021-07-15
期刊：
影响因子：
2.4
通讯作者：
Nie L
中科院分区：
文献类型：
--
作者：
Gu S;Liu J;Xiong L;Dong J;Sun E;Hu H;Yang M;Nie L
Ozobranchus jantseanus 是迄今为止已知无需预处理即可在液氮中生存的最大后生动物；然而，这种耐受性背后的机制仍不清楚。在这项研究中，首次分析了正常、冷冻和脱水状态下的组织学和形态学变化。成虫直接置于液氮中96 h后成活，成活率约为86.7%。水蛭能承受快速干燥，当失水量低于84.8%时，补水后成活率为100%。经过冷冻、干燥、乙醇脱水后，水蛭立即形成半球形。特别是在干燥过程中，在表面观察到明显的透明玻璃状物质。扫描电镜显示后吸盘表面有许多孔隙，形成海绵状结构，有助于快速排出水分，半球形的形状可以通过前后方向的收缩和折叠重建来保护内脏器官。表面大量的粘多糖以及体内的酸性细胞和胶原纤维都含有大量的多糖，可能在冷冻过程中发挥关键的保护作用。我们的结果表明，水蛭对超低温的抵抗力可以通过冷冻保护脱水/玻璃化策略来解释。 摘要： 首次从形态学角度研究了最大的无需预处理即可在超低温下生存的后生动物Ozobranchus jantseanus的耐冻机制。
Ozobranchus jantseanus is the largest metazoan known to survive in liquid nitrogen without pretreatment to date; however, the mechanism underlying this tolerance remains unclear. In this study, the first analyses of histological and morphological changes in normal, frozen, and dehydrated states were performed. Adults survived after direct placement in liquid nitrogen for 96 h, with a survival rate of approximately 86.7%. The leech could withstand rapid desiccation and its survival rate after rehydration was 100% when its water loss was below about 84.8%. After freezing, desiccation, and ethanol dehydration, the leech immediately formed a hemispherical shape. Particularly during drying, an obvious transparent glass-like substance was observed on surface. Scanning electron microscopy revealed many pores on the surface of the posterior sucker, creating a sponge-like structure, which may help to rapidly expel water, and a hemispherical shape may protect the internal organs by contraction and folding reconstruction in the anterior–posterior direction. A substantial amount of mucopolysaccharides on the surface and acid cells and collagen fibers in the body, all of which contained substantial polysaccharides, may play a key protective role during freezing. Our results indicate that the resistance of leeches to ultra-low temperatures can be explained by cryoprotective dehydration/vitrification strategies. Summary: The freeze tolerance mechanism of Ozobranchus jantseanus, the largest metazoan animal requiring no pretreatment that can survive in ultra-low temperature, was first studied from the perspective of morphology.