The effect of starvation and re-feeding on mitochondrial potential in the midgut of Neocaridina davidi (Crustacea, Malacostraca)

The midgut in the freshwater shrimp Neocaridina davidi (previously named N. heteropoda) (Crustacea, Malacostraca) is composed of a tube-shaped intestine and a large hepatopancreas that is formed by numerous blind-ended tubules. The precise structure and ultrastructure of these regions were presented in our previous papers, while here we focused on the ultrastructural changes that occurred in the midgut epithelial cells (D-cells in the intestine, B- and F- cells in the hepatopancreas) after long-term starvation and re-feeding. We used transmission electron microscopy, light and confocal microscopes and flow cytometry to describe all of the changes that occurred due to the stressor with special emphasis on mitochondrial alterations. A quantitative assessment of cells with depolarized mitochondria helped us to establish whether there is a relationship between starvation, re-feeding and the inactivation/activation of mitochondria. The results of our studies showed that in the freshwater shrimp N. davidi that were analyzed, long-term starvation activates the degeneration of epithelial cells at the ultrastructural level and causes an increase of cells with depolarized (non-active) mitochondria. The process of re-feeding leads to the gradual regeneration of the cytoplasm of the midgut epithelial cells; however, these changes were observed at the ultrastructural level. Additionally, re-feeding causes the regeneration of mitochondrial ultrastructure. Therefore, we can state that the increase in the number of cells with polarized mitochondria occurs slowly and does not depend on ultrastructural alterations.淡水虾新米虾（Neocaridina davidi，曾用名N. heteropoda）隶属于甲壳纲（Crustacea）、软甲纲（Malacostraca），其体内的中肠由管状肠以及由大量盲端小管构成的大型肝胰腺组成。我们既往的研究已阐明了这两类组织的精细结构与超微结构，本文则聚焦于长期饥饿与复喂后，其中肠上皮细胞（肠内D细胞、肝胰腺内B细胞与F细胞）的超微结构变化。我们采用透射电子显微镜、光学显微镜、共聚焦显微镜与流式细胞术，全面描述了该胁迫因子诱导的各类细胞变化，并重点关注线粒体的结构改变。通过对线粒体去极化细胞的定量评估，我们明确了饥饿、复喂与线粒体失活/激活之间的关联。研究结果显示，在所分析的新米虾个体中，长期饥饿会在超微结构层面诱导上皮细胞发生退变，并使携带去极化（无活性）线粒体的细胞比例上升。复喂过程可逐步实现中肠上皮细胞细胞质的再生，但这类变化仅能通过超微结构观测到。此外，复喂还可促进线粒体超微结构的修复重建。综上，我们认为携带极化（活性）线粒体的细胞数量恢复过程较为缓慢，且与细胞超微结构的改变并无关联。