Zhu Diao, Wang Xiao-Yun, Liu Lu, Tong Xin
Guangxi Key Laboratory of Agro-Environment and Agric-Products Safety, National Demonstration Center for Experimental Plant Science Education, College of Agriculture, Guangxi University, Nanning, Guangxi, 530004, China.
School of Life and Environmental Sciences, Key Lab Wildlife Evolut & Conservat Mt Ecosyst Gua, Nanning Normal University, Nanning, Guangxi, 530100, China.
Protoplasma. 2025 Sep 3. doi: 10.1007/s00709-025-02108-3.
The midgut of insects originates from the endoderm. It is located in the central part of the digestive tract and serves as the primary site for chemical digestion and nutrient absorption. The larvae of Cerambycidae are the most destructive life stage. However, the ultrastructure of the larval midgut has been reported in only a few cerambycid groups. This study employs light, scanning electron, and transmission electron microscopy to observe the midgut ultrastructure of the Rhytidodera bowringii White, 1853 larvae. From outside to inside, the midgut of R. bowringii consists of a muscle layer, a basal membrane, an epithelium, and a lumen. The external muscles of the midgut are arranged in an outer longitudinal muscle and inner circular muscle. The epithelial tissue mainly comprises two types of cells: digestive cells and regenerative cells. The arrangement of regenerative cells in the midgut forms nidi, where multiple cells cluster together. The nucleus occupies most of the cytoplasm, which contains only a small number of organelles. The basal plasma membrane of the midgut epithelial cells is conspicuously infolded in R. bowringii, and around the nucleus, with a large amount of rough endoplasmic reticulum. At the apical regions of these digestive cells, numerous tightly arranged microvilli and mitochondria can be observed and many vesicles are localized near the lumen. This indicates that the digestive cells in the midgut have a strong secretory activity of digestive enzymes and other proteins, which may facilitate the larvae of the cerambycid in digesting recalcitrant plant tissues. It is the first time that the ultrastructure of the midgut of the R. bowringii larvae has been studied. The results can provide foundational insights into the ultrastructural organization of the Cerambycidae larval digestive system and the toxic mechanisms underlying prevention strategies for this pest.
昆虫的中肠起源于内胚层。它位于消化道的中央部分，是化学消化和营养吸收的主要部位。天牛幼虫是最具破坏力的生命阶段。然而，仅在少数天牛类群中报道过幼虫中肠的超微结构。本研究采用光学显微镜、扫描电子显微镜和透射电子显微镜观察了1853年命名的白星天牛幼虫的中肠超微结构。从外到内，白星天牛的中肠由肌肉层、基膜、上皮和肠腔组成。中肠的外部肌肉由外层纵肌和内层环肌组成。上皮组织主要包括两种类型的细胞：消化细胞和再生细胞。中肠中再生细胞的排列形成巢，多个细胞聚集在一起。细胞核占据了大部分细胞质，细胞质中仅含有少量细胞器。白星天牛中肠上皮细胞的基底质膜明显内陷，在细胞核周围有大量粗面内质网。在这些消化细胞的顶端区域，可以观察到许多紧密排列的微绒毛和线粒体，并且许多小泡位于肠腔附近。这表明中肠中的消化细胞具有很强的消化酶和其他蛋白质的分泌活性，这可能有助于天牛幼虫消化顽固的植物组织。这是首次对白星天牛幼虫中肠的超微结构进行研究。研究结果可为天牛幼虫消化系统的超微结构组织以及该害虫防治策略的潜在毒性机制提供基础见解。
