Data_Sheet_2_Structural and Functional Characterization of Hermetia illucens Larval Midgut.PDF

The larvae of Hermetia illucens are among the most promising agents for the bioconversion of low-quality biomass, such as organic waste, into sustainable and nutritionally valuable proteins for the production of animal feed. Despite the great interest in this insect, the current literature provides information limited to the optimization of rearing methods for H. illucens larvae, with particular focus on their efficiency in transforming different types of waste and their nutritional composition in terms of suitability for feed production. Surprisingly, H. illucens biology has been neglected and a deep understanding of the morphofunctional properties of the larval midgut, the key organ that determines the extraordinary dietary plasticity of this insect, has been completely overlooked. The present study aims to fill this gap of knowledge. Our results demonstrate that the larval midgut is composed of distinct anatomical regions with different luminal pH and specific morphofunctional features. The midgut epithelium is formed by different cell types that are involved in nutrient digestion and absorption, acidification of the lumen of the middle region, endocrine regulation, and growth of the epithelium. A detailed characterization of the activity of enzymes involved in nutrient digestion and their mRNA expression levels reveals that protein, carbohydrate, and lipid digestion is associated to specific regions of this organ. Moreover, a significant lysozyme activity in the lumen of the anterior and middle regions of the midgut was detected. This enzyme, together with the strong acidic luminal pH of middle tract, may play an important role in killing pathogenic microorganisms ingested with the feeding substrate. The evidence collected led us to propose a detailed functional model of the larval midgut of H. illucens in which each region is characterized by peculiar features to accomplish specific functions. This platform of knowledge sets the stage for developing rearing protocols to optimize the bioconversion ability of this insect and its biotechnological applications.

黑水虻（Hermetia illucens）幼虫是将有机废弃物等低品质生物质生物转化为可持续且富含营养的蛋白质以生产动物饲料的最具潜力的生物物种之一。尽管学界对该昆虫关注度颇高，但现有文献仅局限于黑水虻幼虫饲养方法的优化研究，尤其聚焦于其转化不同类型废弃物的效率，以及作为饲料原料的营养组成。令人意外的是，黑水虻的生物学特性却长期被忽视，而决定该昆虫卓越饮食可塑性的关键器官——幼虫中肠的形态与功能特性，至今仍未得到深入解析。本研究旨在填补这一知识空白。研究结果表明，幼虫中肠由多个解剖区域构成，各区域具有不同的管腔pH值与独特的形态功能特征。中肠上皮由多种细胞类型组成，分别参与营养物质的消化与吸收、中部区域管腔的酸化、内分泌调控以及上皮增殖。对参与营养消化的酶活性及其mRNA表达水平的详细表征显示，蛋白质、碳水化合物与脂质的消化与该器官的特定区域密切相关。此外，研究团队在中肠前部和中部区域的管腔中检测到了显著的溶菌酶活性。该酶与中部区域较强的酸性管腔环境协同，可能在杀灭随摄食底物进入体内的病原微生物方面发挥重要作用。基于收集到的全部证据，我们提出了黑水虻幼虫中肠的详细功能模型，其中每个区域均具备独特特征以实现特定功能。这一知识体系为优化该昆虫的生物转化能力及其生物技术应用的饲养方案开发奠定了坚实基础。