Abstract

Histology has long served as a valuable qualitative tool in the field of marine aquaculture, used to assess the microanatomy and cellular status of tissues and organs, as well as to investigate the presence of pathogens. This detailed understanding has enabled the evaluation of treatment effectiveness, monitoring of overall organism health and development, assessment of physiological condition, and the early detection of diseases. Despite these advantages, qualitative analysis alone lacks statistical validation, making image interpretation a challenging task. To address this limitation, digital quantitative histology has emerged in recent years. This technique involves digitizing histological slide images to quantify colored pixels associated with specific molecules or metabolites, depending on the staining method used. Additionally, these digital images enable the measurement of cellular and tissue structures. Various indexes applied to marine organisms, including fish, crustaceans, and molluscs have proven effective for assessing parameters such as the reproductive cycle, gonad quality, general condition, tissue and cell structure and morphology, oxidative damage, and characterization and detection of pathogens. These indexes provide valuable insights into the development and function of tissues and organs in situ. They provide a reliable means of evaluating and predicting the organisms condition and health status, which may not be readily apparent through biochemical or molecular biomarkers. This review presents a comprehensive compilation of indexes that utilize quantitative digital histological analysis, thereby contributing to our understanding of the health and physiological status of commercially important marine aquaculture species.