Sex-Specific Baseline Levels of Selected Immune Biomarkers in the Skin Mucus of Rainbow Trout (Oncorhynchus mykiss)

Abstract

Fish skin mucus plays a critical role in maintaining homeostasis through its various components while serving multiple functions, such as ionic regulation, osmotic balance, immune response, and disease resistance, making it a highly multifunctional material. Since mucus provides a non-invasive means of monitoring fish physiology, health, and welfare, it is important to provide baseline data on its components as biomarkers of immunity. This study assesses the baseline values of various biomarkers, including C-reactive protein (CRP), total protein, total immunoglobulins (Ig), myeloperoxidase (MPO), total antioxidant status (TAS), nitroblue tetrazolium (NBT) and lysozyme activity in rainbow trout (Oncorhynchus mykiss) epidermal mucus, with a focus on sex-based differences. The baseline values for CRP and TAS in the skin mucus of rainbow trout were established for the first time, providing a foundational reference point for mucosal immunity. We observed significant changes in total Ig, lysozyme activity and MPO, with varying responses between sexes. However, no overall differences were observed between females and males based on the other assessed parameters. This study provides baseline data for various innate immunity parameters in the skin mucus of rainbow trout under normal conditions, which can serve as a critical reference for understanding fish health and welfare.

Keywords

• Cutaneous mucus
• baseline values
• non-specific immunity
• rainbow trout

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