Goldfish (Carassius auratus) gills function as both respiratory and immuneregulatory organs, integrating neuroendocrine and immune responses to environmental
stimuli. This study explores the spatial organization and interaction of neuroendocrine
cells (NECs) and immune cells within goldfish gills using confocal immunohistochemistry
and transmission electron microscopy. NECs, identified near blood capillaries and nerve
fibers, highlight their role in environmental sensing and physiological regulation. These
cells express serotonin (5-HT), a neurotransmitter critical for neuroimmune communication.
Two distinct macrophage subsets were observed: iNOS-positive macrophages, concentrated in the basal epithelium, suggest a pro-inflammatory role, whereas 5-HT-positive
macrophages, dispersed in the subepithelium, likely contribute to immune modulation. The
co-localization of MHC-II and CD68 in macrophages further supports an active antigenprocessing system in the gills. Ultrastructural analysis revealed diverse immune cells,
including rodlet cells, telocytes, and lymphocytes, within the gill epithelium. Telocytes
formed intricate networks with immune cells, highlighting their role in immune coordination and tissue homeostasis. These findings provide new insights into the neuroimmune
interactions in fish gills, contributing to a broader understanding of aquatic immune
systems and environmental adaptability.