In the current study, the histological structure of the gallbladder of Alburnus tarichi (Güldenstädt, 1814) was investigated. Hematoxylin and eosin were used to stain the histological sections for routine examinations, in addition to using periodic acid Schiff (PAS) for the neutral mucins, aldehyde fuchsin (AF) for the sulphated mucins, and Alcian blue (AB; pH: 2.5) for the acidic mucins. In addition, proliferating cell nuclear antigen (PCNA) immune-staining was performed for the detection of dividing cells among the epithelium. The gallbladder of A. tarichi was composed of mucosa, muscularis, and serosa or adventitia layers. The mucosa covering the wavy pleomorphic folds was made up of tall columnar epithelium and a lamina propria. The apical surface of the epithelial cells was lined by continuous short microvilli. On the epithelium, the luminal surface was remarkably stained with PAS, AF, and AB. Slight to moderate staining was observed on the epithelial cells in the apical zone with PAS. The cytoplasm of epithelial cells were stained in a slight manner with AF. No goblet cells were observed among the epithelium. According to the PCNA immune-staining, some epithelial cells were observed to proliferate. The lamina propria consisted of loose connective tissue that contained fibrocytes, collagen and elastic fibers, capillaries, and small blood vessels. The muscularis layer displayed muscle fibers that were circular, smooth, and surrounded by collagen fibers. The subserosal and serosal or adventitial layers had typical morphology to those of other fish and vertebrates.
KEY WORDS: Gallbladder; Alburnus tarichi; Fish; Histology; Histochemistry; PCNA.