Objective: To compare different identifying methods of the mast cells of red crucian carp (Cyprinus carpio).
Methods: The gill filaments were taken from Cyprinus carpio infected with Edwardsiella tarda and fixed in Bouin's solution. The hematoxylin-eosin (HE), toluidine blue (TB), Alcian blue (AB), neutral red, Masson trichrome, May-Grunwald Giemsa (MGG) stainings and streptavidin-biotin complex (SABC) immunohistochemical method were used to observe the mast cells. The smears of head kidney stained by Wright-Giemsa were used as a supplementary method.
Results: AB and TB were desirable staining solutions for clearly displaying mast cells, and MGG staining came second. Immunohistochemical method showed the small number of tryptase-positive mast cells and a weak positive reaction. The cells in smears were dispersed and showed different developmental stages.
Conclusion: The immunohistochemistry and the histochemical staining combined with Wright-Giemsa-stained smears are two good ways to identify the mast cells of fish.