LAUSR

Abstract This paper provides a review of literature published in 2000–2016 on the responses of lysozyme in cyprinids, which was experimentally obtained based on substances of different origin. Ten species, representing objects of aquaculture, are studied. The effects of pathogenic and parasitic infection, vaccination, and immunization, as well as immunostimulants, including endotoxins, secondary metabolites, components of plant origin, and hormones administered by injection, are considered. The pathogenic challenge of carp Cyprinus carpio L. by Aeromonas hydrophila (Chester) shows multidirectional changes and their absence in the activity of lysozyme. The parasitic infection of different fish species usually has an immunosuppressive effect. Vaccination and immunization increase serum lysozyme activity, which is 7–8 times higher than that in the control fish. However, the immune responses differ in time and depend on some factors, including the structure of the active substance and composition of the vaccine. Most immunostimulants contribute to different growths in the activity and content of lysozyme in carp serum and organs. Immune responses can reverse, depending on the dose of the active substance. The diversity of units of lysozyme activity makes it difficult to systematize immune responses even within a single fish species. The range of variation in the serum lysozyme activity of Cyprinus carpio and Labeo rohita (Hamilton) is very wide in studies conducted by different researchers, which probably cannot correspond to adequate physiological values. There are data indicating the highest mortality among experimental fish that have the highest serum lysozyme activity.