Cell composition of blood for Salvelinus malma (Salmonidae) from the Raduga River (Kamchatka)

Abstract

Hematopoiesis is a mechanism of multifunctional adaptation in vertebrates, including fish. Adaptive capabilities of populations are studied for a species of genus Salvelinus with high ecological plasticity. Char Salvelinus malma is represented in Kamchatka by the anadromous, river, brook, and several lake forms. Peripheral blood cells are investigated for this species juveniles and adults from the Raduga River in the lower Kamchatka River basin. The fish sampled in August 2013 were divided into two groups: sexually mature individuals (10 specimens) and juveniles (10 specimens). The body length (AC) of mature chars (mean ± standard deviation, range in brackets) was 338.90 ± 12.64 (304.0–380.0) mm, the body weight — 437.40 ± 57.74 (235.0–735.0) g, their sex ratio was close to 1 : 1. The length of juvenile chars was 150.50 ± 9.14 (104.0–195.0) mm, the weight — 33.90 ± 6.19 (10.1–68.8) g. Blood was sampled from the caudal vessel of alive fish immediately after catching, the blood smears were dried and fixed with May-Grunwald dye and then stained with azure-eosin. Composition of leukocytes and erythrocytes was determined on the stained blood smears. The blood cells were classified according to Ivanova (1983) and Zhiteneva et al. (1989). Statistical significance of the blood cells composition differences between fish groups was assessed using the Mann-Whitney U-test, after checking for normal distribution of characteristics (Kolmogorov-Smirnov test). The erythroid row of S. malma was represented by proliferating (erythroblasts, basophilic and polychromatophilic normoblasts), maturing (oxyphilic normoblasts) and mature erythrocytes, the leukocyte row — by blast cells, agranulocytes and granulocytes. The juveniles were characterized by intense proliferative processes (great number of immature erythrocytes, large and medium lymphocytes, presence of blast cells) and appearance of poikilocytes; the sexually mature chars were distinguished by greater number of granulocytes, mainly due to stab and segmented neutrophils (p < 0.01). Parasitological analysis showed different infestation of the juvenile and adult chars by pathogenic helminths (Anisakis simplex, Eubothrium salvelini, Neoechinorhynchus salmonis) that influenced on their blood. Broad adaptive capabilities of S. malma hematopoiesis provided by wide morphological and functional diversity of blood cells are concluded that maintains homeostasis of the species. Blood indices for char from the Raduga River can be used to form reference intervals for monitoring physiological state of this species.