Erythrocyte morphometry in pontic shad (Alosa immaculata).

Abstract

Pontic shad (Alosa immaculata) is a migratory fish species, which undergoes long migrations along the Danube River, from Black Sea to the first obstacle that stops the migration the Iron Gate II dam. Individuals used in this study were caught using drift nets, in 2018 (n=11) and 2019 (n=11), few kilometres down stream of the Iron Gate II Dam, near village of Prahovo, Serbia. Blood samples were taken from live individuals and two blood smears were prepared, on microscopic slides, for each individual. Slides were stained with Bio-Diff kit (Bio Optica, Milano, Italy) and observed and photographed under DM RB photomicroscope (Leica, Wetzlar, Germany). Pictures were analysed using the Digimizer image analysis software which automatically calculated celular and nuclear parameters of red blood cells. The proportion of immature, intermediate, and mature erythrocytes were calculated and the differences in cellular and nuclear parameters were tested using the Mann-Whitney U test. Average length of the fish caught at 2018 was 31.9±3.9 cm, with the average weight of 188.9±48.9 g. Individuals from 2019 sampling had an average length of 29.6±2.7 cm, and the average weight of 147.2±57.5 g. Average value of Fulton’s condition factor did not differ between sampling seasons (K=0.57). Overall, in both years, immature erythrocytes constitute the majority (>57%) of analysed red blood cells. Individuals caught at 2018 had higher proportion of immature and intermediate cells, while fish caught at 2019 had higher proportion of mature cells- Man-Whitney U test showed no statistically significant differences in cell area, parameter and length between fish caught at different years. The same morphometirc parameters, observed for nuceus, showed statistically significant differences. Our study shows that anadromous fish, such as pontic shad, which undergoes long migrations, have 2-2.5 times higher proportion of immature erytrocytes then potamodromous vimba bream (Vimba vimba), a medium distance migratory fish species.