TOTAL HEMOCYTE CONTENT AND HEMOCYTE COMPOSITION OF HEMOLYMPH OF AUTUMN AND SPRING GENERATION APIS MELLIFERA L.

Abstract

In many countries of the world, massive honey bee colony losses have been observed in recent decades. In temperate latitudes, Apis mellifera L. mortality increases during or after wintering. Wintering bees are bees of the autumn generation, which live the longest - up to 8 months. They have to raise the spring generation of bees. During wintering stress can arise in bees, which depends on many abiotic (low temperatures, quality of food) and biotic (parasites and pathogens) factors. At the same time, resistance to pathogens is determined by the state of immunity.Honey bees have innate immunity, which is provided by cellular and humoral mechanisms. Hemocytes participate in both cellular and humoral links of immunity. The aim of our study was to evaluate the quantitative and qualitative cellular composition of the hemolymph of adults of Apis mellifera L. of the autumn and spring generations. The experiment was conducted during the autumn-winter-spring period, on workers of honey bees of the autumn and spring generations, without signs of infectious diseases. Wintering took place in a room with a constant temperature in the range from 0 to +5 °С. The age of bees of the autumn generation was 20–25, 35–40, 50–55, 195–200, 205–210, 215–220, 235–240 days, and of the spring generation – 20–25. Hemolymph was collected from bees, the individual number of hemocytes in 1 μl of hemolymph was counted, swabs were made to calculate the hemocytic formula. Prohemocytes, plasmatocytes, granulocytes, permeable cells were identified on smears of the hemolymph of experimental bees (they were found in small numbers and not in all bees). The number of hemocytes in 1 μl of hemolymph of bees of the autumn generation of most age categories varies significantly and is in the range from 5×103 to 60×103 cells. In individuals aged 195–200, 215–220 days and bees of the spring generation, the number of hemocytes in 1 μl of hemolymph is within 5–15×103, the average values are 9303,8; 6986,1 and 9836,6 cells, respectively. Individual indicators of the total number of hemocytes of the studied bees are quite variable. In individuals of the autumn generation, with increasing age, the content of hemocytes undergoes wave-like fluctuations. Unidirectional changes in the direction of an increase or decrease in the content of cells in the hemolymph of experimental bees were not detected. In the hemograms of A. mellifera, both autumn and spring generations, oval plasmatocytes predominated. In the hemolymph of bees of the autumn generation, starting from the age of 205–210 days, the content of granulocytes with phagocytic activity increases, compared to younger individuals of the autumn generation and bees of the spring generation. This may be caused by an active aging process combined with contact with pathogens in nature, because individuals of this age began to fly out of the hive to collect pollen and nectar. Bees of the spring generation have the highest prohemocyte content, which indicates active hematopoiesis.