Comparison of hemocytes of 5th-instar nymphs of Rhodnius prolixus (Stal) and Rhodnius robustus (Larousse 1927), before and after molting

Abstract

The immune response of insects involve humoral factors and celular elements named as hemocytes. There are different reports exploting the response of hemocytes against infections but the molting effect on this response has not been explored so far. The aim of this work was to compare the hemogram: the formula and the differential counting of hemocytes in 4th and 5th instar nymphs of Rhodnius prolixus and Rhodnius robustus, 24 hours after molting. We assayed different staining methodologies including Giemsa, Alcian Blue pH 2.0, Alcian Blue pH 2.6, Gomori substrate, PAS (Schiff), Sudan Black and Papanicolau with positive controls for each one. On the Gomori staining, we observed lysosomes in the granulocytes and plasmatocytes but the differentiation was better detected using Giemsa staining. The plasmatocytes were abundant across the 4th instar nymphs of R. robustus and 5th instar nymphs of R. prolixus. The cell counting of prohemocytes was higher, the oenocitoids, spherulocytes and adipohemocytes did not reach 1%. In the two species studied, there were no statistically significant differences across plasmatocytes (p=0,05319), not even in granulocytes (p=0,5) but significant in the prohemocytes (p=0,001).

Keywords

• Rhodnius prolixus
• Rhodnius robustus
• hemocytes
• molt