THE HEMOCYTES OF RHODNIUS PROLIXUS STÅL

¹ Department of Entomology, University of Maryland, College Park, Maryland

1. The hemocytes of Rhodnius prolixus have been studied with phase contrast microscopy, after supravital staining, and in fixed and stained smears.

2. With phase contrast microscopy, the following categories of circulating cells can be readily identified: (a) non-dividing and mitotically-dividing prohemocytes, (b) non-vacuolated and vacuolated plasmatocytes, (c) intact and quickly lysing granular hemocytes, (d) oenocytoids with and without special cytoplasmic inclusions, (e) adipohemocytes, and fat body cells, and (f) granulocytophagous cells.

3. This classification and terminology are compared with those of Wigglesworth. It is suggested that the cell which Wigglesworth terms an oenocytoid is more comparable to the granulated blood cells of other insects and may be referred to as a granular hemocyte. It is suggested that the cells which Wigglesworth refers to as large non-granular spindle cells and non-phagocytic giant hemocytes are comparable to the oenocytoids of other insects.

4. Vacuolation of plasmatocytes can be prevented by heat-fixing for Rhodnius. Lysis of granulocytes can be prevented by collecting hemolymph into 0.75% Versene.

5. Attempts to correlate an increase in sizes of circulating plasmatocytes with secretion of the thoracic gland hormone in fourth and fifth stage nymphs were not successful because of the great variability in the sizes of these cells.

6. Since most circulating plasmatocytes in differential hemocyte counts of unfixed fourth stage nymphs were identified as the vacuolated type, no correlation was possible between their vacuolation and the secretion of the thoracic gland hormone.

7. In unfed fifth stage nymphs, most of the circulating plasmatocytes were classified as vacuolated cells. Between the first and second days after the nymphs took a blood meal, the percentages of plasmatocytes identified as vacuolated cells abruptly decreased and steadily declined during the rest of the stadium.