On Counting Mitotically Dividing Cells in the Blood of the Cockroach,Periplaneta orientalis (Linn.) ∗

Abstract

Although cell divisions in insect blood have been described by Hollande 1 and others, few quantitative counts apparently have been reported. This is a preliminary report of blood cell counts in P. orientalis, especially mitotically dividing cell (M.D.C.) counts. Large nymphs were used.

Method. Antennal blood is taken into a pipette, made to handle 1.22 mm.³ blood, and rapidly diluted; a total count is obtained with a hemocytometer. A small drop of the antennal blood is placed also in a larger drop of diluting fluid on a slide, immediately stirred to prevent cell coagulation, covered with a coverslip, and rimmed with oil to prevent evaporation. The cells are randomly counted (oil immersion) and the % M.D.C. determined. The diluting fluid consists of 0.081 M NaCl, 0.002 M KCl, 0.001 M CaCl₂, 0.005% Gentian Violet, 0.125% glacial acetic acid.

Results. Some of the counts obtained are in Table I. Groups I and II include normal animals. In Group I only anaphases and telophases, while in Group II prophases, metaphases, anaphases, and telophases were counted. Each animal was bled only once, to make the count. Group III contains 3 series of 3 animals each: 1 control, bled once for the count, and 2 experimental animals bled extensively at previous times; for example, No. A-2 was bled at 4 and again at 2 days before the count. Group IV includes 1 control, bled once for each count, and 1 experimental animal, also bled extensively after each count. This experiment lasted 14 days.

Discussion and Conclusions. The average total cell count of Groups I and II is 31,672 cells/mm.³ blood, or about the same as the count for P. fuliginosa obtained previously. 2 The average. % M.D.C. is 0.07 in Group I and 0.51 in Group II. Assuming this, difference to be due (1) to the counting of all phases in Group II and only anaphases and telophases in Group I and (2) to a longer time duration of pro- plus meta- as compared to ana- plus telophase, then the observed difference would indicate that the average mitotically dividing cell remains in all mitotic phases about 7 times as long as in the last 2 phases.