Basic entomology and Biodiveristy practicals.
Study of different types of hematocytes in cockroach & haemocyte count. Introduction
The blood or hemolymph of insects is contained in the general body cavity, where it baths the various internal organs and also enters the appendages and the tubular cavity of the wing-veins. It consist of the liquid plasma and numerous blood cells or heamocytes. Principle function of heamocytes is phagocytosis, i.e ingetion of small solid particales. In generalized insect there are basic six types of which first three occurs in all insects are as follows
a) Proheamocytes are rounded or oval cells 6-13 um n diameter with relatively large nucleus nad a few lare cytoplasmic granules.
b) The plasmocytes are rather larger, variable , round, oval, spindle shaped or amoeboid cells whose nuclei occupy about 40 percent of the cell volume and which have more or less finely granular or vacuolated cytoplasm.
c) The granular cells are round or oval, 10 -17 um in diameter and with nuclei which occupy about half the cell volume; their cytoplasm is packed with granules and can form the extensions which attaché the cells to their substrate.
d) Large spherule cells are oval or spindle shaped, 8-10 um in diameter and usually full of large granules or spherules 1.5 – 2 um across. Like the granular cells they exclude fine attachment processes
e) Cystocytes are round, 9-14 um in diameter, with a relatively large nucleus; in undiluted blood the plasma membrane of the Cystocytes becomes ill defined in vitro and the cell swells and gives rise to granular material associated with the clotting of the blood.
f) The Oenocytoids are relatively large cells up to 19 um in diameter with a relatively smaller nucleus and few cytoplasmic granules; they are most often seen in lepidoptera and can be confused with large spherule cells.
Procedure:
Individual cockroaches (adult male and female) were anesthetized by placing them in the chloroform jar. The partially anaesthetized cockroach was removed, the abdomen was palpated to facilitate circulation and the insect was bled by severing an antenna at first segment.
The drop of Haemolymph was spread on the slide, added a drop of diluted Giemsa stain and placed cover slip, waited for 30 min at room temperature to allow haemocytes to spread and adhere to the slides.
Slide was observed under low power then high power of microscope. Following different types of haemocytes were found.
Cockroach saline : 157 mM NaCl; 3 mM KOH; 2 mM CaCl2; 2 mM MgCl2; 5 mM trehalose; 8.6 mM HEPES buffer, pH 7.2
Observations
Among the six basic morphotypes of haemocytes, following four were observed in P. americana:
| prohaemocytes, |  |
| plasmatocytes, |   |
| granulocytes, |  |
| oenocytoids. |  This cell type was granular but more elongated than typical granular cells and showed distinctive filipodia after 30 min adhesion. This cell may represent the oenocytoid. |
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