Ultrastructure of haemocytes of tropical tasar silkworm Antheraea mylitta Deury

Tasar silkworm, Antheraea mylitta Drury is commercially exploited in tropical India and exposed to varied climatic conditions. Basic information on the ultrastructure of the haemocytes indicated that these are five types of haemocytes, namely, prohaemocytes (PRs), oenocytoids (OEs), plasmatocytes (PLs), spherulocytes (SPs) and granulocytes (GRs). PRs were usually round in shape and relatively smaller than other haemocyte types and were characterised by light purple staining of cytoplasm with Giemsa stain and a low concentration of granules in their cytoplasm. PRs measured 8.500 to 18.063 μm (mean 11.794±1.138 μm) in diameter and their nuclei, which were deeply stained in deep purple colour in Giemsa stain, were relatively large in comparison with other types. OEs cells were characterised by their spherical or ellipsoidal shape, large amount of cytoplasm and small nuclei. Their mean length of larger axis was 21.548±1.322 μm (ranged between 14.875 to 25.500 μm) and smaller axis was 19.975±1.344 (ranged between 14.875 to 25.500 μm). Their cytoplasm stained little yellowish red in Giemsa stain. PLs were round to elliptical in shape. Several fusiform PLs were also observed. The longer axis of elliptical forms ranged from 12.750 to 23.375 μm (mean 18.913±1.130 μm) and in fusiform cells it varied in between 17.000 to 34.000 μm (mean 23.375±2.138 μm). SPs were round to oval in shape. The longer axis of SPs ranged from 12.750 to 29.75 μm (mean 20.740±1.610 μm) and smaller axis ranged from 4.250 to 12.750 μm (mean 9.350±1.117 μm). The cell area and volume of regular-shaped haemocytes were also observed. The shape of the nucleus was irregular. GRs were recognised as spherical or oval shaped haemocytes, which varied considerably in size The long axis of GRs ranged in between 12.750 to 25.500 μm (mean 19.975±1.344 μm). The shorter axis ranged between 8.500 to 23.375 μm (mean 15.088±1.473 μm). The cytoplasm had numerous vacuolar bodies distributed around the nucleus. The nucleus stained deep purple and was irregular in shape. Densely dispersed cytoplasmic inclusions clearly distinguish GRs from other types. Surface characteristics of haemocytes under scanning electron microscope revealed smooth to highly irregular surface. Mitotic cells and degenerated cells were also seen.