POLAR CYTOPLASMIC EVAGINATIONS IN DIVIDING SPERMATOCYTES OF THE FIREBUG, PYRRHOCORIS-APTERUS (PYRRHOCORIDAE, HEMIPTERA)

The present fine structure and anti-tubulin immunofluorescence study d eals with evaginations from the cell surface in metaphase I spermatocy tes of the firebug Pyrrhocoris apterus (Pyrrhocoridae, hemiptera). The surface of spermatogonia and prophase spermatocytes was smooth throug hout. Only in metaphase I and anaphase I, cytoplasmic threads projecte d from polar portions of the spermatocytes. In contrast, equatorial po rtions of these cells possessed a smooth surface. By mid to late telop hase, the evaginations were no longer detectable in spermatocytes. Thr ee ideas are at hand to explain the development of polar cytoplasmic e vaginations. First, they could represent a membrane reserve used up du ring spindle elongation in telophase of meiosis. In order to test this idea, spindle structure was analyzed in meiosis I using simultaneousl y antibodies to beta-tubulin and gamma-tubulin, gamma-Tubulin represen ts a tubulin isoform prevalent in centrosomes. The observations showed that spindle elongation was not very prominent in meiosis of the bug. Although it cannot be ruled out, the formation of a polar membrane re serve prior to spindle elongation is not a likely explanation for the evaginations from the cell surface. Second, the development of surface extensions could bring about increased exchange of metabolites during a particulaly active stage of meiosis. Third; the polar evaginations could be an inadvertent product of the aster microtubules protruding t owards the plasma membrane.