Spermatogenesis in Tenebrio molitor (Tenebrionidae, Coleoptera): A Fine Structure and Anti‐tubulin Immunofluorescence Study

Abstract

Wolf; K. W. & Hellwage. J. 1995. Spermatogenesis in Tenebrio moliror (Tenebrionidae. Coleoptera): A fine structure and anti-tubulin immunofluorescence study.-Acia Zoologica (Stockholm) 76: 267-279.Spermatogonia and both generations of spermatocytes of Tenebrio mofiior possess conventional bipolar spindles with only few aster MTs. Spindles in metaphase spermatogonia are surrounded by fenestrated two-layered cisternae and do not contain intraspindle membranes. In metaphase sperrnatocytes, a spindle envelope is missing, but inuaspindle membranes are abundant. Mitochondria form long threads lateral to the nucleus in prophase I of meiosis. The elongated mitochondria also align parallel to the spindle apparatus in prometaphase I. As a consequence, the spindles reside in a cage formed of mitochondria. This arrangement may guarantee proper bisection of the chondriorne during division. Cells are tightly packed during spermatogonial divisions and in prophase I, but large intercellular spaces develop when the first meiotic spindle assembles. Then, cytoplasmic bridges which persist between the cells as a result of incomplete cytokinesis appear as slender tubes. Anti-tubulin immunofluorescence using an antibody against acetylated a-tubulin revealed intense acetylation throughout spermatogonial mitosis but a low degree of a-tubulin acetylation in meiotic spindles prior to telophase. This may indicate a high microtubule turnover in meiosis.

Fine structure of the kinetochores in six species of the Coleoptera

“…In both species, the metaphase spindle of primary spermatocytes was located in a basket formed of elongated mitochondria. However, the two species also showed clear-cut differences in that A. alni possessed a membranous bilayered spindle envelope, while the spindle-associated membranes of T. molitor formed small irregular elements scattered throughout the spindle matrix (Wolf and Hellwage 1995;Wolf and Joshi 1995;Wolf 1996~). Thus, traits of the spindle apparatus could also play a role during karyotype evolution in that, for example, a membranous spindle envelope renders loss of chromosomes during division less likely.…”

“…A total of 6 species from 5 different families were studied. The darkling beetle T. molitor, a model organism in the Coleoptera that has been repeatedly studied (e.g., Cameron 1965;Baccetti et al 1973;Wolf and Hellwage 1995;Wolf and Joshi 1995), was used to determine whether kinetochore structure varies depending on the cell type. This appeared necessary, because in another insect order, the Hemiptera, kinetochore plates were missing in primary spermatocytes, while the chromosomes in spermatogonial divisions possessed trilaminar kinetochores (Wolf 1996a;Buck 1967;Comings and Okada 1972;Ruthmann and Permantier 1973).…”

“…Animals of a wild-type laboratory strain of T. molitor, reared on rolled oats, were used in the present study (compare Wolf and Hellwage 1995;Wolf and Joshi 1995). Adults of A. murina, A. villosoviridescens, C. septempunctata, and C. graminis were collected in the field at a location 1-1.5 km west of Gross Wesenberg (Schleswig Holstein, Germany), transferred to the laboratory, and prepared for electron microscopy the next day.…”

The structure of the Xyp sex chromosome complex in male meiosis of two beetles: Tenebrio molitor (Tenebrionidae) and Chrysolina graminis (Chrysomelidae)

“…For information on spindle structure and assembly and the processes of meiosis and spermiogenesis in this beetle the reader is referred to previous articles of the author. It should be added that the first meiotic spindles show a conventional bipolar design [10,11]. The analysis of a serially sectioned metaphase I chromosome plate revealed that the autosomal bivalents were cylinders oriented with their long axes parallel to Research Articles Figure 7.…”

“…Animals of a wild-type laboratory strain of T. molitor were reared on rolled oats [cf. 10,11]. Adults of C. graminis were collected in the field about 1 km west of Groß Wesenberg (Schleswig Holstein, Germany) in May of 1994, transferred to the laboratory, and prepared for electron microscopy the next day (see below).…”