Acanthocrios furnarii (Cordero & Vogelsang, 1928)

Poggio, Maria G., Bressa, Maria J., Papeschi, Alba G., Iorio, Osvaldo Di & Turienzo, Paola, 2009, Insects found in birds’ nests from Argentina: cytogenetic studies in Cimicidae (Hemiptera) and its taxonomical and phylogenetic implications, Zootaxa 2315 (1), pp. 39-46 : 41

Acanthocrios furnarii

As is characteristic of Hemiptera , chromosomes are holokinetic, i.e. without a localized centromere. In all A. furnarii population samples, the diploid chromosome number of males and females is 2n = 12 (10 + XY/XX). In oogonial prometaphases, two chromosomes are much smaller than the others, and correspond to the smallest autosomal pair ( Fig. 1a ); in spermatogonial prometaphases three smaller chromosomes are detected: two corresponding to the smallest autosomal pair and the other one to the Y chromosome ( Fig. 1b ).

During male meiosis chromosomes condense from leptotene to pachytene, but no diplotene or diakinesis stages are observed, i.e., meiosis is achiasmatic. At metaphase I, the five autosomal bivalents are completely condensed; homologues are connected with each other through the medial region, but the telomeric regions are separated ( Fig. 1c ). At this stage both the autosomal bivalents and the sex univalents dispose at the equatorial plate with their long axes perpendicular to the spindle pole. At anaphase I, the sex chromosomes X and Y segregate sister chromatids (equational division) whereas autosomal bivalents segregate homologous chromosomes (reductional division). Both the sex chromatids and the homologous autosomes migrate parallel to the equatorial plane. At metaphase II, the sex chromatids associate forming an XY pseudobivalent, which lies at the centre of the ring formed by the autosomes ( Fig. 1d ). At anaphase II, the autosomes segregate equationally and the X and Y chromatids divide reductionally. At this stage the chromosomes segregate also with their long axes parallel to the equator. Telophase II nuclei have 6 chromosomes (5A + X or 5A + Y).

Figures

FIGURE 1. Mitotic and meiotic chromosomes of Acanthocrios furnarii: a, oogonial prometaphase; b, spermatogonial prometaphase; c, metaphase I; d, metaphase II. Arrows: sex chromosomes. Arrowheads: smallest autosomal pair. Chromosomes are stained with 2 % iron acetic haematoxylin. Bar = 10 µm.