High chromosome variability and the presence of multivalent associations in buthid scorpions

Abstract

In this study, we investigated the mitotic and meiotic chromosomes of 11 Buthidae scorpion species, belonging to three genera (Ananteris, Rhopalurus and Tityus), to obtain detailed knowledge regarding the mechanisms underlying the intraspecific and/or interspecific diversity of chromosome number and the origin of the complex chromosome associations observed during meiosis. The chromosomes of all species did not exhibit a localised centromere region and presented synaptic and achiasmatic behaviour during meiosis I. Spermatogonial and/or oogonial metaphase cells of these buthids showed diploid numbers range from 2n = 6 to 2n = 28. In most species, multivalent chromosome associations were observed in pachytene and postpachytene nuclei. Moreover, intraspecific variability associated with the presence or absence of chromosome chains and the number of chromosomes in the complex meiotic configurations was observed in some species of these three genera. Silver-impregnated cells revealed that the number and location of nucleolar organiser regions (NORs) remained unchanged despite extensive chromosome variation; notably, two NORs located on the terminal or subterminal chromosome regions were commonly observed for all species. C-banded and fluorochrome-stained cells showed that species with conspicuous blocks of heterochromatin exhibited the lowest rate of chromosomal rearrangement. Based on the investigation of mitotic and meiotic cells, we determined that the intraspecific variability occurred as a consequence of fission/fusion-type chromosomal rearrangements in Ananteris and Tityus species and reciprocal translocation in Rhopalurus species. Furthermore, we verified that individuals presenting the same diploid number differ in structural chromosome organisation, giving rise to intraspecific differences of chromosome association in meiotic cells (bivalent-like elements or chromosome chains).

Chromosomal characteristics of a Brazilian whip spider (Amblypygi) and evolutionary relationships with other arachnid orders

“…The number and location of NORs were only established, for example, in approximately 30 species of Araneae (Král et al, 2006;Král, 2007;Oliveira et al, 2007;Rodríguez-Gil et al, 2007;Araujo et al, 2008;Stávale et al, 2010Stávale et al, , 2011Dolejš et al, 2011;Král et al, 2011), 17 species of Scorpiones (Schneider et al, 2009a,b;Schneider and Cella, 2010), 3 species of Opiliones (Gorlov and Tsurusaki, 2000;Oliveira et al, 2006;Schneider et al, 2008;Mattos et al, 2013), and two species of Palpigradi (Král et al, 2008). In almost all these species, the NORs were only identified through the use of silver impregnation; however, in an overview of the NOR distribution in Coleoptera, Schneider et al (2007) showed that the results were usually coincident when the chromosomes were examined with both silver impregnation and FISH technique.…”

Organization and Behavior of the Synaptonemal Complex during Achiasmatic Meiosis of Four Buthid Scorpions

“…The specimens were dissected in saline solution (128.3 m M NaCl, 16.7 m M Na 2 HPO 4 , 19.9 m M KH 2 PO 4 ), and the testes were removed and divided into 2 parts. One part of each testis was used for light microscopy analyses [Mattos et al, 2013] and the other part was subjected to cellular microspreading to visualize the SCs and associated structures under transmission electron microscopy (TEM), according to Loidl and Jones [1986]. The microspread cells were silver-impregnated following Kodama et al [1980].…”

“…These rearrangements, when present in a heterozygous condition, result in multiple chromosomal associations during meiosis I, which can even involve all the chromosomes of the diploid set. As an additional peculiarity, all species of the family Buthidae have holocentric chromosomes [Shanahan, 1989a, b;Mattos et al, 2013;Schneider et al, 2014].…”

“…Koch, 1839), 2n = 28, which showed a complex chain involving all chromosomes of the complement; (2) Rhopalurus rochai Borelli, 1910, 2n = 28, which exhibited interindividual variation, i.e. 10 'bivalents' [for definition, see Mattos et al, 2013] plus 1 chain of 8 chromosomes, or 9 'bivalents' plus 1 chain of 10 chromosomes; (3) Tityus bahiensis (Perty, 1833), 2n = 6, which revealed 1 chain of 6 chromosomes, and (4) Tityus fasciolatus Pessôa, 1935, 2n = 14, which exhibited 7 bivalentlike elements [for definition, see Mattos et al, 2013].…”

Review of Northwestern African Buthacus, with description of Buthacus stockmanni sp. n. from Morocco and Western Sahara (Scorpiones, Buthidae)

“…Both characters are typical for the scorpions from the family Buthidae (e.g. Mattos et al, 2013). The chromosomes of the first pair are significantly longer (13.41 % of the diploid (50), and movable finger dentition (51).…”