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

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).Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Programa de Pesquisas em Biodiversidade do Semiarido-PPBio SemiaridoUniv Estadual Paulista UNESP, Dept Biol, Inst Biociencias, BR-13506900 São Paulo, BrazilUniv Fed Piaui UFPI, BR-64800000 Floriano, Piaui, BrazilInst Butantan, Lab Especial Colecoes Zool, BR-05503900 São Paulo, BrazilUniversidade Federal de São Paulo UNIFESP, Dept Ciencias Biol, BR-09972270 São Paulo, BrazilUniversidade Federal de São Paulo UNIFESP, Dept Ciencias Biol, BR-09972270 São Paulo, BrazilFAPESP: 2010/14226-2FAPESP: 2011/21643-1CNPq: 478630/2010-7Programa de Pesquisas em Biodiversidade do Semiarido-PPBio Semiarido: CNPq 558317/2009-0Web of Scienc