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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Agência Nacional de Águas

Instituto Federal de Mato Grosso

Labomar, Instituto de Ciências do Mar, Universidade Federal do Ceará

Universidad Nacional del Centro de la Provincia de Buenos Aires

Instituto Nacional de Pesquisas da Amazônia

Universidade de São Paulo

Scorpions represent an intriguing group of animals characterized by a high incidence of heterozygous chromosomal rearrangements. In this work, we examined six species of Tityus (Archaeotityus) from Brazilian fauna with a particular focus on elucidating the rearrangements responsible for the intraspecific variability of diploid number and the presence of long chromosomal chains in meiosis. To access any interpopulation diversity, we also studied individuals from four species representing distinct localities. Most species demonstrated intraspecific polymorphism in diploid number (2n = 19 and 2n = 20 in T. clathratus, T. mattogrossensis, and T. pusillus, 2n = 16, 2n = 17 and 2n = 18 in T. paraguayensis, and 2n = 16 and 2n = 24 in T. silvestris) and multi-chromosomal associations during meiosis I, which differed even among individuals with the same chromosome number. In some species, the heterozygous rearrangements were not fixed, resulting such as in Tityus clathatrus, in 11 different chromosomal configurations recognized within a same population. Based on meiotic chromosome behaviour, we suggested that independent rearrangements (fusion/ fission and reciprocal translocations), occurring in different combinations, originated the multi-chromosomal chains. To evaluate the effects of these chromosome chains on meiotic segregation, we applied the chi-square test in metaphase II cells. The non-significant occurrence of aneuploid nuclei indicated that non-disjunction was negligible in specimens bearing heterozygous rearrangements. Finally, based on our analysis of many chromosome characteristics, e.g., holocentricity, achiasmate meiosis, endopolyploidy, ability to segregate heterosynaptic or unsynapsed chromosomes, (TTAGG)n sequence located in terminal regions of rearranged chromosomes, we suggest that the maintenance of multi-chromosomal associations may be evolutionarily advantageous for these species.

Universidade Estadual Paulista “Júlio de Mesquita Filho” UNESP Departamento de Biologia

Universidade Federal do Piauí UFPI Campus Almícar Ferreira Sobral Floriano

Universidade Federal de Mato Grosso UFMT Departamento de Biologia e Zoologia

Universidade Federal de São Paulo UNIFESP Departamento de Ecologia e Biologia Evolutiva

Pós-Graduação em Zoologia Universidade Federal de Minas Gerais UFMG

Universidade Estadual Paulista “Júlio de Mesquita Filho” UNESP Departamento de Biologia

FAPESP: 2011/21643-1

FAPESP: 2013/11840-0

Agência Nacional de Águas: 23561–1

Labomar, Instituto de Ciências do Mar, Universidade Federal do Ceará: 25471–1

Labomar, Instituto de Ciências do Mar, Universidade Federal do Ceará: 40014–2

Universidad Nacional del Centro de la Provincia de Buenos Aires: 41383–2

Instituto Nacional de Pesquisas da Amazônia: 48224–1