Complex meiotic configuration of the holocentric chromosomes: the intriguing case of the scorpion Tityus bahiensis

Autor(es)

Schneider, Marielle Cristina ^[1] ; Zacaro, Adilson Ariza ^[2] ; Pinto-da-Rocha, Ricardo ^[3] ; Candido, Denise Maria ^[4] ; Cella, Doralice Maria ^[5]

Afiliação do(s) autor(es)

^[1] Univ Fed Sao Paulo, Dept Ciencias Biol, BR-09972270 Sao Paulo - Brazil

^[2] Univ Fed Vicosa, Dept Biol Geral, Vicosa, MG - Brazil

^[3] Univ Sao Paulo, Dept Zool, Sao Paulo - Brazil

^[4] Inst Butantan, Lab Artropodes, Sao Paulo - Brazil

^[5] Univ Estadual Paulista, Dept Biol, BR-13506900 Sao Paulo - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Chromosome Research; v. 17, n. 7, p. 883-898, OCT 2009.
• Citações Web of Science: 26

Resumo

Mitotic and meiotic chromosomes of Tityus bahiensis were investigated using light (LM) and transmission electron microscopy (TEM) to determine the chromosomal characteristics and disclose the mechanisms responsible for intraspecific variability in chromosome number and for the presence of complex chromosome association during meiosis. This species is endemic to Brazilian fauna and belongs to the family Buthidae, which is considered phylogenetically basal within the order Scorpiones. In the sample examined, four sympatric and distinct diploid numbers were observed: 2n = 5, 2n = 6, 2n = 9, and 2 = 10. The origin of this remarkable chromosome variability was attributed to chromosome fissions and/or fusions, considering that the decrease in chromosome number was concomitant with the increase in chromosome size and vice versa. The LM and TEM analyses showed the presence of chromosomes without localised centromere, the lack of chiasmata and recombination nodules in male meiosis, and two nucleolar organiser regions carrier chromosomes. Furthermore, male prophase I cells revealed multivalent chromosome associations and/or unsynapsed or distinctly associated chromosome regions (gaps, less-condensed chromatin, or loop-like structure) that were continuous with synapsed chromosome segments. All these data permitted us to suggest that the chromosomal rearrangements of T. bahiensis occurred in a heterozygous state. A combination of various factors, such as correct disjunction and balanced segregation of the chromosomes involved in complex meiotic pairing, system of achiasmate meiosis, holocentric nature of the chromosomes, population structure, and species dispersion patterns, could have contributed to the high level of chromosome rearrangements present in T. bahiensis. (AU)

• Processo FAPESP: 06/53275-3 - Diferenciação evolutiva entre os cromossomos holocêntricos e monocêntricos em algumas espécies de escorpiões da fauna brasileira, detectada pela análise ultraestrutural do complexo sinaptonêmico e regiões associadas, heterocromatina constitutiva e região organizadora de nucléolo
• Beneficiário: Marielle Cristina Schneider
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado