Mechanisms of karyotype evolution in the Brazilian scorpions of the subfamily Centruroidinae (Buthidae)

Abstract

The recently-revised subfamily Centruroidinae is part of the New World clade of buthid scorpions. In this study, we analyzed the cytogenetic characteristics of nine of the 10 Brazilian centruroidines, and one undescribed species of the genus Ischnotelson, using a phylogenetic approach to determine the chromosomal rearrangements responsible for the differentiation of karyotypes among the species. The cytogenetic data recorded in the present study supported the new taxonomic arrangement of the Centruroidinae, with all the species of the same genus sharing the same or similar diploid numbers, i.e., 2n = 20 or 22 in Troglorhopalurus lacrau and T. translucidus, 2n = 25 or 26 in Ischnotelson sp., I. guanambiensis and I. peruassu, and 2n = 28 in Jaguajir agamemnon, J. pintoi and J. rochae. The karyotype modelling in the ChromEvol software indicated 2n = 18 as the ancestral diploid number of the Centruroidinae. The differentiation of karyotypes among the centruroidine genera was based on increasing chromosome numbers resulting from progressive fission events. These changes probably occurred prior to the diversification of the genera Ischnotelson, Jaguajir, Physoctonus and Rhopalurus, and appear to have played a more important role in karyotype evolution at the intergeneric level than the interspecific one. However, the observed increase in diploid numbers was not accompanied by changes in the number or location of ribosomal genes or telomeric sequences. The identification of meiotic cells in female specimens also allowed us to discuss the mechanisms of achiasmatic meiosis in scorpions.

Scorpions of the Horn of Africa (Arachnida: Scorpiones). Part XXI. Parabuthus (Buthidae) (Part II), with description of five new species from Somaliland and Ethiopia

“…This effect was observed frequently in different buthid species (e.g. Mattos et al, 2013;Šťáhlavský et al, 2014;Sadílek et al, 2015;Ubinski et al, 2018) and represents probably one of the typical cytogenetic characteristics in this scorpion family. Pocock, 1901 (Figures 1-4, 274-277, 305, Table 5) Parabuthus abyssinicus Pocock, 1901: 1;Kovařík et al, 2016: 12-19, figs.…”

Insights into the Karyotype Evolution of Charinidae, the Early-Diverging Clade of Whip Spiders (Arachnida: Amblypygi)

“…According to our data, DNA molecules of charinids are terminated by the so-called insect telomeric sequence (TTAGG) n , which is ancestral for arthropods [17]. This motif has been identified in many arachnid orders [17,35,45,78,79,89,91], including a whip spider of the family Phrynichidae, Damon medius [17]. While the same telomeric motif is usually shared by taxa on higher taxonomic levels, exceptions do occur [92][93][94][95], including arachnids [17].…”

“…The major rDNA cluster (45S rDNA) is by far the most utilized molecular chromosomal marker across diverse eukaryotic organisms, and especially in non-model groups [72][73][74]. The major rDNA cluster visualized either by 18S or 28S rDNA probes has already been localized in some spiders [36,46,73,[75][76][77], scorpions [45,76,[78][79][80][81][82], pseudoscorpions [83], harvestmen [84][85][86][87], ticks [73,88,89], and an amblypygid [18]. Mapping of this cluster often revealed a single NOR site, which is probably an ancestral pattern in arachnids [36].…”

Chromosome diversity in Buthidae and Chactidae scorpions from Brazilian fauna: Diploid number and distribution of repetitive DNA sequences

“…In the Brazilian scorpion fauna, cytogenetic studies are also neglected, with chromosomal data for only 27 species. In contrast to this scenario, scorpions have many cytogenetic particularities, such as the occurrence of monocentric and holocentric chromosomes, high intraspecific and interspecific variability of diploid number, and meiosis with achiasmatic behavior of the chromosomes and presence of multivalent chromosomal chains ( Mattos et al, 2018 ; Ubinski et al, 2018 ; Adilardi et al, 2020 ; Šťáhlavský et al, 2020 , 2021 ; Schneider et al , 2023). The knowledge of all these characteristics can help to hypothesize about the evolution of chromosomes with localized and diffuse-kinetochore, the relationship between the chromosome structure/organization and the putative chromosomal rearrangements, and the mechanism responsible for the genetic variability in scorpions.…”