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

Abstract

ABSTRACT. We analyzed mitotic and meiotic cells of a Brazilian amblypygid, Heterophrynus longicornis, using conventional and molecular cytogenetic techniques (Giemsa staining, C-banding, Ag-NOR, and FISH with rDNA probe). This is the first study that focuses solely on amblypygid chromosomes; it was undertaken to add data on cytogenetic knowledge of this group and contribute to the understanding of chromosome evolution in the Arachnida. We found 2n = 66 for male and female individuals, monocentric chromosomes, and absence of morphologically differentiated sex chromosomes. C-banding showed heterochromatin in the pericentromeric region of most chromosomes. Mitotic and meiotic nuclei submitted to Chromosomal characteristics of a Brazilian whip spider silver impregnation and FISH revealed, respectively, Ag-NORs and ribosomal genes in the terminal region of two chromosome pairs. Most chromosome features that we observed in H. longicornis are shared with species of other arachnid orders; however, the absence of morphologically differentiated sex chromosomes in amblypygid contrasts with the remarkable variety of sex chromosome systems recorded for the Araneae. Consequently, we conclude that analysis of species of the Tetrapulmonata clade is useful for understanding the trends of sex chromosome evolution in this arachnid group.

Molecular technique reveals high variability of 18S rDNA distribution in harvestmen (Opiliones, Phalangiidae) from South Africa

“…Rhampsinitus has a terminal position of 18S rDNA clusters, similarly to basal harvestmen of the suborder Cyphophthalmi (Svojanovská et al 2016), and other arachnid groups such as spiders (e.g. Král et al 2013), amblypygids (Paula-Neto et al 2013), and South American scorpions (e.g. Mattos et al 2014).…”

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

“…We may only suppose (bearing in mind also the supportive results from other methods, see below) that chromosomal fusions leading to the reduction in high ancestral 2n represent one of the main mechanisms of karyotype differentiation in Charinidae. This notion is corroborated by the comparably high 2n in two derived amblypygid lineages, specifically in Damon medius (2n = 70; Phrynichidae) [17] and three species belonging to Phrynidae (Heterophrynus longicornis, 2n = 66; Paraphrynus robustus, 2n = 64; Phrynus marginemaculatus, 2n = 68) [7,18]. The high ancestral 2n of amblypygids may also be consistent with the recently proposed theory regarding the whole genome duplication in the common ancestor of scorpions and tetrapulmonate arachnids [39][40][41].…”

“…The cytogenetic features of amblypygids are highly underexplored. Apart from an early report on the charinid S. sarawakensis [16], they are confined to two derived families, Phrynidae and Phrynichidae [7,17,18]. With nine newly analyzed species, the present study increased the number of cytogenetically analyzed amblypygids to 18.…”

“…The 2n and telomere sequence mapping was reported for Damon medius (Phrynichidae) by Vítková et al [17]. Later, Paula-Neto et al [18] shed light on the karyotype of Heterophrynus longicornis (Phrynidae), including the distribution of heterochromatin and the number and position of nucleolar organizer regions (NORs). Recently, the karyotype data of one Phrynus and six Paraphrynus species (Phrynidae) were reported by Seiter et al [7], who evidenced a wide range of 2n (from 24 to 68).…”

Karyotype Evolution in Harvestmen of the Suborder Cyphophthalmi (Opiliones)

“…Clusters of rDNA have been mapped only in ∼ 30 species of spiders [Král et al, , 2011Král, 2007;Oliveira et al, 2007;Rodríguez-Gil et al, 2007;Araujo et al, 2008;Stávale et al, 2010Stávale et al, , 2011Dolejš et al, 2011], 17 species of scorpions [Schneider et al, 2009a, b;Schneider and Cella, 2010;Mattos et al, 2013], 1 species of Amblypygi [Paula-Neto et al, 2013], and 1 species of Palpigradi [Král et al, 2008]. However, in these studies, NORs were mostly visualized by silver staining, and FISH detection using specific probes for rDNA clusters has only been done in a few recent studies Forman et al, 2013;Paula-Neto et al, 2013;Adilardi et al, 2014Adilardi et al, , 2015Mattos et al, 2014;Sadílek et al, 2015]. It seems to be clear that the majority of arachnids possess 1 pair of rDNA loci mostly in a terminal position.…”