Chromosomal similarities between Nephilidae and Tetragnathidae indicate unique evolutionary traits among Araneoidea

Abstract

Nephilid systematics has been subject to several changes in the last years, and the use of non-classical characters could be useful for evolutionary considerations. In this study, we analyzed the mitotic chromosomes of two nephilid spiders, Nephila clavipes and Nephila sexpunctata, using standard staining, silver nitrate impregnation and C-banding techniques, aiming to discuss the chromosomal similarities of Nephilidae and Tetragnathidae, and chromosome evolution within Nephila and Nephilingis. The basic karyotype characteristics observed in these two species (2n♂ = 22 + X 1 X 2 0 and monoarmed chromosomes) were similar to those registered for most araneoid families, i.e., Araneidae, Linyphiidae, Nephilidae, Nesticidae and Tetragnathidae. However, the occurrence of both prominent secondary constrictions and nucleolar organizer regions (NORs) is a shared characteristic between Nephilidae and Tetragnathidae, considering that these regions were not observed in any other Araneoidea species cytogenetically examined. Furthermore, in the present study we showed that within Nephila and Nephilingis species, change in the number and location of NORs as well as in the quantity and distribution of constitutive heterochromatin were the main events responsible for chromosome evolution, and that these differences can be useful in the cytotaxonomy of this group.

Identification of sex chromosomes using genomic and cytogenetic methods in a range-expanding spider,Argiope bruennichi(Araneae: Araneidae)

“…minuta (Datta & Chatterjee, 1988), and A. pulchella (Bole-Gowda, 1958). This karyotype is the most common in analyzed species of the superfamily Araneoidea, and is probably an ancestral feature of this clade (Araujo et al, 2015). As in most other entelegyne spiders, the karyotype of A. bruennichi is formed by acrocentric chromosomes (Kořínková & Král, 2013); this karyotype structure can be considered ancestral for entelegynes (Král et al, 2006).…”

Identification of sex chromosomes using genomic and cytogenetic methods in a range-expanding spider, Argiope bruennichi (Araneae: Araneidae)

“…The same karyotype was found in two other Argiope species, namely A. minuta (Datta & Chatterjee, 1988), and A. pulchella (Bole-Gowda, 1958). This karyotype is the most common in analyzed species of the superfamily Araneoidea, and is probably an ancestral feature of this clade (Araujo et al ., 2015). As in most other entelegyne spiders, the karyotype of A. bruennichi is formed by acrocentric chromosomes (Kořínková & Král, 2013); this karyotype structure can be considered ancestral for entelegynes (Král et al ., 2006).…”