Evolution of Karyotype and Sex Chromosomes in Two Families of Haplogyne Spiders, Filistatidae and Plectreuridae

Abstract

Spiders belong to one of the most diverse animal orders. One of the 3 primary clades of spiders are araneomorphs, which are divided into 2 groups, haplogynes and entelegynes.

Haplogyne cytogenetics is not satisfactorily understood. Several families of haplogynes exhibit an unusual X 1 X 2 Y sex chromosome system, which generally comprises 2 large metacentric X chromosomes and 1 metacentric Y microchromosome.

These chromosomes display a specific achiasmatic mode of end-to-end pairing during male meiosis. In our study, we revealed an X 1 X 2 Y system in the family Plectreuridae.

Furthermore, we analyzed the karyotype evolution of plectreurids as well as Filistatidae, another family with an X 1 X 2 Y system. We also determined the pattern of nucleolus organizer regions (NORs) by means of fluorescence in situ hybridization for selected representatives of these groups.