Chromosomal diversity in three species of Lycosa Latreille, 1804 (Araneae, Lycosidae): Inferences on diversification of diploid number and sexual chromosome systems in Lycosinae

Abstract Lycosa is one of the most speciose genera in Lycosidae, including species with different sexual chromosome systems (SCS). We carried out cytogenetic analyses in three species of Lycosa, revealing that L. erythrognatha and L. sericovittata share 2n ♂ = 22 and SCS X1X20 while L. gr. nordenskjoldi presents 2n ♂ = 19 and SCS XO, composed only of acrocentric chromosomes. All species shared pericentromeric heterochromatin. Nonetheless, one specimen of L. sericovittata carried two chromosomes with terminal heterochromatin and L. gr. nordenskjoldi showed four chromosomes with interstitial heterochromatin plus another chromosome with terminal C-bands. The pericentromeric heterochromatin of all species as well as the terminal heterochromatic blocks in L. sericovittata were CMA3+. The 18S rDNA sites varied in number and type of bearing chromosomes both at inter and intrapopulational levels, with the highest variation in L. gr. nordenskjoldi. These differences may be related to gene dispersal due to the influence of transposition elements and translocation events. Despite these variations, all species shared ribosomal sites in pair 5. This study demonstrated intra and interspecific chromosomal variability of Lycosa, suggesting that chromosomal rearrangements are related to the diversification of diploid number and SCS in this group of spiders.摘要 狼蛛属（Lycosa）是狼蛛科（Lycosidae）中物种多样性最高的属之一，涵盖具有不同性染色体系统（sexual chromosome systems, SCS）的物种。本研究对3种狼蛛属物种开展了细胞遗传学分析，结果显示：红颚狼蛛（L. erythrognatha）与丝带狼蛛（L. sericovittata）的雄性二倍体染色体数（2n ♂）均为22，性染色体系统为X₁X₂0；而诺登斯基尔登狼蛛类群（L. gr. nordenskjoldi）的雄性二倍体染色体数为19，性染色体系统为XO，且所有染色体均为近端着丝粒染色体。所有供试物种均具有着丝粒旁异染色质。值得注意的是，1只丝带狼蛛个体携带2条带有末端异染色质的染色体，诺登斯基尔登狼蛛类群则存在4条带有居间异染色质的染色体，另有1条染色体带有末端C带。所有物种的着丝粒旁异染色质以及丝带狼蛛的末端异染色质区域均为嗜铬霉素A3阳性（CMA3+）。18S核糖体DNA（18S rDNA）位点的数量及其所在染色体类型在种群间和种群内均存在差异，其中诺登斯基尔登狼蛛类群的变异程度最高。此类差异可能与转座因子和易位事件介导的基因扩散有关。尽管存在上述变异，所有供试物种均在第5号染色体对上共享核糖体DNA位点。本研究揭示了狼蛛属物种的种内与种间染色体变异，表明染色体重排与该类蜘蛛的二倍体数目及性染色体系统的分化密切相关。