Abstract
Cytogenetic studies of the family Lycosidae (Arachnida: Araneae) are scarce. Less than 4% of the described species have been analyzed and the male haploid chromosome numbers ranged from 8+X1 X 2 to 13+X1 X 2. Species formerly classified as were the most studied ones. Our aim in this work was to perform a comparative analysis of the meiosis in Lycosa erythrognatha Lucas, Lycosa pampeana Holmberg and Schizocosa malitiosa (Tullgren). We also compared male and female karyotypes and characterized the heterochromatin of L. erythrognatha. The males of the three species had 2n = 22, n = 10+X1X2, all the chromosomes were telocentric and there was generally a single chiasma per bivalent. In Lycosa pampeana, which is described cytogenetically for the first time herein, the bivalents and sex chromosomes showed a clustered arrangement at prometaphase I. The comparison of the male/female karyotypes (2n = 22/24) of Lycosa erythrognatha revealed that the sex chromosomes were the largest of the complement and that the autosomes decreased gradually in size. The analysis of the amount, composition and distribution of heterochromatin with C-banding and staining with DAPI- and CMA3 - showed that Lycosa erythrognatha had little GC-rich heterochromatin in the pericentromeric region of all chromosomes. In addition, the actual occurrence of the genus in the Southern Hemisphere is discussed.
Highlights
Two of them belonged to the genus Schizocosa Chamberlin 1904 and the remaining eight to the genus Lycosa Latreille 1804 (Table 1)
We found a 2n = 22 (20+X1X2, male) in Schizocosa malitiosa
This species had a karyotype with all telocentric chromosomes, with the sex chromosomes being the largest of the complement and chiasmata mainly at interstitial or distal positions
Summary
Cytogenetic studies of the family Lycosidae (Arachnida, Araneae) are scarce and were performed in less than 4% of the 2324 known species (Platnick, 2008). Most of the analyzed species had only telocentric or acrocentric chromosomes, which ranged from 2n = 18, n = 8+X1X2 (male) to 2n = 28/30 (male/female), n = 13+X1X2 (male). The 2n = 28/30, which is present in 50% of the analyzed species, is probably the modal diploid number of the family. The derived systems are: X0 in Lycosa barnesi, L. nordenskjoldi, Wadicosa quadrifera and an unidentified species of Schizocosa 2 in Table 1); X1X2X3 in an unidentified species of Lycosa Most cytological studies have been performed in species formerly classified as Lycosa and the most common male haploid chromosome number was n = 13+X1X2 in the Northern Hemisphere species. The Southern Hemisphere species presented complements with n = 10+X1X2 (males) or derived from it (Table 1)
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