期刊
DIVERSITY-BASEL
卷 14, 期 10, 页码 -出版社
MDPI
DOI: 10.3390/d14100874
关键词
holokinetic chromosomes; gomphids X chromosome evolution; sex-determination systems; Aphylla; Phyllocycla
资金
- National Council of Scientific and Technological Research (CONICET) [11220200102115CO]
This study investigated the meiosis of three gomphid species from Argentina and found a positive correlation between the size of the X chromosome and the amount of heterochromatin. The results suggest that the large size of the X chromosome may be due to the accumulation of repetitive DNA and heterochromatin rather than fusion.
In most Anisoptera families, the modal diploid number is 25 in males (24 autosomes + X), and the X chromosome is one of the smallest elements of the complement. The family Gomphidae is an exception, as it has a modal diploid number of 23 (22 + X), and the X chromosome is the largest of the complement and of medium-to-large size in many species. We studied the meiosis of three gomphid species from Argentina: Aphylla cf. distinguenda (Campion, 1920), Phyllocycla propinqua Belle, 1972 and Phyllocycla sp. Chromosome number is 2n = 23, n = 11 + X, except for Phyllocycla propinqua, showing n = 10 + X. The X chromosome of these species is medium-sized and presents heteropyknotic blocks of different sizes. Despite the small number of gomphid species analysed, there is a clear trend of increasing size of the X chromosome with the increasing amount of heterochromatin. Our results, together with those from the literature, suggest that its large size might have been due to a progressive accumulation of repetitive DNA and heterochromatinisation and not to fusion, as previously suggested. This led us to propose that the ancestral number coincided with the modal number of Gomphidae. A revision of the derived sex-determining systems in Odonata is also provided.
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