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Meiotic Analysis of Gomphidae Species Sheds Light on the Large X Chromosome of the Family (Anisoptera, Odonata)

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 complemen...

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Bibliographic Details
Published in:Diversity (Basel) 2022-10, Vol.14 (10), p.874
Main Authors: Mola, Liliana M, Rebagliati, Pablo J, Fourastié, María F, Agopian, Silvia S
Format: Article
Language:English
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Summary: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.
ISSN:1424-2818
1424-2818
DOI:10.3390/d14100874