{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,12]],"date-time":"2026-04-12T14:53:07Z","timestamp":1776005587307,"version":"3.50.1"},"reference-count":70,"publisher":"Pensoft Publishers","issue":"4","license":[{"start":{"date-parts":[[2021,11,3]],"date-time":"2021-11-03T00:00:00Z","timestamp":1635897600000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["CCG"],"abstract":"<jats:p>The American dragonfly genus <jats:italic>Orthemis<\/jats:italic> Hagen, 1861 is mainly found in the Neotropical region. Seven of 28 taxonomically described species have been reported from Argentina. Chromosome studies performed on this genus showed a wide variation in chromosome number and a high frequency of the neoXY chromosomal sex-determination system, although the sexual pair was not observed in all cases. This work analyzes the spermatogenesis of <jats:italic>Orthemis discolor<\/jats:italic> (Burmeister, 1839), <jats:italic>O. nodiplaga<\/jats:italic> Karsch, 1891 and <jats:italic>O. ambinigra<\/jats:italic> Calvert, 1909 in individuals from the provinces of Misiones and Buenos Aires, Argentina. <jats:italic>Orthemis discolor<\/jats:italic> has 2n=23, n=11+X and one larger bivalent. <jats:italic>Orthemis nodiplaga<\/jats:italic> exhibits the largest chromosome number of the order, 2n=41, n=20+X and small chromosomes. <jats:italic>Orthemis ambinigra<\/jats:italic> shows a reduced complement, 2n=12, n=5+neo-XY, large-sized chromosomes, and a homomorphic sex bivalent. Fusions and fragmentations are the main evolutionary mechanisms in Odonata, as well as in other organisms with holokinetic chromosomes. <jats:italic>Orthemis nodiplaga<\/jats:italic> would have originated by nine autosomal fragmentations from the ancestral karyotype of the genus (2n=22A+X in males). We argue that the diploid number 23 in <jats:italic>Orthemis<\/jats:italic> has a secondary origin from the ancestral karyotype of family Libellulidae (2n=25). The complement of <jats:italic>O. ambinigra<\/jats:italic> would have arisen from five autosomal fusions and the insertion of the X chromosome into a fused autosome. C-banding and DAPI\/CMA<jats:sub>3<\/jats:sub> staining allowed the identification of the sexual bivalent, which revealed the presence of constitutive heterochromatin. We propose that the chromosome with intermediate C-staining intensity and three medial heterochromatic regions corresponds to the neo-Y and that the neo-system of this species has an ancient evolutionary origin. Moreover, we discuss on the mechanisms involved in the karyotypic evolution of this genus, the characteristics of the neo sex-determining systems and the patterns of heterochromatin distribution, quantity and base pair richness.<\/jats:p>","DOI":"10.3897\/compcytogen.v15.i4.68761","type":"journal-article","created":{"date-parts":[[2021,11,3]],"date-time":"2021-11-03T07:43:30Z","timestamp":1635925410000},"page":"355-374","source":"Crossref","is-referenced-by-count":5,"title":["High karyotypic variation in Orthemis Hagen, 1861 species, with insights about the neo-XY in Orthemis ambinigra Calvert, 1909 (Libellulidae, Odonata)"],"prefix":"10.3897","volume":"15","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2511-8067","authenticated-orcid":true,"given":"Liliana M.","family":"Mola","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mar\u00eda Florencia","family":"Fourasti\u00e9","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Silvia Susana","family":"Agopian","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"2258","published-online":{"date-parts":[[2021,11,3]]},"reference":[{"issue":"3","key":"68761_B1","first-page":"45","article-title":"An exceptionally high chromosome number in Orthemis nodiplaga Kersch (Anisoptera, Libellulidae).","volume":"2","author":"Agopian","year":"1984a","journal-title":"Notulae Odonatologicae"},{"key":"68761_B2","author":"Agopian","year":"1984b"},{"key":"68761_B3","doi-asserted-by":"publisher","DOI":"10.1080\/00087114.1988.10797849"},{"key":"68761_B4","doi-asserted-by":"publisher","DOI":"10.1007\/s12041-011-0108-4"},{"key":"68761_B5","doi-asserted-by":"publisher","DOI":"10.3897\/compcytogen.v14.i4.53688"},{"key":"68761_B6","doi-asserted-by":"publisher","DOI":"10.1007\/s10709-010-9458-8"},{"key":"68761_B7","doi-asserted-by":"publisher","DOI":"10.1665\/034.019.0207"},{"key":"68761_B8","doi-asserted-by":"publisher","DOI":"10.14411\/eje.2014.047"},{"key":"68761_B9","doi-asserted-by":"publisher","DOI":"10.1038\/sj.hdy.6800697"},{"key":"68761_B10","doi-asserted-by":"publisher","DOI":"10.1139\/g68-029"},{"key":"68761_B11","author":"Cumming","year":"1964","journal-title":"Cytogenetic studies in the order Odonata."},{"key":"68761_B12","doi-asserted-by":"publisher","DOI":"10.1080\/00087114.2008.10589610"},{"issue":"4","key":"68761_B13","first-page":"9","article-title":"Orthemis ferruginea \u2013 An adventure in Caribbean biogeography.","volume":"7","author":"Donnelly","year":"1995","journal-title":"Argia"},{"key":"68761_B14","first-page":"5","article-title":"Male germ cell chromosomes of thirty-two Brazilian dragonflies.","volume":"8","author":"Ferreira","year":"1979","journal-title":"Odonatologica"},{"issue":"1","key":"68761_B15","first-page":"32","article-title":"Comparative cytogenetic analysis of karyotype morphology and organization in males of species Libellula depressa L. and L. fulva M\u00fcll. 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