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Corresponding author: Vladimir Lukhtanov ( lukhtanov@mail.ru ) Academic editor: Valentina G. Kuznetsova
© 2015 Vladimir Lukhtanov.
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Citation:
Lukhtanov VA (2015) The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms. Comparative Cytogenetics 9(4): 683-690. https://doi.org/10.3897/CompCytogen.v9i4.5760
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The blue butterfly species Polyommatus (Plebicula) atlanticus (Elwes, 1906) (Lepidoptera, Lycaenidae) is known to have a very high haploid number of chromosomes (n= circa 223). However, this approximate count made by Hugo de Lesse 45 years ago was based on analysis of a single meiotic I metaphase plate, not confirmed by study of diploid chromosome set and not documented by microphotographs. Here I demonstrate that (1) P. atlanticus is a diploid (non-polyploid) species, (2) its meiotic I chromosome complement includes at least 224-226 countable chromosome bodies, and (3) all (or nearly all) chromosome elements in meiotic I karyotype are represented by bivalents. I also provide the first data on the diploid karyotype and estimate the diploid chromosome number as 2n=ca448-452. Thus, P. atlanticus is confirmed to possess the highest chromosome number among all the non-polyploid eukaryotic organisms.
Acipenser , Amoeba proteus , Astacus , Aulacantha scolymantha , chromosome number, karyotype evolution, linkage group, Lycaenidae , Ophioglossum , Pacifastacus , Plebicula , Polyommatus , vizcacha rat
Trends and mechanisms of chromosome number and chromosome structure changes are currently a matter of a sharp discussion (
Comparative analysis of chromosomal data is a promising way for understanding the patterns of karyotype evolution (
The aim of this study is cytogenetic reinvestigation and documentation of P. atlanticus karyotype with a special consideration of diploid chromosome set of this species.
The studied species is often mentioned in the literature as a member of the genus Lysandra Hemming, 1933 (e.g.
The haploid chromosome number n=ca 224–226 was found in MI cells of three studied individuals (Fig.
Male karyotype of Polyommatus (Plebicula) atlanticus, sample NK02A032. a MI plate b chromosome count in MI plate: red dots indicate distinct separate entities, blue dots indicate doubtful entities, n=224 red dots + 2 blue dots c diploid chromosome set observed in male asynaptic meiosis d chromosome number count in diploid chromosome set; at least 434 entities can be distinguished. Bar = 10 μm.
Previously, the chromosome number was estimated in P. atlanticus as n=ca217-223 (
In eukaryotic organisms the highest number of chromosomes has been so far reported in radiolarian species, e.g. in Aulacantha scolymantha Haeckel, 1862 (Cercozoa, Aulacanthidae) there are more than 2000 chromosomes (
500 chromosomes were reported for asexual lobose amoebae, Amoeba proteus (Pallas, 1766) (Amoebozoa, Amoebidae) (
Very high chromosome numbers are known in some plants, e.g. in ferns of the genus Ophioglossum Linnaeus, 1753 (Pteridophyta, Ophioglossaceae) n=120–720 (
In vertebrate animals the highest chromosome number (372 elements in mitotic cell divisions) is known in sturgeon Acipenser brevirostrum Lesueur, 1818 (Acipenseriformes, Acipenseridae) (
According to
The data obtained indicate that P. atlanticus is a diploid (not polyploid) species since it possesses double (not multiple) number of chromosomes that can be individually recognized: one pair of large and one pair of medium chromosomes. Thus, P. atlanticus is confirmed to have the highest chromosome number among all the non-polyploid eukaryotic organisms.
I thank Roger Vila, Santiago Ramirez and Nikolai Kandul for providing collected specimens. I thank Valentina Kuznetsova, Vladimir Gokhman, Nikolai Kandul and Vladimir Trifonov for valuable comments. The financial support for this study was provided by the grant from the Russian Science Foundation N 14-14-00541 to Zoological Institute of the Russian Academy of Sciences.