The blue butterfly Polyommatus (Plebicula) atlanticus (Lepidoptera, Lycaenidae) holds the record of the highest number of chromosomes in the non-polyploid eukaryotic organisms

Abstract

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) Polyommatus 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, Polyommatus atlanticus is confirmed to possess the highest chromosome number among all the non-polyploid eukaryotic organisms.

Keywords: Acipenser; Amoeba proteus; Astacus; Aulacantha scolymantha; Lycaenidae; Ophioglossum; Pacifastacus; Plebicula; Polyommatus; chromosome number; karyotype evolution; linkage group; vizcacha rat.

Figure 1.

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.