First Description of the Karyotype and Sex Chromosomes in the Komodo Dragon <b><i>(Varanus komodoensis)</i></b>

Abstract

The Komodo dragon (Varanus komodoensis) is the largest lizard in the world. Surprisingly, it has not yet been cytogenetically examined. Here, we present the very first description of its karyotype and sex chromosomes. The karyotype consists of 2n = 40 chromosomes, 16 macrochromosomes and 24 microchromosomes. Although the chromosome number is constant for all species of monitor lizards (family Varanidae) with the currently reported karyotype, variability in the morphology of the macrochromosomes has been previously documented within the group. We uncovered highly differentiated ZZ/ZW sex microchromosomes with a heterochromatic W chromosome in the Komodo dragon. Sex chromosomes have so far only been described in a few species of varanids including V. varius, the sister species to Komodo dragon, whose W chromosome is notably larger than that of the Komodo dragon. Accumulations of several microsatellite sequences in the W chromosome have recently been detected in 3 species of monitor lizards; however, these accumulations are absent from the W chromosome of the Komodo dragon. In conclusion, although varanids are rather conservative in karyotypes, their W chromosomes exhibit substantial variability at the sequence level, adding further evidence that degenerated sex chromosomes may represent the most dynamic genome part.

Genome of the Komodo dragon reveals adaptations in the cardiovascular and chemosensory systems of monitor lizards

“…A third individual from Gran Canaria was used for PacBio DNA sequencing. The Komodo dragon genome is distributed across 20 pairs of chromosomes, comprising eight pairs of large chromosomes and 12 pairs of microchromosomes 9 , 10 . De novo assembly was performed with a combination of 10x Genomics linked-read sequencing, Bionano optical mapping data, PacBio sequencing, and Oxford Nanopore MinIon sequencing (see Methods ).…”

Cytogenetics of the Javan file snake (Acrochordus javanicus) and the evolution of snake sex chromosomes

“…Chromosomes were stained by Giemsa and C‐banding to visualize blocks of constitutive heterochromatin, according to Sumner () with slight modifications as described in Johnson Pokorná et al. ().…”

A high-resolution, chromosome-assigned Komodo dragon genome reveals adaptations in the cardiovascular, muscular, and chemosensory systems of monitor lizards

“…We obtained DNA from peripheral blood of two male individuals housed at Zoo Atlanta: Slasher, a male offspring of the first Komodo dragons given as gifts in 1986 to US President Reagan from President Suharto of Indonesia, and Rinca, a juvenile male (Figure 1A). The V. komodoensis genome is distributed across 20 pairs of chromosomes, comprising eight pairs of large chromosomes and 12 pairs of microchromosomes 13,14 . De novo assembly was performed using 57X coverage of 10x Genomics linked-read sequencing data to generate an initial assembly with a scaffold N50 of 10.2 Mb and a contig N50 of 95 kb.…”