Comparative cytogenetics of the African elephant <i>(Loxodonta africana)</i> and Asiatic elephant <i>(Elephas maximus)</i>

Abstract

G- and C-banded karyotypes of the two extant species of the mammalian order Proboscidea are presented for the first time. Chromosome complements were 2n = 56 in both Loxodonta africana and Elephas maximus. Comparisons between the species demonstrated a high level of chromosome band homology, with 26 conserved autosomal pairs. The normal diploid karyotype of L. africana had 25 acrocentric/telocentric and two metacentric/submetacentric autosomal pairs. E. maximus differed by having one less acrocentric and one additional submetacentric pair due to either a heterochromatic arm addition or deletion involving autosomal pair 27. Several acrocentric autosomes of L. africana exhibited small short arms that were absent in homologous chromosomes of E. maximus. The X chromosomes in both species were large submetacentric elements and were homologous. However, the small acrocentric Y chromosomes differed; in E. maximus it was slightly larger and had more distinct G-bands than its counterpart in L. africana. Extant Elephantidae appear to be relatively conservative in their rates of chromosomal change compared to some other mammalian families. The high-quality banded karyotypes presented here should prove useful as references in future chromosome analyses of elephant populations and in comparative cytogenetic studies with other ungulate orders.

Towards the delineation of the ancestral eutherian genome organization: comparative genome maps of human and the African elephant (Loxodonta africana) generated by chromosome painting

“…The G-banding pattern of chromosomes derived from the elephant cell culture used in this study matches that of the published karyotype (Houck et al 2001). The cell line displayed polymorphisms in the length of the short arms of the acrocentric chromosomes LAF 2, 5, 6, 7, 12, 19 and 23.…”

“…However, sequence homologies in repetitive DNA are highly unlikely between such distantly related mammals. A comparison with the C-banded karyotype (Houck et al 2001) shows that the HSA 21 signal is located in a euchromatic region between two small C-band positive blocks and therefore is unlikely to be due to repetitive sequences. This association has not been reported for other species and therefore constitutes chromosomal rearrangement linking the two Afrotherian species.…”

“…There are several classical cytogenetic reports published on African elephant chromosomes (e.g. Hungerford et al 1966;Thurig 1970) but only recently have elephant karyotypes been analysed by chromosome banding (Houck et al 2001). Houck and collaborators reported a high level of chromosome band homology between the African elephant and the Asian elephant (Elephas maximus).…”

“…The forest elephants have not yet been studied cytogenetically. The existing chromosome banding studies (Houck et al 2001) indicate, however, a strong conservation of elephant karyotypes since the evolutionary separation of Elephas maximus and Loxodonta africana 4-7 Myr ago (Thomas et al 2000;Vignaud et al 2002). After the submission of this manuscript, a Zoo-FISH study of aardvark and elephant genomes was published .…”

The Chromosomes of Afrotheria and Their Bearing on Mammalian Genome Evolution

“…manatus latirostris (2n = 48) [Assis et al, 1988;Gray et al, 2002]. GTG-banded karyotypes of 2 Proboscidea, the African and Asian elephants ( Loxodonta africana and Elephas maximus , respectively) were also described and compared, allowing the detection of a high homology between both karyotypes [Houck et al, 2001]. Three of the 5 recognized hyrax species had their complements reported after GTG-banding: Procavia capensis, Dendrohyrax arboreus and Heterohyrax brucei .…”