A karyotypic analysis of the lesser Malay chevrotain, Tragulus javanicus (Artiodactyla: Tragulidae)

Chevrotains are small forest-dwelling ruminants of the family Tragulidae. The chromosome number of the lesser Malay chevrotain was determined to be 2n = 32, NF = 64, G- and Q-banding allowed the identification of homologous chromosomes, and C-banding demonstrated the presence of pericentromeric, telomeric and interstitial constitutive heterochromatin. Q-band comparisons with domestic cattle revealed relatively few monobrachial chromosome band homologies. However, the smallest biarmed autosome of the chevrotain, chromosome 15, was determined to be cytogenetically homologus with the acrocentric chromosome 19 of cattle. A molecular cytogenetic analysis confirmed this putative chromosomal homology. In fact, molecular cytogenetic analyses indicate complete conservation of synteny among mouse deer chromosome 15, domestic cattle chromosome 19, domestic pig chromosome 12 and human chromosome 17. In the light of these molecular cytogenetic data and since mouse deer chromosome 15 is submetacentric and appears homologous in banding to submetacentric chromosome 12 of the domestic pig, these outgroup comparisons indicate that the acrocentric condition of cattle chromosome 19 has been derived by inversion. Since this derivative condition is present in the Antilocapridae, Bovidae, Cervidae and Giraffidae, it is a chromosomal synapomorphy that unites these advance ruminant families within the Artiodactyla.