Résumé
The oriental rat or Rattus tanezumi is not common in the valley of Manipur and seem to be exclusively concentrated on the small hillock called, Karang located on the famous lake called The Loktak Lake of Manipur. Fifteen live specimens were trapped using Sherman’s wire traps from the area and brought to the laboratory as soon as possible. Morphometric, skull study was carried from nine specimens and cytological work was done using bone marrow cells by conventional colchicines-hypotonicair drying techniques with fifteen live specimens. Morphologically this species is very closed to Rattus rattus. Cytologically the species comprised of acrocentrics from chromosome numbers 1 to 13, small metacentric from chromosome numbers 14 to 20 in autosomes; and both X and Y were also acrocentrics and Y was the smallest in the genome. Only polymorphic chromosomes were numbers 15, 16 and 19 due to metacentric and submetacentrics. According to the karyotype of the rat, Rattus tanezumi is much primitive to the Rattus rattus species. This species in synonymous to either brunneusculus or sikkiminensis that has been reported from Manipur