Which mammal has the highest known number of chromosomes?

The red viscacha rat (Tympanoctomys barrerae) has been found to have 102 chromosomes, the highest known number among mammals. Both the aquatic rat (Anotomys leander) and the Pittier's crab-eating rat share a chromosome number of 92, which was previously thought to be the highest among mammals. Humans (Homo Sapiens) have just 46, a number it shares with Reeves's muntjac (Muntiacus reevesi) and the Sable antelope (Hippotragus niger). In humans, two of those chromosomes are sex chromosomes a fact oddly shared with dogs (Canis lupus familiaris) who, however, have 76 autosomal chromosomes to the human 44. These numbers hardly reach the highest in the Animal Kingdom, with the Agrodiaetus butterfly at 268.

Chromosomes, found in the cells of all living organisms contain the their genetic code in pairs of nucleic acids making up the double helix of DNA. They can be viewed through a microscope. The number of the chromosomes as well as their physical appearance are described as a Karyotype (a human karyotype is in the photograph) and the study of these is part of cytogenetics.

More Info: en.wikipedia.org

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Pat Askew

The mitotic and meiotic chromosomes of the semi-aquatic rodent Ichthyomys pittieri (Rodentia, Cricetinae) from Venezuela were analyzed by means of conventional staining and several banding techniques. The diploid chromosome number of this rare species is 2n = 92, which is the highest value known for mammals.

dcgustin

Aquatic Rat: (Anotomys leander) has 92 chromosomes ... the same number as the Pittier's crab-eating Rat (Ichthyomys pittieri) ... it's a tie !!! http://www.wow.com/wiki/List_of_organisms_by_chromosome_count

William Laughlin

Stephanie Fox, A crab is not a mammal.

Nikki Proctor

stevemanning, a rat is a mammal.

stevemanning

Question states "mammals". This Q&A needs work.

Steve Edwards

Cindy Austria, your google source is out of date!

Cindy Austria

According to Google : Format: AbstractSend to Cytogenet Cell Genet. 1988;49(4):305-8. On the highest chromosome number in mammals. Schmid M1, Fernández-Badillo A, Feichtinger W, Steinlein C, Roman JI. Author information Abstract The mitotic and meiotic chromosomes of the semiaquatic rodent Ichthyomys pittieri (Rodentia, Cricetinae) from Venezuela were analyzed by means of conventional staining and several banding techniques. The diploid chromosome number of this rare species is 2n = 92, which is the highest value known for mammals. It is assumed that this exceptionally high chromosome number is the result of repeated centric fissions. The karyotype of I. pittieri was compared with that of Anotomys leander, for which a diploid number of 2n = 92 has also been reported. The karyological relationships existing within the Neotropical Cricetidae are summarized.