Gray Short-tailed Opossum

The Gray Short-tailed Opossum (Monodelphis domestica) is a small member of the Didelphidae family of opossums. It was the first marsupial to have its genome sequenced. It is naturally found in arboreal habitats in Bolivia, Brazil and Paraguay. The opossum is used as research model in science^[3], and is also frequently found in the exotic pet trade. It is also known as the Brazilian Opossum, Rainforest Opossum and in a research setting the Laboratory Opossum.

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Laboratory Opossum

The gray short-tailed opossum possesses several features that make in ideal research model particularly in studies of marsupials, as well as the immunological and developmental research on mammalian systems. It breeds relatively easily in laboratory settings and neonates are exposed and can be readily accessed because, unlike other marsupial species, females opossums lack a pouch: neonates simply cling to the teats. Opossums are born at a stage that is approximately equivalent to 13-15-day old fetal rats or 40-day old human embryos. Like other marsupials, the inadequacies of the neonates immune system function make it an ideal model for both transplant and cancer research, as well as general investigations into immune system development^[4]. Its genome was sequenced and a working draft published in May 2007:^[5] the decoding work, directed by MIT and Harvard, reveals the opossum to have between 18,000 and 20,000 protein-coding genes.

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