Placental Ruminants and Herbivorous Marsupials of Australia Essay

Placental Ruminants and Herbivorous Marsupials of Australia The marsupial animal species that have evolved on the isolated continent of Australia are unique compared to the rest of the animal kingdom in many ways due to the harsh and distinctive environment found on the continent. The major area of marsupial biology that distinguishes them from all other eutherian mammals is their mode of reproduction. However, it can be said that there are many other areas in which unique differences can be seen between marsupials and eutherian mammals; one such area of adaptation is in the anatomy and physiology of digestion, which distinguishes them from many other similar animals worldwide. The foregut fermenters, such as kangaroos and wallabies, evolved in regions of poor forage quality to be able to extract the most nutrients out of the poorest feeds. Fermentation in the foregut has many advantages over hindgut fermentation, which is seen in marsupials such as the koalas and wombats. The anatomy and physiology of the digestive tracts of both types of fermenters, however, are uniquely suited to their individual modes of nutrition. It can be suggested that the foregut fermenters of the marsupials are very similar to the eutherian ruminants, as both types of adaptations are designed to increase fiber digestibility and increase nutrient absorption. However, there are many major differences between the two groups. Ruminants have developed a four-chambered stomach system, which is not seen in the marsupials, as well as a rumination cycle which allows for the rechewing of previously ingested meals. While regurgitation may be evident in marsupials, it is, however, not analogous to rumination, and is instead called â€Å"merycism.†... .... 23 March 2004. Milewski, A.V. and R.E. Diamond. 2000. Why are very large herbivores absent from Australia? A new theory of micronutrients. Journal of Biogeography. 27(4): 957-978. Russell, J.B. 1988. â€Å"Ecology of Rumen Microorganisms: Energy Use.† In Dobson, Alan, and Marjorie J. Dobson, eds. Aspects of Digestive Physiology in Ruminants: Proceedings of a Satellite Symposium of the 30th International Congress of the International Union of Physiological Sciences. Cornell University Press: Ithaca, NY, pg 74-98. Stevens, C.E. and I.D. Hume. 1995. Comparative Physiology of the Vertebrate Digestive System. Cambridge: Cambridge University Press. Strahan, Ronald, ed. 1995. The mammals of Australia. Smithsonian Institution Press: Washington, DC. Van Soest, Peter J. 1994. Nutritional ecology of the ruminant. Ithaca: Comstock Publishing. Placental Ruminants and Herbivorous Marsupials of Australia Essay Placental Ruminants and Herbivorous Marsupials of Australia The marsupial animal species that have evolved on the isolated continent of Australia are unique compared to the rest of the animal kingdom in many ways due to the harsh and distinctive environment found on the continent. The major area of marsupial biology that distinguishes them from all other eutherian mammals is their mode of reproduction. However, it can be said that there are many other areas in which unique differences can be seen between marsupials and eutherian mammals; one such area of adaptation is in the anatomy and physiology of digestion, which distinguishes them from many other similar animals worldwide. The foregut fermenters, such as kangaroos and wallabies, evolved in regions of poor forage quality to be able to extract the most nutrients out of the poorest feeds. Fermentation in the foregut has many advantages over hindgut fermentation, which is seen in marsupials such as the koalas and wombats. The anatomy and physiology of the digestive tracts of both types of fermenters, however, are uniquely suited to their individual modes of nutrition. It can be suggested that the foregut fermenters of the marsupials are very similar to the eutherian ruminants, as both types of adaptations are designed to increase fiber digestibility and increase nutrient absorption. However, there are many major differences between the two groups. Ruminants have developed a four-chambered stomach system, which is not seen in the marsupials, as well as a rumination cycle which allows for the rechewing of previously ingested meals. While regurgitation may be evident in marsupials, it is, however, not analogous to rumination, and is instead called â€Å"merycism.†... .... 23 March 2004. Milewski, A.V. and R.E. Diamond. 2000. Why are very large herbivores absent from Australia? A new theory of micronutrients. Journal of Biogeography. 27(4): 957-978. Russell, J.B. 1988. â€Å"Ecology of Rumen Microorganisms: Energy Use.† In Dobson, Alan, and Marjorie J. Dobson, eds. Aspects of Digestive Physiology in Ruminants: Proceedings of a Satellite Symposium of the 30th International Congress of the International Union of Physiological Sciences. Cornell University Press: Ithaca, NY, pg 74-98. Stevens, C.E. and I.D. Hume. 1995. Comparative Physiology of the Vertebrate Digestive System. Cambridge: Cambridge University Press. Strahan, Ronald, ed. 1995. The mammals of Australia. Smithsonian Institution Press: Washington, DC. Van Soest, Peter J. 1994. Nutritional ecology of the ruminant. Ithaca: Comstock Publishing.