Each type of animal has a system of digestion are different, as for the type of rodentia in general has its own character such as the stomach is divided into three parts, namely pars cardia, fundus, and pars pylorica, then to the gut, jejenum, duodenum and cecum, colon (colon) adjacent to the ileum ascending colon, transverse, descenden, and sigmoideum, then the rectum as the ultimate gut and excreted through the anus. In animals, this type of rodentia own digestive glands that help the digestion process such as the liver and pancreas.
Type rodentia in its development is one example that is undergoing a process of change in the digestion tract is laos rock rat. These animals included in herbivores characterized by a significant capacity in the digestive tract, it is very important for microbial degradation in the intestines. Food vegetables that will long be in the gastrointestinal tract, large herbivores channel comparable to that small. This causes, nutrition strategies on small mammals is directed to the selectivity of great food when eating certain parts of the vegetation. The maximum volume of the digestive tract usually does not exceed 25% of the body weight herbivorous mammals itself. Volume gastrointestinal tract of the Laotian rock rat according to the indicators that strengthens as absolute herbivores. This is also evidenced by the small surface pars pylorica, the absence vesica fellea, ampulla duodeni enlarged, and their intestines spiral loops which are all characteristics typical for herbivorous rodents.
Laotian rock rat is a small rodent. The average length of the body is 258.0 mm (238.0 to 290.0 mm). The length of the entire gastrointestinal tract can reach 1500 mm, exceeding the body length up to 4.8 to 6.0 times. Massa entire colon is 25-27% of the body mass. Oesophageal size is rather short resemble narrow pipe. At rest, a length not exceeding 50 mm, a width of 6 mm, compact abdominal cavity located in the body and organs are sacculated along curvatura ventriculi major. Laos rock rat have different digestive tract of mice that exist today when compared with certain digestive tract by developing hindgut fermentation, in addition to the large foregut system has never been found in other mice except for the Laotian rock rat. Foregut fermentation was typical in laos rock rat for the other types of mice using hindgut fermentation.
Laos stomach in rats stone itself has three parts, among others saccus gastricus (sacciform forestomach), tubus gastricus (tubiform forestomach), and pars pylorica (hindstomach), the parts are also found in all mammals. Pars pylorica narrower and shorter than the other parts. On average, the length is 43.75 mm ± 5:15 and 4:28 ± 0:17 mm wide. Pylorica pars shape resembles hindstomach certain marsupials and primates folivorous. The surface area of pars pylorica is about 4 to 10% of the total surface area inside the abdomen depending on the volume of digesta. Intestinal structure confirms the major role in the digestive tract of mice. The small intestine to be highly developed, it is based on the extension of the surface area of absorption from the small intestine.
Long-term evolution of the foregut in wet tropical forest conditions gain a significant advantage in digesting the food. In this small mammal has a system clogged intestines can not use the leaves of tropical trees as the basic source of their food. Conversely, small foregut fermenters can not digest grass effectively, this is the reason why these mammals do not live in open habitats where there are monocots. Belly up in the foregut of small mammals seems to be the main adaptations required to improve digestion time in the vegetative parts of the plant. Laotian rock rat body weight of less than 500 g. Folivorous smallest rodent and mammalian herbivores smallest, has an enlarged forestomach.
Although the primary rat and primate eating fruits and seeds, there is the possibility that forestomach be one of the first adaptation of mammals to eat the plants, especially the soft plant foods. It is only found in tropical regions where the climate cost of maintaining energy metabolism were minimal, thus unable to answer why the early foregut mammals have a small body size and a great adaptive radiation of Diatomyidae in tropical forest occurs in the historical period. Such modifications typically associated with changes in body and organ dimensions rather than the A convergent origin of some structures of various digestive system can be hidden. However, morphological adaptations to herbivores and the composition of the intestinal microbiota proved to represent convergent evolution among mammals with similar intestinal occupy the same trophic niche and the radical changes of the primary structure of the organism system.
Convergent evolution seems to explain the fact that the structure of the digestive system does not resemble the laos rock rat rats were still there, but it resembles a group of mammals such as marsupials. Tooth pattern has been found in Laotian rock rat, which is a convergence in the structure of the teeth from the Miocene mammalian offspring folivorous also seen in the early part of the digestive system. Typically, a convergent development of population or species response to certain environmental conditions are similar this adaptive zones animals. At the end of the Miocene marked the start of global cooling, drying and seasonal climate. Changes affecting the composition and distribution of vegetation. This resulted in changes in the composition and abundance of herbivorous species, as well as modification of their habitus and the structure of the digestive tract. A number of fruit eaters and arboreal mammals are also reduced. Perhaps, teeth and foregut small mammalian system was not effective for digesting plants monocots which accumulate huge amounts of lignin, cellulose and sand. Causing mammalian foregut fermentation pregastric with less competitive.
These animals maintain a simple unilocular stomach, especially in the Laotian rock rat, for specialization weak their foregut region, then the mice developed intestinal system сolon-cecum adapted to digest vegetable diet. Laotian rock rat has a groove in the stomach, small mammals Some breeds with foregut fermentation able to survive in the tropical forests. The main evolution in the Laotian rock rat is the transition from high calorie foods into the low green vegetables.
This article is based on journal review.
Journal are :
Campbell, Neil A., Jane B. Reece., And Lawrence G. Mitchell. 2004. Biology, Fifth Edition, Volume 3. Erland. Jakarta.
Laakkonen, J. Tuomas K., Ian J. C., Jukka J., Timo S., Khamsavath K. & Jean-Pierre H. 2014. Gastrointestinal and dental morphology of herbivorous Mammals: where does the Laotian rock rat fit ?. Ann. Zool. Fennici, 51: 153-161.
Scopin, A.E., A.P. Saveljev, N.A. Suntsova, S. Gnophanxay, A.N. Tikhonov and A.V. Abramov. 2013 Digestive system of the Laotian rock rat Laonastes aenigmamus (rodentia: diatomyidae) from the evolutionary viewpoint. Proceedings of the Zoological Institute RAS, 315 (1): 3-18.
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