Digestion is the process in which food is broken down physically and chemically to be absorbed in the body. The digestive anatomy of an animal can highly influence how much or little of a food nutrient is utilized. In this blog post I will briefly explain the way in which the bodies of the Tasmanian devil and the honey possum digest the food they consume. The process of digestion will begin with the food entering the animal’s mouth and move all the way through the body, until defecation.
Dentition
The dentition of both of these species is varies greatly. The Tasmanian devil has a full mouth of teeth including long upper incisors, short and heavy canines, and triangular shaped molars (10). These teeth are specially designed for breaking through tough skin and bones. The purpose for the honey possum dentition is very different. It has two front teeth on the lower jaw while the other teeth are all greatly reduced (7). This forms a keel-like structure, purposed to support the tongue as it moves in and out of the mouth (7). The evolutionary adaptation to the snout of this animal has become very elongated, a clear advantage to getting in close to a flower to obtain the nectar. It follows the same idea as the hummingbird with its elongated beak. A very useful adaptation also occurs with the honey possums tongue, as it has become very long to reach those spaces in the flower where the nectar is held (7). It also has many papillae surfacing the tongue to help collect pollen which is then scraped off by a series of combs on the roof of the mouth (7).
Now, how the food travels in the bodies of these two animals. The Tasmanian devil gorges itself where the food is passed from the mouth down the esophagus and into the stomach. This stomach is very simple as it does not have diverticula or a fore stomach (21). The stomach has a very low pH and is lined with glandular mucosal cells (21). This physiology of the Tasmanian devil is very different from the honey possum. The honey possum has a diverticulum of the stomach where nectar/pollen is passed through first and then into the main chamber of the stomach, which is bi-lobed (7). The honey possum does not have Chief cells in its stomach and therefore does not secrete peptidases which work to breakdown proteins (22). There are no reports of pH measurements throughout the gut.
In the Tasmanian devil, the food moves from the stomach into the small intestine where most of nutrients are absorbed. The small intestine is very short and contains an alkaline fluid. The small intestine contains the duodenum, jejunum and ileum, in that order (21). This is exactly the same for the honey possum (7).
The Tasmanian devils food is then moved from the ileum into the, very small, caecum where some fermentation occurs and continues on into the colon where water and electrolyte absorption occurs (21). The remaining food material that is undigested is moved out of the body through the rectum and then the anus. This differs slightly in the honey possum as they do not possess a caecum, as they do not need to ferment their food like other animals (22). Instead pollen is passed from the ileum into the colon where much less absorption occurs. The excretion of the pollen is the same as the Tasmanian devil.
When given a marker to test transit time for pollen in the honey possum, it first appears around 2-4 hours but averages to six hours (7). For the Tasmanian devil the marker first appears around 3-4 hours and averages around 7 hours (21). So while these two animals live in different areas and eat very different foods they display many similarities.