Digestive Anatomy
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The North American River Otter has a relatively standard Mammalian Carnivore digestive system. Carnivores have a simple and short digestive system as they don't need be as efficient at extracting nutrients from their food as herbivores or omnivores which will already have done the extraction for the river otters when they are consumed as their prey (White et al. 2007)
The components:
The components:
- Headgut (mouth and pharynx) : This area is very important to the sea otter as the teeth are essential for trapping and consuming their prey. Fish are slippery and quick, the river otter has 1 upper and 1 lower "carnassial" or canine teeth that are good for gripping and shearing, 3 incisors and wide molars for crunching. The river otter consumes its entire prey bones and all making these necessary (Kruuk 1995)
- Foregut (esophagus and stomach): esophagus has an inner layer of circular muscle and an outer layer of longitudinal muscle, and the stomach is a single compartment with a stratified squamous epithelium layer and has pyloric granular and proper gastric muscosa to maintain the acidic nature of the stomach due by secrete HCL and bicarbonate (Reed-Smith 2012)
- Midgut/ Hindgut (digestion and absorption site): river otters have a unilateral digestive system, consistent with other carnivores and a short alimentary canal. the intestines are lined with a mucoid substance that protects the otter from sharp objects (example bones of fish), Reed-Smith 2012
- Accessory Organs (aid in digestion and absorption): Pancreas (alpha-amylase production, lipase production), Liver (hormonal control, bile secretion), Salivary Glands (alpha-amylase, lipase) (Finegan and Stevens 2008).
Digestion in River Otters
Based on information from: White et al. 2007 and Finegan and Stevens 2008
1. Begins with consumption of prey (primarily fish, also insects, crustaceans, amphibians, reptiles, birds, mammals)
2. in the mouth there is mastication of the food, and the use of the tongue and muscles in the mouth, along with preliminary salivary digestion, followed by deglutination, and the cessation of voluntary control
3. Peristaltic contractions in the esophagus carry the food towards the stomach in a unilateral (one direction) manner.
4. The food then passes through a pyloric valve or sphincter into the stomach, first site of digesta retention, where the food is subject to chemical (acidic stomach) and mechanical digestion (contractions of the circular, longitudinal and oblique muscle layers), here bones and other indigestible materials may reside for a few weeks and experience minute calcium extraction.
5. The simple-stomach of this vertebrate digests and moves food through the GI tract by electrical stimulation from an axial pacemaker that initiates circular muscle contraction followed by peristaltic waves and periodic emptying into the small intestine with sphincter relaxation
6. Once the food enters the small intestine of the otter, it begins the main absorption process including carbohydrate, lipid and protein digestion. In a carnivorous diet protein digestion and utilization is more efficient than carbohydrate.
7. In the hindgut, there is water and electrolyte resorption and excretion through the anus. The river otter primarily excretes fish bones, scales, and other indigestible items, but has highly variable excretion patterns making analysis difficult at times (White 2007).
1. Begins with consumption of prey (primarily fish, also insects, crustaceans, amphibians, reptiles, birds, mammals)
2. in the mouth there is mastication of the food, and the use of the tongue and muscles in the mouth, along with preliminary salivary digestion, followed by deglutination, and the cessation of voluntary control
3. Peristaltic contractions in the esophagus carry the food towards the stomach in a unilateral (one direction) manner.
4. The food then passes through a pyloric valve or sphincter into the stomach, first site of digesta retention, where the food is subject to chemical (acidic stomach) and mechanical digestion (contractions of the circular, longitudinal and oblique muscle layers), here bones and other indigestible materials may reside for a few weeks and experience minute calcium extraction.
5. The simple-stomach of this vertebrate digests and moves food through the GI tract by electrical stimulation from an axial pacemaker that initiates circular muscle contraction followed by peristaltic waves and periodic emptying into the small intestine with sphincter relaxation
6. Once the food enters the small intestine of the otter, it begins the main absorption process including carbohydrate, lipid and protein digestion. In a carnivorous diet protein digestion and utilization is more efficient than carbohydrate.
7. In the hindgut, there is water and electrolyte resorption and excretion through the anus. The river otter primarily excretes fish bones, scales, and other indigestible items, but has highly variable excretion patterns making analysis difficult at times (White 2007).
Metabolism
The river otters have a very rapid digestion and fast metabolism. On average the food consumed by a river otter passes through their digestive tract in 1 to 4 hours and have a shorter digestive tract than most carnivores (Henry et al 2012). Otters spend about 60% of their day active, foraging/ hunting for food, playing, swimming, diving etc, and need to consume enough food for basal requirements as well as active (additional metabolic changes occur during growth, reproduction, and thermoregulation). In addition musteldiae species and semi aquatic species have high metabolic rates due to their physiology and activity levels, and there is an increased rate of food passage through the digestive tract with increased activity, with a normal average rate or 202mins when fed a balanced protein rich diet (White et al. 2007). Since energy requirements is based on metabolic rate, the river otter should be consuming up to 20% of their daily average body weight in order to maintain the appropriate nutrient requirements for growth, maintenance and reproduction, these values are varied depending on subspecies of otter and contributing abiotic and biotic factors (Reed-Smith 2012).
**See Energy Requirements in contents for detailed information and calculations
**See Energy Requirements in contents for detailed information and calculations
*** References for this page:
1. Finegan, E. and Stevens, E. (2008). The digestive system of vertebrates website. Comparitive Nutrition Society. Website. http://www.cnsweb.org/extra/digestvertebrates/AAAEdStevensINTRODUCTION.html [1, March 2014].
2. Henry, B., Maslanka, M., Heuer, K., Reed-Smith, J., and Nidasio, G. (2012) Otters in zoo, aquaria, rehabilitation and wildlife sanctuaries. IUCN River Otter Specialist. Available: http://www.otterspecialistgroup.org/Library/TaskForces/OCT.html [March 2, 2014].
3. Pfeiffer, P., & Culik, B.M. (1998) Energy metabolism of under- water swimming in river otters (Lutra lutra L.). J. Comp. Physiol. 168B: 143–148
4. Reed-Smith,J . (2012). North american river otter. Husbandry Notebook, Edition 4. (Chapters 1-6).
5. White, S.C., Clark, D.W., Day, C.D., Sikes, R.S. (2007) Variation in digestive efficiency of captive north american river otters (Lontra Canadensis) on various diets. Zoo Biology. 26: 41-50.
1. Finegan, E. and Stevens, E. (2008). The digestive system of vertebrates website. Comparitive Nutrition Society. Website. http://www.cnsweb.org/extra/digestvertebrates/AAAEdStevensINTRODUCTION.html [1, March 2014].
2. Henry, B., Maslanka, M., Heuer, K., Reed-Smith, J., and Nidasio, G. (2012) Otters in zoo, aquaria, rehabilitation and wildlife sanctuaries. IUCN River Otter Specialist. Available: http://www.otterspecialistgroup.org/Library/TaskForces/OCT.html [March 2, 2014].
3. Pfeiffer, P., & Culik, B.M. (1998) Energy metabolism of under- water swimming in river otters (Lutra lutra L.). J. Comp. Physiol. 168B: 143–148
4. Reed-Smith,J . (2012). North american river otter. Husbandry Notebook, Edition 4. (Chapters 1-6).
5. White, S.C., Clark, D.W., Day, C.D., Sikes, R.S. (2007) Variation in digestive efficiency of captive north american river otters (Lontra Canadensis) on various diets. Zoo Biology. 26: 41-50.