The digestive system of koi is interesting in that they seem to lack a true stomach. Due to this they are not able to store a meal, this is why you are often told to feed Koi smaller meals two to three times per day, rather than one large meal. Koi have a very long intestine, which is around five times the length of the body. They also have a pancreas and gall bladder. In summer when the temperture are high, koi digest and absorb food quickly. In warmer temperatures you will notice your koi love eating often. In winter as the water temperature lowers koi reduce the amount of food they consume. Koi use up oxygen when digesting food and need a good source of oxygen in the pond at all times. There are different varieties of koi food available for the different seasons. In summer it is good to feed your koi a growth food with a good percentage of protein and in winter to switch to a winter food or Wheatgerm food, which is easier for the koi to digest.
The Koi’s urinary system. The kidneys are paired organs, blood is filtered and excessive water and metabolic wastes form urine, which is then excreted out of the koi via a urethra in the anal pore. The Koi’s nervous system consists of a brain, spinal cod and peripheral nerves. The autonomic part of the nervous system controls vital functions such as the heart, respiration and blood pressure. Koi have good sense organs that help with finding and detecting food. Sight is also important to detect predators and their surroundings and koi are able to see in colour.
The respiratory system of koi consists of a mouth and gills. Koi draw water in through the mouth then it flows into the two opercular cavities, which house the gill archers and a complicated system of capillaries and blood vessels.
Gills do not only help with breathing they also excrete waste products, which build up in the blood e.g. ammonia and larger compounds like purines.
The life span of a koi is around 40-50 years, however there are many reported cases where they are much older. When you go to a koi shop to buy a koi remember it may live as long as you will and look after it with the best filtration system and good high quality koi food.
Part 1 of this article can be found here.