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Koi Anatomy

Cyprinus carpio ( Common Carp ) is a large, soft-finned freshwater fish that has through centuries of cross-breeding and in-breeding of mutations, become our beloved koi ( Goi) . Koi have an elegant simplicity of shape and healthy ones are fitted out with a physical structure and organs that are admirably suited to their waterey way of life.

The length of a koi, as used by a hobbyist, is the measurement from the tip of the nose to the end of the tail which determines the total length. Length is the most commonly used measurement  to which there are expected increments at certain ages it is the major factor in pricing and purchasing, and it determines size categories at shows.

Koi have been bred to have less body depth than natural carp. Depth is not as noticeable as length because of the swimming position. It is not critical as long as the fish is generally in proportion, although females usually have more depth than males, especially when laden with eggs. The following quick reference table simplifies each organ of the kois anatomy for ease of use. Followed by a more comprehensive section on what should be looked at when viewing your fish or looking to buy in new stock.

koi anatomy descriptions guide

Thu, 06/24/2010 - 14:38 by Splashtastic   Tags:

koi anatomy

 Eyes  The eyes are just forward of the gills. Koi can see in two directions at same time - to either side of the body as well as above or below on each side.
 Nostrils 
 The nostrils are just forward and slightly above the eyes. The nostrils are used purely for scent.
 Barbel
 The barbels located are located on the upper lip of the koi and contain many sense receptors to help locate food.
 Gills  Gills have a similar function to the lungs. The gills are served by a series of fine blood vessels. As the water passes over the gills, oxygen is absortbed through the blood vessels and then transported directly to the body. Carbon Dioxide is return to the water via the gills.
 Fin (Pectorial)  The pectorial fins are paired and located on the lower sides of the koi. They can be used to rotate the koi almost on the same axis, this is done by one fin working in the other direction to the other. The also act as the main braking fins, they achived this by placing the fins out to provide a large surface area to the water. They also use them when looking for food to stir up the bottom.
 Fin (Pelvic)
  The pelvic or ventral fins are paired and located on the lower sides of the koi approx mid body. The pelvic fins enable the koi tp rise or descend as it swims, you could say they act as hydrofoils.
 Fin ( Anal)
  The anal fin located just forward of the tail and is primary for stabilization.
 Fin (Caudal or Tail)
  The caudal (tail) acts as the koi's rudder and can be used to gain maximum speed / thrust.
 Fin ( Dorsal)
  The dorsal fin located on the top of the koi is the major stabilizing fin. It works in a similar fashion to a keel on a ship by keeping the koi upright. Koi can lower the dorsal fin to create a more streamlined effect when the koi needs to move at faster speeds.
 Mouth  The mouth of Koi are located in an inferior position - not quite at the tip of the head but slightly below. This indicates that it has bottom feeding habits.
 Lateral Line
  The lateral line runs roughly along the mid-body of the koi. The lateral line is a row of special pores that open into a channel which runs to the head and brain of the koi. The channel is filled with a viscous solution which is extremly sensitive to vibrations in the water.
 Swim Bladder
  The swimbladder, located just below the backbone consists of 2 different size chambers. Fish adjust their position by inflating or deflating these chambers, this changes the density relative to the surrounding water. In conjunction with the auditory system it controls the fishes orientation, level at which they swim etc.
 Ears  Fish have internal ears that repsond to vibrations within the water. The auditory canal is connected to swin bladder and is used for balance.
 Liver  The liver helps remove waste from the blood and controls the use of digested food. It also produces bile which is used in the digestion / absorption of fat.
 Gall Bladder
  Located just below the liver, the Gall Bladder stores bile and releases it to help with digestion.
 Spleen  The spleen produces lymph cells (a yellow fuild consisting mostly of blood plasma and white blood ceels) and stores red blood cells.
 Reproductive Organs
  The internal sex organs of the male are the testes and the ovaries of the female. In both the male and female they are located below the swimbladder. Eggs and sperm exit the boby via the gonopores which is located just in front of the urinary opening. The gonopores are connect by the gonoduct.
 Anal Pore
  The anal pore is located just forward of the anal fin. The waste products of the koi's digestive system are expelled via the anal pore. Water in the form of urine is also expelled via the anal pore.
 Urinary Bladder
  The urinary bladder plays an important part for the koi. As the salt content of the koi is higher then that of the water in which it lives the koi's body is continually taking in water which tries to equalize the salt concentation, this is known as osmosis. As a result of this process the koi must release the excess water, otherwise it would blow up like a balloon.
 Digestive System
  The digestive system of koi is more or less like that of any higher animals but differs from many as the koi doesn't have a stomach as such. Food enters via the mouth and is crudly crushed by the pharyngeal teeth (bony projections from the gill supports). From there it passed into esophagus and then into the intestines. The anterior part of the in intestines are swollen and look a lot like a stomach. The intestines long and coiled, usually 4-5 times the length of the koi. The is due to the fact the the vegetable matter eaten by the koi require more time within the body to be broken down so that the goodness is released. The intestines exit the body at the anal pore.
 Nervous System
  The nervous system of a koi consists of optic and other sensory nerves that radiate from the head. Fine fibers at the nerve endings transmit and receive message to the koi's brain, which is relatively simple. The koi's spinal cord helps protect the central nervous system which extends to all parts of the boby.
 Mucus Layer
  The mucus layer covers the entire external area of the koi. The mucus layer provides protection for bacteria and fungus and gives the koi there slippery feel. It is therefore important that you hands are wet before handing koi, to ensure that the mucus layer is not damaged.
 Colour  The colour variations in koi is determined by the amount of guanin cells (reflective tissue) in the skin below the scales (dermis). The guanin cells contain waste by-products of the bodies metabolism. The outlayer (epidermis) cells contain colour pigments, these are Erythrophores (contain red or orange pigment granules), Melanophores (contain the black pigment melanin), Xyanthophores (contain yellow pigment granules). Their placement in the skin will determine the colour of a koi. The more complete the guanin cell layer, the more metalic the apperance of the koi as and if this layer is partially or completly missing more colour are visable deeper.

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Comprehensive koi anatomy Guide

Thu, 06/24/2010 - 14:36 by Splashtastic   Tags:

When looking at the body vertically, there are three basic divisions, The head region, trunk region, and caudal region. Horizontally, the upper portion is the dorsal area, and below the lateral line the body is called the ventral area. The lateral line is present in all fish. It is difficult to see it on a fully scaled fish, but is quite evident on a kawa (leather) koi. The lateral line is a richly endowed receptor of energy waves created in water medium by sound and motion. Koi quickly discern the frequencies produced by their master's voice (or any sound used to call them to food). The lateral line is very sensitive, even to minor variations, and loud noises institute immediate protective/evasive action. Although koi have no ears per se their "hearing" is exceptionally keen. They have a wider range (especially in the lower range) than most fish.

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