From an anatomical point of view, the
domestic koi is a carp with a few modifictions brought about by
modern day breeders. Of course, with all the changes and
modifications to the Koi of today, general anatomy is obviously
the same but shape and proportion will depend on variety.
Understanding the anatomy of a Koi may assist you in the general
health and treatment of your fish. Below is a diagram of the
Koi's anatomy with descrptions of the koi's Anatomy and
Physiology.
| 1 |
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. |
| 2 |
Nostrils |
The nostrils are just
forward and slightly above the eyes. The nostrils are
used purely for scent. |
| 3 |
Barbel |
The barbels located are
located on the upper lip of the koi and contain many
sense receptors to help locate food. |
| 4 |
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. |
| 5 |
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. |
| 6 |
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. |
| 7 |
Gall Bladder |
Located just below the
liver, the Gall Bladder stores bile and releases it to
help with digestion. |
| 8 |
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. |
| 9 |
Spleen |
The spleen produces lymph
cells (a yellow fuild consisting mostly of blood plasma
and white blood ceels) and stores red blood cells. |
| 10 |
Intestines |
See Digestive System for
further details. |
| 11 |
Repoductive 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. |
| 12 |
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. |
| 13 |
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. |
| 14 |
Anal Fin |
The anal fin located just
forward of the tail and is primary for stabilization. |
| 15 |
Caudal or Tail |
The caudal (tail) acts as
the koi's rudder and can be used to gain maximum speed /
thrust. |
| 16 |
Kidney |
. |
| 17 |
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. |
| 18 |
Dorsal Fin |
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. |
| 19 |
Stomach |
See Digestive System for
further details. |
| 20 |
Pyloric Caeca |
. |
| 21 |
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. |
| 22 |
Scales |
. |
| 23 |
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. |
| 24 |
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. |
| 25 |
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. |
| 26 |
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. |
| 27 |
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. |
| 28 |
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. |
