Skin, Kiwa, Sashi, and Fukurin by Masaki Okamoto

Skin
The following kinds of skin (shimpi) can be found on scaled Koi: Surface or upper skin (hyousou shimpi) There are two types of surface or upper skin. The first type is located on the outer top surface of the scale of the Koi. This skin is only on the exposed portion of the scale. Hi (red), sumi (black), and shiro (white) pigment cells are easily formed in this part of the skin. The second type of surface skin is skin that has grown from between the scales and emerged on the surface or body table as it is sometimes referred to. It is believed that the pigment cells thrive more readily in the exposed portions of the skin because there is a relative abundance of oxygen. Conversely, there are fewer pigment cells in the skin under the scales. The black pigment, melanin, on the scales forms sumi. The exception is the black-blue color seen on Asagi. Here there are no pigment cells on the scales. Rather, the color is seen through the scales. Only Asagi has this special coloring. Middle layer of skin (nanshitsu shimpi) This skin exists between the scales and wraps a portion of the scale. This skin is thin and sturdy and has considerable elasticity. It is soft skin and is called nanshitsu shimpi (middle layer skin). Pigment cells usually exist in this layer of skin as well as in the upper skin. Lower layer skin This is the skin, which exists below the scales, between the scales and the muscle tissue. Pigment cells are found in this layer as well. Black cells and yellow-red cells can be found in this portion of the skin. Optical cells also exist in the lower skin. When pigment does exist, it is mostly black and optical cells. The resulting color is blurred and not solid. Pigment cells can and do exist in the tissue underlying the skin. This is especially true of Asagi. However in other varieties, pigmentation in this underlying tissue is scarce or nonexistent.

Kiwa
Kiwa is the back (toward the tail) and side edges of the hi (red) pattern. There are various types of kiwa and it is considered to be as good as the edge of the pattern is sharp. The sharper the demarcation line between the colors the better. It is desirable that the scale has a concentration of color at its edge. If the pattern is sumi (black) instead of hi (red), the back and side edges of the pattern are referred to as sumi kiwa or sumi giwa.

• Kamisori Kiwa which cuts across the scales without following the edges of the scales, is called kamisori kiwa. This type of kiwa is seen in the top portion of Fig. 2. In small Koi, this type of kiwa is displayed as color (hi or sumi) on part of the scale and no color on the other portion of the scale.

• Maruzome In maruzome kiwa, the dividing line between the white and the hi or the sumi follows the edges of the scales in a scalloped pattern. This type of kiwa is seen in the lower portion of Fig. 2. Only the hi pigment cells can be seen on the scale. The middle layer of skin is not visible. Hi pigment cells are also present in the middle layer skin under the red scales. This means the hi has several layers and is thick. The white scales can also exhibit a maruzomi type of pattern.

• Konzai There exists a type of kiwa, which is a blend of kamisori and maruzome. Many Koi have this mixture, called Konzai, and examples of this type of kiwa are plentiful.

Sashi
When sashi exists, it means that pigment cells exist in the middle layer skin. It is generally believed that hi is stable on Koi with sashi. Sumi can also have sashi.

• Sashi of hi Sashi of hi only exists when hi pigment cells are present in the middle layer shimpi. These hi pigment cells can often be seen through the white scales on the leading or forward edge of the hi pattern. If the sashi extends beyond about one scale or is uneven, the hi pigment of the middle layer skin is thought to be unsettled and its concentration is undesirable. If the white does become so thick that the sashi cannot be seen, the white is referred to as finished. Small Koi with good white ground but white ground that isn't thick are favored in Japan. Red pigment cell distribution
  There is a type of red pigment, which exists only on the surface of the scale. A second type of red pigment exists in the middle-skin as well as on the surface of the scales. Of the two, it is widely believed that the second type is more desirable. It is the type that produces sashi and is thought to be more stable for the long term. The first type on the other hand, is thought to be less reliable and has the possibility of disappearing. To distinguish the different types look for sashi. Only the second type has sashi. However, Sensuke hi, which doesn't have sashi, is the second type. To judge whether or not there is pigment in the middle skin, carefully bend the Koi into a U shape. A whitish gap will appear if there is no red pigment in the middle skin. The nature of the white pigment cells is less well known. The process of how the white pigment is derived is also unclear. There seems to be no definite pattern to how this color develops. There have been cases in which Koi have grown large even after having their white ground finished at a small size.

• Sashi of sumi Sashi of sumi can sometimes be seen when sumi exists directly behind or within the hi pattern. Such an appearance denotes no problem with the sumi but does denote a problem with the hi thickness. When sumi exists within the hi pattern, it is called kasanesumi. Kasanesumi is judged to be acceptable if it is a clear, continuous block of color. The thickness of the hi may be determined by observing the sashi of the sumi. Sashi may also be seen when sumi is inserted under the shiro (white) ground and the shiro is not thick.

Fukurin
Fukurin is a beautiful combination of skin and scales. It appears at the edges of the scales and is easily missed if one is not observant. It occurs in two forms, which are referred to for purposes of this article as Type 1 and Type 2. Good fukurin is prized in Japan where high grade Koi are revered as living art. It is all but impossible to see fukurin on small fish and can be subtle and easily missed even on larger fish if one is not specifically looking for it, especially Type 2. Fukurin is easier to see on fish older than three years and larger than 60 cm.

• Type 1 fukurin Type 1 fukurin exists when the middle layer shimpi grows out onto the surface of the adjacent scales to become the upper skin. Visible on the outer surface of the fish is scales surrounded by skin (Figure 3 & 4). Because the skin and the scales are usually slightly to substantially different color or shade, the skin often gives the scales a reticulated appearance, netting or edged effect. This is also because the skin and the scales reflect light differently. Many Koi exist with this type of fukurin. Examples are Ogon, Asagi, Kujaku, and Matsuba. All these varieties exhibit type 1 fukurin. (Figures 3 and 4) Also, type 1 fukurin can appear on Kohaku, Sanke (particularly Matsunosuke line Sanke) and Showa in big Koi. (See Figure 5) Note that the shine on the white scales shown in Figure 5 is not fukurin. Fukurin is the skin, which can be seen surrounding those scales. (Editors note: There is some speculation that the shine is a rudimentary form of Hiroshima Gin Rin.) Fukurin is difficult to see in small Koi particularly on the Gosanke (Kohaku, Sanke, and Showa). As these Koi become larger, the middle layer skin (nanshitsu shimpi) can grow and extend out to the surface of the fish. These Koi are few in number and are not often seen. If one learns to see this middle layer skin as it grows from between the scales onto the exterior surface, one learns to see fukurin. Fukurin is most easily seen on the white ground and is type 1.

• Type 2 fukurin A second type of fukurin is formed when the upper skin grows past the edge of the scale it originates on and overlaps the upper skin on the scales behind or to the side of it. This type of fukurin is rare and when good specimens are found, they are highly valued. To observe type 2 fukurin, look closely at the tip of the scales. Specifically, observe the tip or edge of the scales in the white ground. If the soft skin grows onto the next scale, this is type 2 fukurin. (Figures 6 & 7)