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The Dojo Loach

By: Neil Hinckley
 
Common Name: Dojo Loach

A Gold Dojo Loach © Neil Hinckley
Latin Name: Misgurnus anguillicaudatus
Origin: Japan and China
Temperature: 60-77ºF (16-25ºC)
Ease Of Keeping: Very easy
Aggressivness: Non-aggressive
Lighting: Dim to bright.
Adult Size: Up to about 10" with 8" being somewhat typical.
Minimum Tank Size: 30 Gallon
Feeding: Will eat most things, but prefers sinking foods.
Spawning Method: See below.
 
Comments: The dojo loach has often been described as the perfect beginners fish because of its extreme hardiness. It can withstand high ammonia with no problem, and even if one does escape from your tank, it is likely to live up to a few days without any serious problems outside of the tank.
 
Another name for the Dojo loach is Weather loach or Weather fish. It got this name from its tendency to become very active just before a storm hits. It is often thought that this is because of a sensitivity to changes in barimetric pressure.
 
There are a couple different varieties of Dojo loach available commertially. There is the wild type, and the gold. The wild type is usually a dark brown with spots. Sometimes they are very thick bodied, and sometimes quite thin. These seem to be genetic traits and not have much to do with the actuall health of the fish. The gold variety is a pale yellow to rich orange color, but is not albino. In the specimines that I have seen, they also have spots, though they are generally not very noticable. I have never come across a thick bodied gold dojo, although they may exist.
 
The dojo loach also has a lot of personallity. Many owners talk about how their dojo's seem to like to be handled, and I have to agree here. My two gold dojo's would often swim through my fingers, or sit in my hand when I was cleaning the tank. I also loved to hand feed them. They love shrimp pellets, freeze dried tubifex worms, and sinking tropical pellets.
 
Dojo loaches do not commonly breed in the aquarium, but there have been instances where it has happened. For one specific case, see Dojo Loach Spawning Experience at Loaches.com.
 
Below is a somewhat technical overview of these amazing fish.

How the adaptations and peculiarities of Misgurnus anguillicaudatus make it successful

By: Neil Hinckley
 
In the aquarium hobby, there are a few different types of fish. There are the experts' fish that require diligent looking after in order to have them survive in captivity. There are the vast majority of fish that need to be looked after and cared for constantly. These are delicate in their own ways, but are more adaptable and forgiving. Then there are those fish that you can't kill. One of these hardy fish is commonly known as either the Dojo or Weather loach. It's natural environment is in temporary ponds and streams in Japan and China and so it has needed ways to survive in stagnant water and even outside of water for some time. This paper will discuss how the adaptations caused by it's environment have benefited the modern Dojo loach in it's changing environment and how these same adaptations make it a desirable commercial fish.
 
Low dissolved oxygen is a problem in many aquatic environments, including stagnant water. One way that many fish have evolved to cope with this lack of oxygen is that they have developed certain organs to be able to use atmospheric air. In the case of Misgurnus anquillicaudatus, it has developed a modified intestinal tract in order to enable it to breath air. Eventually this adaptation became so useful that the Dojo loach could survive solely on atmospheric air if needed. This means that it can survive in many very harsh aquatic environments where other fish would die from lack of oxygen simply by ingesting atmospheric air.
 
Being able to use atmospheric air so effectively probably led to a lot of the other adaptations that makes the Dojo loach so hardy. The most important of these adaptations is Misgurnus anquillicaudatus's ability to cope with high levels of endogenous (internally produced) ammonia. Fish produce ammonia when Catabolise (break apart) amino acids and adenylate (a product of adenosine and phosphoric acid). When they are in an aquatic environment fish are constantly releasing excess ammonia into the surrounding water through their brachial epithelia (i.e. gills) and cutaneous surfaces (skin). However, once the fish is removed from it's liquid enviroment this method is no longer practical. There are six major ways that air breathing fish have adapted to the ammonia buildup that occures when they are out of the water for extended periods of time. These are:
  1. Suppressing amino acid catabolism.
  2. Partial amino acid catabolism (leading to a build up of alanine).
  3. Glutamine synthesis
  4. Conversion of ammonia to urea.
  5. Altering the PH of the body surface to increase ammonia volatilization .
  6. Developing a high tolerance for ammonia in the body.
Out of these six possibilities, Misgurnus anquillicaudatus uses five of them, only leaving out number (4). The reason that the Dojo loach uses so many different mechanisms to deal with ammonia build up is that it uses different techniques for different time periods of activity on land. During the first 24 hours out of water, Misgurnus anquillicaudatus uses primarily techniques 1, 2, and 3 in order to control ammonia build up. However, after the first day of aerial exposure it depends on 1, 5, and 6 in order to survive.
 
The reason for using different techniques during different time periods is likely two fold. The first part being that in the first 24 hours of aerial exposure, the loach is most often looking for soft mud in which it can burrow in order to keep from drying out during a drought. This requires that the loach be active during this time period in order to move on land and burrow into the mud. The easiest way for the loach to do this and still accumulate little ammonia is to only partially catabolise amino acids. After it has found a safe place to wait for water, this strategy no longer makes sense. The loach will move very little once it has established itself in a pocket of mud, and so it is no longer practical to use such an energy intensive method of reducing ammonia, and so the loach changes to a more passive method of eliminating ammonia. It first builds up large amounts of ammonia in the blood and bodily tissues, with concentrations in the blood reaching as much as 5.02µmol/ml (about 80ppm6). This buildup demands that the Dojo loach be very tolerant of ammonia (method 6) as most aquarium fish have difficulty handling 5-10ppm in their water, and mammals typically can not live with 32ppm in their bodies5. Once the ammonia has built up to near these levels the loach can begin to use method 5. In order to make ammonia volatilization a practical method to controlling the amount of ammonia present in it’s body, Misgurnus anquillicaudatus has to increase the rate at which the ammonia leaves its body. The way that it does this is by increasing the PH of it’s body. As the PH of a medium goes up, it holds less and less ammonia, so by increasing the PH of it’s body the loach can maintain a high, but tolerable ammonia level.
 
All of these adaptations are what has made Misgurnus anquillicaudatus successful in it’s natural environment, but they have had the added benefit of making the loach very successful as its environment is changed from a natural one into a man induced environment. One of the major crops in its native range is rice, and rice is often grown in large patties, or fields full of water. This is where the loach as become particularly successful. These patties are full of low oxygen content stagnant water, and are often fertilized with ammonia fertilizers. Needless to say this is not a favorable environment for most fish, but the Dojo loaches ability to use atmospheric air and its high tolerance to ammonia allow it to thrive in these large manmade marshes.
 
In the aquarium market, there are a few reasons why a fish might be popular, and therefore practical commercially, with aquarists. It can be beautiful, with bright colors, interesting patterns, or ornamental shapes. It can be unusual, or even odd in shape or color. It can fill a niche, such as algae eaters, or it can be hardy. An obvious choice for a hardy fish is the dojo loach. It practically eliminates the effects of any mistakes the beginning aquarist could make, and has been recognized throughout the market for it. Of course, the market has a tendency to try and improve on good things, and so it has been breeding and selling a color morph of Misgurnus anquillicaudatus called ‘Gold Dojo loaches’ for years in order to provide a more attractive fish to the aquarist. Aside from being hardy and beautiful, the Dojo also has some other endearing traits that make it popular. It is sensitive to changes in atmospheric pressure, and so will often become extremely active as much as two days before a storm hits. This is how it has come to be labeled as the Weather loach in some instances. It also is an odd shaped fish, being almost eel shaped, which also adds to its lure to the new fish keeper.
 
One other point of interest is that there has been a strain of Misgurnus anguillicaudatus found in Memanbetsu, Hokkaido, Japan that exhibits a trait that is typically associated with the live bearing fish Poecilia formosa, that of gynogenesis. Gynogenesis is also referred to as sperm-dependent parthenogenesis. What this means is that a female of the species produces eggs that do not need to be fertilized by sperm in order to develop, but the presence of sperm in needed in order for the eggs to start to develop. This also means that in order to produce viable fry (offspring) a male of the same species is not needed. In fact, it has been shown that goldfish sperm will induce development of the eggs, and results in a good number of viable fry.
 
All of these adaptations and traits have allowed Misgurnus anquillicaudatus to become one of nature’s success stories, an animal that continues to survive regardless of the changes in its environment. And not only is it successful in nature and the new environment that man created, but it is also successful in mans home as a pet.
 
Bibliography
 
1. Allozyme variation and genetic differentiation in the loach Misgurnus anguillicaudatus. By: KHAN, M; ARAI, K. Fisheries Science, Apr2000, Vol. 66 Issue 2, p211
 
2. Structure and mucous histochemistry of the intestinal respiratory tract of the mud loach, Misgurnus anguillicaudatus (Cantor). By: Park, J. Y.; Kim, I. S.; Kim, S. Y.. Journal of Applied Ichthyology, Aug2003, Vol. 19 Issue 4, p215
 
3. A Cryptic Clonal Line of the Loach Misgurnus anguillicaudatus (Teleostei: Cobitidae) Evidenced by Induced Gynogenesis, Interspecific Hybridization, Microsatellite Genotyping and Multilocus DNA Fingerprinting. By: Morishima, Kagayaki; Horie, Shin; Yamaha, Etsuro; Arai, Katsutoshi. Zoological Science, May2002, Vol. 19 Issue 5, p565
 
4. The Loach Misgurnus anguillicaudatus Reduces Amino Acid Catabolism and Accumulates Alanine and Glutamine during Aerial Exposure. By: Chew, Shit F.; Yi Jin; Ip, Yuen K.. Physiological & Biochemical Zoology, Mar/Apr2001, Vol. 74 Issue 2, p226
 
5. Five tropical air-breathing fishes, six different strategies to defend against ammonia toxicity on land. (eng; includes abstract) By Ip YK, Physiol Biochem Zool, 2004 Sep-Oct; Vol. 77 (5), pp. 768-82; PMID: 15547795
 
6. A Cryptic Clonal Line of the Loach Misgurnus anguillicaudatus (Teleostei: Cobitidae) Evidenced by Induced Gynogenesis, Interspecific Hybridization, Microsatellite Genotyping and Multilocus DNA Fingerprinting. By: Morishima, Kagayaki; Horie, Shin; Yamaha, Etsuro; Arai, Katsutoshi. Zoological Science, May2002, Vol. 19 Issue 5, p565, 11p, 5 charts, 4 graphs, 1 map, 2bw
 
Other References
 
7. 5.09µm/ml4,5= .00000509mol/g= .00000509mol/(1/16mol)= 8.144x10-5/1= .00008144/1= 81.44/1,000,000mol = 81.44ppm
 
* Assuming that blood and water have the same density.
 


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