Pond loach

Thepond loach(Misgurnus anguillicaudatus), also known as theDojo loach,oriental weatherloachororiental weatherfish,is afreshwater fishin theloachfamilyCobitidae.  They are native toEast Asia, but are also popular as anaquarium fishand introduced elsewhere inAsiaand toEurope,AmericaandAustralia.The alternate nameweather loachis shared with several otherCobitidae, including the other members of the genusMisgurnusand the spotted weather loach (Cobitis taenia, commonly known as spined loach). This term comes from their ability to detect changes inbarometric pressurebefore astormand react with frantic swimming or standing on end.
Wild pond loaches can grow up to 12 in (30 cm) long, but may only reach a length of 6 in (15 cm) in captivity.They also come in a variety of colors, such as pink, orange, albino and gray, and can vary in colour from yellow to olive green, to a common light brown or grey with lighter undersides. Like many other loaches, pond loaches have slender,eel-like body. The mouth of the loach is surrounded by three sets ofbarbels, which are used to sift throughsiltorpebblesto find food, and also to dig under gravel and sand to conceal the fish out of nervousness or self-defence, unlike the other loaches who use the spines beneath the eyes.
Pond loaches arebottom-dwellingomnivores, feeding mainly onalgaeorscavengingorganic materials, and may also eat ontubifex wormsand other small aquaticinvertebrates.
Pond loaches are very hardy fish that can live in poor-quality water, and can survive short periods ofdroughtby producing a layer of moisture-trappingmucusto keep themselves damp. Despite their resiliance against water conditions, pond loaches should still be kept in pristine water to ensure their health and prosperity within the home aquarium or pond. These loaches prefer a soft, sandy, smooth stone, fine gravel substrate, or bare bottomed tank as opposed to any form of rocks or rough gravel, which have been known to damage the sensitive barbels and skin.
Unlike most other fishes, the pond loach can burrow into and hide in soft substrates, breathe atmospheric air throughenteral respirationif necessary, and survive for long periods of time outside of the water.For the pond loach to survive on land for extended periods of time, it has physiological adaptations to reduce toxicammoniaconcentrations in the body and maintain homeostasis and normal functioning of tissues. When on land, the pond loach can suppress protein breakdown and catabolism (which avoids creating ammonia), switch to partial amino catabolism (which creates non-toxicalanineinstead of ammonia), convert ammonia to non-toxicglutamine, and get rid of ammonia by excreting it as NH3 gas.The pond loach is also relatively insensitive to ammonia, though it is not known how pond loach tissues, especially the heart and brain, are able to function at ammonia concentrations that would be lethal for other species. One hypothesis is that the pond loach may maintain normal brain cell functioning by altering the sensitivity and specificity of receptors in the brain for potassium ions, which otherwise would be overwhelmed by ammonia.
The pond loach can reproduce sexually and asexually.  Although sexually reproducingdiploids(2n = 50) are most common in Japan, asexual clones also occur in a few wild populations.Clonally reproducing diploid loaches produce unreduced diploid eggs that develop into identical clones (without any genetic contribution from sperm) by the process ofgynogenesis.During gynogenesis, an egg is activated by a sperm that degenerates without fusing with the egg nucleous, so that the resulting embryo contains only maternal chromosomes.  This asexual process involves the duplication of chromosomes by mitosis withoutcytokinesisprior tomeiosis, i.e. premeiotic endomitosis, followed by a quasi-normal meiosis to produce diploid eggs.
Pond loaches are quite active, athletic swimmers, with their activity levels, allegedly, being influenced by oncoming storms or changes inbarometric pressure(hence the name "weather" loach). They are generally active throughout the day, only resting intermittently, but become notablycrepuscularandnocturnalas the day progresses, foraging and swimming more actively in the hours between sunset and sunrise. For this reason, manyaquaristsand keepers will adjust their fishes' communal feeding time to be in the evening, an important point to consider if cohabitating pond loaches with other species. When not resting out-of-sight, pond loaches can often be seen laying on the surfaces of larger-leaved plants (such asAnubias,EchinodorusorNymphaeasp.), on driftwood, or on smooth rocks, and often in comedic or ridiculous positions. They may even appear lifeless, laying on their sides or back, before suddenly springing back to "life" and continuing with their routine behavior. This "playing-dead" style of rest is also well-known from other related species, like the clown loach (Chromobotia macracanthus).
The pond loach is an exceptionally peaceful, hardy species, capable of withstanding unheated aquariums, and preferring to live in outdoor ponds. Not being a tropical species by nature, water temperatures above 70 °F to 75 °F (21.11 °C to 23.89 °C) are not recommended for, and can cause respiratory issues, fatigue, and even death, in pond loaches. For this reason they make a viable companion species for goldfish, which also are a cold-water species. They show virtually no aggression or hostility to any other tankmates, including their own kind, mostly minding their own business despite being a highly sociable species; if housing multiple individuals, which is usually recommended, pond loaches will often "cuddle" and rest huddled-together. The species is widely sold at pet stores and local fish shops. Given their somewhat "goofy" and cantankerous nature, they are not particularly aloof or shy, and thus can develop a "friendliness" towards their caretakers, swimming around their owner's hands and arms, allowing for physical contact and even hand-feeding.
The larger a pond loach matures, the more muscular and likely tobreachthe waters surface they become; due to their jumping prowess, the average aquarium cover should be secured with tape or additional sheets of acrylic or plastic, or panes of additional glass. If kept outside, proper netting over the water feature may be required. If a pond loach successfully jumps from the water (and is not subsequently caught by a bird or other animal), it may crawl on the ground for some time, breathing atmospheric oxygen, before eventually suffocating. Despite their ability to move terrestrially between shallow bodies of water in the wild, something many species do (likekillifish), they do not have the same respiratory adaptations as, for example, thelungfishesormudskippers. Also, in an indoor aquarium setting, care must be taken to cover any tubing or pipes that are large enough for a loach to fit inside of, as they may even travel up filtration tubes and become stuck in the filter itself. Pond loaches enjoy digging and burrowing themselves in the substrate of their tank, so make sure that your substrate is fine enough for them to dig in. If you keep live plants in your tank, they will be uprooted by the loaches, so it is a good idea to weight your plants. The pond loach is also peculiar in that it will sometimes bury itself in the substrate during times of stress. This often surprises new owners, as the fish will "disappear" shortly after introduction to the tank only to "reappear" later.
Because of their alleged appetite forsnails, these loaches are commonly perceived as helping to alleviate snail infestations in fish tanks; however, due to their sensitivebarbels, and substrate-sifting method of foraging for buried worms and hiddenbrine shrimp, pond loaches are not nearly as effective against mollusks as the relatedbotiidloaches. Botias possess notably different, downward-pointing snouts with visibly fewer barbels, as they are more active hunters of prey than the bottom-dwelling pond loaches. The botias have evolved perfectly-shaped snouts to fit inside a snail's shell.
The pond loaches prefer a waterpHof 6.5–8.0, but, as a temperate-climate freshwater species, will tolerate far more acidic conditions, even for extended amounts of time, with little negative reactions. This makes the pond loach a great choice for first-time aquariums and for those who want a hardy fish tank able to withstand a few mistakes. This fish should be kept in groups of at least three, as they like to be in physical contact with each other and feel each other with their barbels when they rest.
There are some hybrid varieties bred in captivity, like the golden dojo and the peppered strain (not to be confused with thepeppered loach). Sometimes the pond loach (especially the golden variety) is mistaken for thekuhli loach. The kuhli, however, likes warm tropical temperatures, will tolerate more acidic conditions, and matures at a much smaller four inches (10 cm). Although these two species have numerous differentiating traits, individual kuhli and pond loaches may resemble each other while young and at the usual age and size of what most fish stores market.
The pond loach is a common culinary fish in East Asia, raised on a large scale infish farming.  According to FAO,M. anguillicaudatuswas 30th on the list of most important species in aquaculture, in terms of total weight produced in 2018.
In Korea,chueo-tang(loach soup) is made with pond loach.  The Japanese hotpotdojō nabe, a specialty ofAsakusa, is also made with this.
In China, pond loach is consumed, especially inSichuan province, and known asniqiu.
According to the US Geological Survey,M. anguillicaudatusis native to eastern Asia from Siberia to Northern Vietnam, including Japan.
Imported into Australia in the 1960s as an aquarium species,M. anguillicaudatuswas first detected in the wild in 1980,and its further importation was banned in 1986.M. anguillicaudatusis a declared Class 1 noxious species inNew South Wales,as it has become established in several NSW rivers, including theMurray Riverextending downstream intoSouth Australia.
Between 2010 and 2020M. anguillicaudatuswas found in 10 states of the United States includingAlabamaandGeorgia.The Georgia find was in November 2020inMcNutt CreekinAthenson the border betweenClarkeandOconee.This indicates eastern Georgia is environmentally suitable for it, and so if not stoppedM. anguillicaudatusis expected to spread through the area.That could include the downstream and adjacent rivers, theMiddle Oconee, theNorth Oconee, theOconee Riveritself, theOcmulgee, and theAltamaha.
As of November 2021, according to the U.S. Geological Survey, this species has also been captured from the wild in Illinois (including many captures in the Chicago area), New York, Ohio, Michigan, Washington, Oregon, Maryland, New Jersey, North Carolina, Louisiana, and southern California.