Oriental Weatherfish

Pond loaches usually range from 10 to 20 cm (3.9 to 7.9 in) in length, although individuals can reach 28 cm (11 in) in standard length; females are generally larger than males.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 of barbels, which are used to sift through silt or pebbles to 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 are bottom-dwelling omnivores whose diet consists largely of small benthic invertebrates and detritus. Stomach-content studies have found aquatic insect larvae, small crustaceans, mollusks, and other invertebrates among their major food items. Pond loaches are very hardy fish that can live in poor-quality water, and can survive short periods of drought by producing a layer of moisture-trapping mucus to 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. …

According to the US Geological Survey, M. anguillicaudatus is native to eastern Asia from Siberia to Northern Vietnam, including Japan.

The pond loach can reproduce sexually and asexually. Although sexually reproducing diploids (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 of gynogenesis. During gynogenesis, an egg is activated by a sperm that degenerates without fusing with the egg nucleus, so that the resulting embryo contains only maternal chromosomes. This asexual process involves the duplication of chromosomes by mitosis without cytokinesis prior to meiosis, i.e. premeiotic endomitosis, followed by a quasi-normal meiosis to produce diploid eggs.

The pond loach is a common culinary fish in East Asia, raised on a large scale in fish farming. According to FAO, M. anguillicaudatus was 30th on the list of most important species in aquaculture, in terms of total weight produced in 2018, but by individual number it is the most farmed fish in the world. In Korea, chueo-tang (loach soup) is made with pond loach. The Japanese hotpot dojō nabe, a specialty of Asakusa, is also made with this. In China, pond loach is consumed, especially in Sichuan province, and known as niqiu.