Misgurnus fossilis
Weatherfish breathes air through its intestines to survive low oxygen.
Misgurnus fossilis, commonly known as the weatherfish, is a species of true loach with a wide distribution across Europe and parts of Asia. It is notable for its ability to survive in low-oxygen environments by breathing atmospheric oxygen, a trait that allows it to inhabit waters where many other fish cannot live.
- field
- Ichthyology
- known_for
- Atmospheric oxygen breathing through intestines; largest true loach if unconfirmed reports are accurate
- max_length
- Up to 30 cm (12 in); unconfirmed reports up to 45 cm (17.7 in)
- diet
- Omnivorous scavenger; small aquatic invertebrates and detritus
- conservation_status
- Least concern, but protected in most of its range
Lore & Background
The weatherfish (Misgurnus fossilis) is an omnivorous scavenger bottom feeder that uses its sensitive barbels to find food, primarily small aquatic invertebrates and detritus. Its long, thin body allows it to burrow through substrate and navigate spaces that deeper-bodied fish cannot. Adults grow up to 30 cm in total length, though some fishermen claim to have caught individuals up to 45 cm; if true, this would make it the largest species of true loach.
Reader's Guide
The weatherfish occupies a wide range in Europe and parts of Asia, occurring north of the Alps from the Meuse River to the Neva River, as well as in the northern Black Sea basin and Caspian Sea drainages. It is also introduced in some areas, though less extensively than the pond loach. Adults live in dense aquatic vegetation, while juveniles prefer shallow shoreline areas with abundant detritus; neither is found in open, unvegetated water. This habitat dependence makes dredging and weed removal a threat to populations. Despite being listed as least concern, the species is protected across most of its range. Its most remarkable adaptation is the ability to breathe atmospheric oxygen: in low-oxygen conditions, it swims to the surface, gulps air, passes it through the intestines where a complex network of blood vessels extracts oxygen, and expels the air from the anus. This capability enables it to survive in habitats that would be lethal to most other fish.
Did You Know?
- The weatherfish can breathe atmospheric oxygen by gulping air and absorbing it through its intestines.
- If unconfirmed reports of 45 cm specimens are true, Misgurnus fossilis would be the largest species of true loach.
- Adults live in dense aquatic vegetation, while juveniles prefer shallow shoreline areas with detritus.
- Dredging and aquatic weed removal pose a danger to weatherfish populations due to their habitat preferences.
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