Catfishes are generally bottom-dwelling. They are solitary, living alone, and are nocturnal (nahk-TER-nuhl) and active at phylum class subclass • order monotypic order suborder family
Candirus can confuse the outward flow of nitrogen-rich water from a fish's gills with the outward flow of nitrogen-rich urine from a person urinating underwater. The candiru swims up the urinary tract, feeding on blood. The tight space and the spines of its head make it impossible for the fish to turn around or back out, and it dies inside the person, blocking urination and causing extreme pain, massive infection, shock, and often death. Humans who live on the candirus' rivers protect themselves by wearing tight clothing when swimming and by not urinating underwater.
night. Some, however, live far away from the bottom, are active during the day, and may form schools. Catfishes usually engage in courtship activity before spawning, or releasing eggs. They then provide some parental care. Most guarding of eggs and the young is done by males. Sea catfishes carry their eggs in their mouths until they hatch.
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