The toothless fish that warns its neighbors of danger using chemical alarm signals

Nature · Published 3 October 2026 Swipe more like this →

In short: The Gonorynchiformes are a diverse order of ray-finned fish, ranging from the commercially vital milkfish to the sand-burrowing beaked sandfish. Despite their lack of teeth, these creatures possess a sophisticated biological toolkit, including specialized gill structures and a unique chemical communication system that alerts nearby fish to potential injury.

The order Gonorynchiformes, whose name derives from the Greek words for angle and snout, occupies a distinct position within the superorder Ostariophysi. These fish are the sole members of the clade Anotophysi. While they share certain anatomical affinities with other ostariophysans, their internal structure is unique. They are defined by a primitive Weberian apparatus—a hearing organ formed by the first three vertebrae and cephalic ribs—though some sources suggest this structure is less developed than the true bony connection found in related groups like carp.

Beyond their skeletal traits, these fish are notable for their specialized physiology. They possess epibranchial organs within their gills and a characteristic caudal skeleton. Perhaps most fascinating is their survival mechanism: when injured, they release a substance from their skin that dissolves into the surrounding water. This chemical signal acts as a warning to other fish in the vicinity, a trait they share with the Cypriniformes. Their physical size is equally varied, with species ranging from 10 to 150 centimeters in length.

The order is currently divided into four extant families: the Chanidae, which includes the milkfish; the Gonorynchidae, or beaked sandfishes; the Kneriidae, known as shellears; and the Phractolaemidae, or snake mudheads. While many modern families are relatively small, the fossil record reveals a deeper history, with various extinct genera dating back to the Late Cretaceous and Early Eocene periods. Whether inhabiting marine environments or freshwater systems in Africa, these toothless fish remain a compelling subject for understanding the evolutionary development of sensory and communication systems in aquatic vertebrates.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• The bony-tongued fish that hunt with electricity and bite with their own mouths
• The world's largest fish family has no teeth, no stomach, and a secret ear
• The tiny, suction-cupped fish that thrives in almost every corner of the ocean
• The tiny, armored fish that build nests with their own biological glue
• The deep-sea dragonfish uses invisible teeth to hunt in the pitch-black ocean
• The goosefish uses a fleshy lure to hunt prey with its cavernous, toothy mouth
• The world's largest frog builds its own stone nests to secure its massive offspring.
• Before the saber-toothed cats, these Permian predators ruled with massive, specialized canine teeth
• The golden pheasant is a master of disguise that prefers running to flying
• Before dinosaurs ruled, these sabre-toothed predators dominated the Permian landscape with terrifying efficiency.
• The golden mole is not a mole, but a master of subterranean sand swimming
• Why these freshwater fish gulp air to survive in oxygen-poor tropical waters

More in Vertebrates · More in Nature · Latest · A–Z · All topics