The deep-sea dragonfish uses invisible teeth to hunt in the pitch-black ocean

Nature · Published 3 October 2026 Swipe more like this →

In short: Stomiiformes are a diverse order of deep-sea fish, ranging from tiny bristlemouths to formidable dragonfishes. Many species possess nightmarish features, including bioluminescent organs and massive, tooth-filled mouths. Remarkably, some have evolved transparent, non-reflective teeth, a clever adaptation that keeps their weaponry hidden from prey in the dark, light-producing depths.

The order Stomiiformes, whose name derives from the Greek for mouth, comprises at least 410 species of ray-finned fishes. These creatures are primarily pelagic, inhabiting deep oceanic waters globally, from temperate regions to the Antarctic. Their morphology is highly varied, yet they share distinctive traits such as large mouths extending past the eyes and the presence of photophores—light-producing organs that often run in rows along their ventral sides. These organs generate light through an enzymatic reaction involving coelenterazine and calcium ions, allowing the fish to produce colors ranging from white to red.

Many stomiiforms engage in a daily vertical migration, ascending toward the surface at night to feed on planktonic invertebrates and small fish, then retreating to the depths at sunrise. This behavior is not universal; some of the largest predators in the order remain in deep waters, ambushing smaller migrating fish. Their life cycles are equally complex, with some species, such as those in the genera Cyclothone and Gonostoma, undergoing sex changes as they mature. Eggs are typically spawned in deep water but float to the surface to hatch, with larvae descending only after completing metamorphosis.

The evolutionary history of these fish is a subject of ongoing research. While fossils like Paravinciguerria date back to the Cenomanian, modern classification has been recently refined. A 2025 study revealed that previous groupings were paraphyletic, leading to the recognition of eight distinct families, including Vinciguerriidae, Stomiidae, and Sternoptychidae. Their phylogenetic placement remains debated, with scientists questioning whether they belong within the superorder Stenopterygii or should be integrated into a broader classification of teleost fishes. Regardless of their exact lineage, their specialized adaptations—from nanoscale tooth structures to elaborate light-refracting organs—remain among the most fascinating examples of survival in the deep sea.

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