They are very sexually dimorphic. Females can reach 40cm in length, while the males only reach 5cm. Males have no teeth, no chin barbels, no pelvic fins, and no functioning gut. It's not known how or even if the males eat. It's possible they only live a few weeks, just long enough to mate.
The males live between 1000-2000m below the sea and they always stay in the deep water. The females live around 500m down during the day and move to shallower waters at night.
(These drawings aren't to scale.)
Like many things in living in the deep, black dragonfish can glow. Phosphors are scattered all over their bodies and the chin barbel on the females light up. Unlike other deep sea creatures, black dragonfish can glow green and red. Most other fish only give off a blue
light, but dragonfish use filters and fluorescent material to change the color.
The larval stage is particularly funky looking. The blobs on the end of the stalks are its eyes. The stalk-eyes allow for a greater range of vision, which helps them find food and avoid predators.