[8] It may also serve as an accessory lens (modulated by intrinsic or peripheral muscles), or refract light with an index very close to seawater.

As in related families (e.g. Argentinidae), an epibranchial or crumenal organ is present behind the fourth gill arch.

In all species, a variable number of dark melanophores colour the muzzle, ventral surface, and midline.

These organs glow with a weak light due to the presence of symbiotic bioluminescent bacteria, specifically, Photobacterium phosphoreum (family Vibrionaceae).

The anal fin is either present or greatly reduced, and may not be externally visible; it is strongly retrorse in Opisthoproctus.

They are presumably solitary and do not undergo diel vertical migrations; instead, barreleyes remain just below the limit of light penetration and use their sensitive, upward-pointing tubular eyes—adapted for enhanced binocular vision at the expense of lateral vision—to survey the waters above.

What little is known of barreleye reproduction indicates they are pelagic spawners; that is, eggs and sperm are released en masse directly into the water.

The fertilized eggs are buoyant and planktonic; the larvae and juveniles drift with the currents—likely at much shallower depths than the adults—and upon metamorphosis into adult form, they descend to deeper waters.