These light organs contain luminous bacteria and can be "shut off" by the fish using either a dark lid or by being drawn into a pouch.

[2] Flashlight fish are found in tropical ocean waters across the world.

[3] They are typically about 14 cm (5.5 in) in size, although some species can reach twice this length.

[4] This tends to make their collection difficult, and as such they are a poorly understood group.

[5] Anomalopidae were originally divided into 5 distinct species:[6] Anomalops katoptron and Photoblepharon palpebratus, widely distributed in the central and western Pacific Ocean; P. steinitzi from the Red Sea and Comoro Islands; Kryptophanaron alfredi from the Caribbean; and K. harveyi from Baja California.