Its most prominent features are the two bean shaped torch-like organs under its eyes containing symbiotic bioluminescent bacteria Candidatus photodesmus katoptron, which the fish can turn on and off by blinking.

[8] Via thorough phylogenetic analysis, the splitfin flashlightfish and its symbiont are a key example highlighting rapid co-evolution and population bottlenecks that suggest an obligately dependent relationship.

[7] Splitfin flashlightfish are found in the western and central Pacific Ocean from the Philippines and Indonesia east to the Tuamotus, north to Japan, and south to the Great Barrier Reef.

It is generally found near drop-offs and caves 200–400 m (660–1,310 ft) in depth,[2] but will move into shallower waters during the winter months.

Researchers have found that in darkness (periods of activity), A. katoptron has high blink frequencies and increases the amount of time light organs are on.

During the day (periods of inactivity), A. katoptron reduces blink frequency and decreases the amount of time light organs are on.

[10] Further research has revealed that the blinking mechanism of the splitfin flashlightfish also assists in keeping a cohesive school of fish together.

In addition to  lateral line sensing, blinking of the light organs also aids A. katoptron in determining the distance between itself and its nearest neighbor in a school.

Observations suggest that this is because of reduced nutrients in the bloodstream, which ultimately supplies the light organs in parallel running capillaries.

[13] Bioluminescence may be lost in captive A. katoptron, but experimental husbandry efforts by the Toledo Zoo have demonstrated that providing adequate food, maintaining stable temperatures, and adding occasional bacterial cultures of Vibrio fischeri (a marine photobacterium) may help the fish regain and/or retain the desired luminosity for viewers.