O. soleatus can grow to a standard length of 10.5 centimetres (4.1 in) and usually live from about 500 to 700 metres (1,600 to 2,300 ft) deep.

[5] Opisthoprocus soleautus has a specialized modification of the intestine by the anus, termed the rectal bulb, that contains bioluminescent bacteria and produces light.

The reflector can be contracted or expanded, controlling the amount of light allowed to pass through the thin part of the scales and into the environment.

[1][10] In the eastern Atlantic, it is most frequently encountered between western Ireland and Mauritania, and between Sierra Leone and Angola.

[12] Opisthoproctus soleatus have been found in the stomachs of beached Soweby's beaked whales (Mesoplodon bidens).

[6] Like other deepwater fish, Opisthoproctus soleatus needs to find its prey in a very poorly-lit environment, and avoid being detected itself by a larger predatory species.

Fishes with large upward-facing eyes likely hunt by detecting the silhouettes of prey above them in contrast to the low amounts of light coming in.

The light produced is shone on a reflector which reflects it downward between the ventral scales to create an effect similar to that of the photophores of other species.

[16] While the exact purpose of this is unknown, it has been proposed that O. soleatus uses this apparatus as a method of camouflage or to communicate with members of their species.

In larvae, the sole is silver, with two lines of black pigment increasing in size laterally towards anus.

This makes it difficult to tell whether the population trend is upwards or downwards, or whether the species is facing any particular threats.