The Gonostomatidae are a family of mesopelagic marine fish, commonly named bristlemouths or anglemouths. Their common name, bristlemouth, comes from their odd, equally sized, and bristle-like teeth. It is a relatively small family, containing only eight known genera and 32 species. However, bristlemouths make up for their lack of diversity with relative abundance, numbering in the hundreds of trillions to quadrillions. The genus Cyclothone (with 14 species) They have a number of green or red light-producing photophores aligned along the undersides of their heads or bodies.
Description
Bristlemouths are extremely small, measuring on average . Bristlemouths have elongated bodies, small eyes, short snouts, large mouths, and large jaws. The position of the dorsal fin begins in line with the anal fin. The difference between bristlemouths species is found in the intensity of their pigmentation and photophore size. For the majority of the species, the morphology remains the same.
Bristlemouths are mostly dark in pigmentation but at times can display translucently.
Bristlemouths are light emitting fish. Bristlemouths rely on their bioluminescence for different outcomes. Some rely on it to find prey while others use it to avoid predation. However, the most common way that their bioluminescence is used is to signal between fish in the same way people "dance or wear bright colors at the nightclub." The lower jaw of the Bristlemouths is not functional in terms of masticating their prey. It is therefore hypothesized that they swallow their prey tail first.
Bristlemouths are able to efficiently capture their prey due to their bioluminescent nature.
Bristlemouths are protandrous, therefore a male-first hermaphrodite: they begin their lives as males and some of them switch to female. Male bristlemouths are smaller than females.
Taxonomy
Some classifications include the genera Pollichthys and Vinciguerria, but this article follows FishBase in placing them in the family Phosichthyidae. In 2025, a phylogenetic study found the genera Diplophos and Manducus, previously included in the bristlemouths, to form a distinct early-diverging clade within the Stomiiformes, and thus moved them to their own family, the revived Diplophidae.
Some classifications include species in the genus Zaphotias, but these are junior synonyms of the species Bonapartia pedaliota.
{| class="wikitable"
|-
! Genus
! Image
! Species
! Description
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Bonapartia</span>
| 140px
| align=center | 1
| valign=top | There is only one described species in this genus. It grows to a length of SL.
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Cyclothone</span>
| 140px
| align=center | 14
| valign=top | Typically about 3 inches long and found usually at depths exceeding 1000 feet. This genus is thought to be the most abundant vertebrate genus, with estimates of trillions to quadrillions of individual Cyclothone fish.
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Gonostoma</span>
| 140px
| align=center | 3
| valign=top | Marine fish; bathypelagic; depth range 100 - 700 m.
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Margrethia</span>
| 140px
| align=center | 2
| valign=top |
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Sigmops</span>
| 140px
| align=center | 4
| valign=top |
|-
| align=center style="background:rgb(110,110,170)" | <span style="color:white;">Triplophos</span>
|
| align=center | 1
| valign=top | There is only one described species in this genus. It grows to a length of SL.
|}
Fossil genera
thumb|[[Scopeloides, a fossil bristlemouth from Romania]]
The following fossil bristlemouth genera are also known:
- Primaevistomias <small>Prokofiev & Bannikov, 2002</small> (Middle Eocene of the North Caucasus, Russia)
- Kotlarczykia <small>Jerzmańska, 1974</small> (Early Oligocene of Poland)
- Scopeloides <small>Wettstein, 1887</small> (Early Eocene to Early Oligocene of Italy, Switzerland, Poland, Romania, and the Czech Republic)
- Ohuus <small>Sato, 1962</small> (Miocene of Japan)