Biology/Natural History: This small species is by far the lightest-colored species of Gnathophausia that I have seen. The light coloration is probably correlated with the shallow depth that the species is found at. The rostrum of this species, as in many Gnathophausia, is proportionately larger in small individuals, as are the spine on the antenna and the branchiostegal spine. The posterior lobe of the pleuron on the second abdominal segment forms a spine which is longer in mature males than in mature females.

(Genus Gnathophausia):Carapace well-developed, anterior margin has spines. Rostrum elongated, triangular in cross-section. Exopod of uropod is divided by a suture near the apex. Antennal scale large, with a distinctly isolated distal part separated from the proximal part by a more or less well-developed articulation. Distal end of antennal scale smooth, with 1 large spine on the external margin. Dactyls of thoracopods 3-8 widened, lanceolate, with 3 spines only on the distal part of the inner margin and 1 spine in the middle of the inner margin. Pleural plates of the sixth abdominal segment not knitted together ventrally. G. longispina: Keel along ventrolateral margin of carapace curves dorsally as it approaches the posterior end of the carapace. There is no spine at the posteroventral margin of the carapace (that margin is rounded). The mid-dorsalkeel of the carapace is not interrupted nor serrated, and continues out onto the rostrum. No spines on the mid-dorsalkeel of the abdominal segments, or only small, posteriorly-directed spines. Two spines on each side of the anterior pleura of the sixth abdominal segment. Antennal spine missing or very small. Large, triangular and pointed branchiostegal spine. Spine on antennal scale projects well beyond the end of the scale and is serrated on both sides. Rostrum up to 70% of the body length. Pleural plates of sixth abdominal segment have two lobes--anteroventral and posteroventral. The last (sometimes called seventh) abdominal segment has a well-developed spine which is associated with the base of the telson. Body length (to orbit) up to at least 5 cm.

China Sea, Eastern Central Pacific, Hawaiian Exclusive Economic Zone, Indonesian Exclusive Economic Zone, Indo-Pacific, Japanese Exclusive Economic Zone, Makassar Strait, Pacific Ocean, Philippines Exclusive Economic Zone, West Central Pacific

Geographical Range: Central and western tropical and warm north temperate Pacific

How to Distinguish from Similar Species: This species is most similar to G. zoea, which has a similar structure on the antennal scale, a similar pattern of keels on the carapace, and similarly structured abdominal segments. However, G. zoea has rounded branchiostegal spines and no spine on the end of the last abdominal segment which is associated with the telson.

Depth range based on 31 specimens in 1 taxon.
Water temperature and chemistry ranges based on 12 samples.

Environmental ranges
  Depth range (m): 150 - 1655
  Temperature range (°C): 4.330 - 15.243
  Nitrate (umol/L): 5.809 - 36.112
  Salinity (PPS): 34.481 - 34.583
  Oxygen (ml/l): 2.153 - 4.345
  Phosphate (umol/l): 0.518 - 2.499
  Silicate (umol/l): 5.251 - 66.495

Graphical representation

Depth range (m): 150 - 1655

Temperature range (°C): 4.330 - 15.243

Nitrate (umol/L): 5.809 - 36.112

Salinity (PPS): 34.481 - 34.583

Oxygen (ml/l): 2.153 - 4.345

Phosphate (umol/l): 0.518 - 2.499

Silicate (umol/l): 5.251 - 66.495
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Depth Range: 150-500 m. Shallower than other Gnathophausia species, may be in the deep scattering layer.

Habitat: Mesopelagic or shallow bathypelagic. Seems to always be found near land.