Biology/Natural History: Reach sexual maturity at about 12 cm total length (including rostrum). Spination and relative length of rostrum is greater in smaller individuals, which originally led to small individuals being called the separate species G. drepanephora. This species is less common than is N. ingens off our coast (at least off California)

Lophogastrids were formerly thought to be a type of mysid. This species lives permanently below the euphotic zone. Neognathophausia gigas swims constantly, primarily with the pleopods, with some participation by the thoracic exopods (Cowles, personal observations).

Gnathophausia means "light-jaw". This species has a gland on its second maxillae (mouthparts) from which it spews a brilliantly luminescent cloud into the water when disturbed. Luminescence seems to be a function of diet, since animals of a related species, Neognathophausia ingens, maintained on non-luminescent food in the laboratory gradually lose their ability to luminesce, while if luminescent food is restored they can regain their luminescence (Frank et al., 1984).

Neognathophausia gigas is sometimes parasitized by an ellobiopsid flagellate protozoan, Amallocystis fascitus, which forms a cluster of white filaments on the ventral side of the anterior abdominal segment. The parasite seems to be associated with the main nerve ganglion in this segment, and is associated with hypertrophy of the ganglion. In N. ingens it also retards sexual maturation such as retarded development of oostegites in females and feminizing changes in males.

This bright red lophogastrid mysid has a long rostrum lined with spines. It does not have dorsal spines on the abdomen. The antennal scale is whole, lanceolate, without a distinctly isolated distal part separated from the proximal part by an articulation. The external margin of the antennal scale is serrated, with 3-9 (or 2-7) large spines. Supraorbital spine is well developed. Dactyls of thoracopods 3-8 elongated, lanceolate, with 8-10 spines along nearly the entire length of the inner margin. The pleural plates of abdominal segments 2-5 have a rounded anterior lobe and spiniform posterior lobe. The epimeral plates of the sixth abdominal segment are knitted together ventrally to form an indivisible plate with a deep cleft at the distal end. Maximum length to 16.4 cm. Probably attain maturity at about 12 cm.

Atlantic, Bahia, Bellinghausen Sea, Bouvet Exclusive Economic Zone, Canadian Exclusive Economic Zone [Pacific part], Cape Town, East Indian Ocean, Eastern Central Atlantic, Eastern Central Pacific, FAO fishing area 18, FAO fishing area 67, Gulf of Maine, Hawaiian Exclusive Economic Zone, Indian Ocean, Indo-Pacific, Irish Exclusive economic Zone, Mediterranean Sea, North Atlantic, North East Pacific, North Pacific, North West Atlantic, Northwestern North Pacific, off Japan , Pacific Ocean, South Atlantic, South Georgia, South Indian Ocean, South Pacific, Tristan Da Cunha Exclusive Economic Zone, United Kingdom Exclusive Economic Zone, United States part of the North Atlantic Ocean, West Central Atlantic, West Central Pacific, West Indian Ocean

Geographical Range: Cosmopolitan in tropical and temperate waters (to 60 degrees N and 69 deg S); from S Alaska south in our waters.

How to Distinguish from Similar Species: N. ingens has a relatively shorter rostrum with smaller serrations. Its antennal scale is ovate with small spines. Its supraorbital spine is small or may be absent. Both the anterior and the posterior lobes of the pleuralplates of abdominal segments 2-5 are pointed. Unlike Gnathophausia gracilis, this species does not have prominent dorsal spines on the abdominal segments.

Epipelagic

Bathypelagic

Mesopelagic

Depth range based on 109 specimens in 1 taxon.
Water temperature and chemistry ranges based on 104 samples.

Environmental ranges
  Depth range (m): 0 - 5393
  Temperature range (°C): -1.109 - 13.124
  Nitrate (umol/L): 7.717 - 44.846
  Salinity (PPS): 33.765 - 35.672
  Oxygen (ml/l): 0.790 - 8.065
  Phosphate (umol/l): 0.708 - 3.258
  Silicate (umol/l): 4.198 - 215.449

Graphical representation

Depth range (m): 0 - 5393

Temperature range (°C): -1.109 - 13.124

Nitrate (umol/L): 7.717 - 44.846

Salinity (PPS): 33.765 - 35.672

Oxygen (ml/l): 0.790 - 8.065

Phosphate (umol/l): 0.708 - 3.258

Silicate (umol/l): 4.198 - 215.449
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

Depth Range: 600-4400 m

Habitat: Bathypelagic. Seems to live in waters of approximately 4 degrees C

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 5
Species With Barcodes: 1