Neognathophausia ingens (Dohrn, 1870) Common name(s): Deep Water Giant Red Mysid, Giant luminescent opossum shrimp (My name for it--this animal is rarely encountered at the surface)
Synonyms:  Gnathophausia ingens, Gnathophausia bengalensis, Gnathophausia calcarata, Gnathophausia doryphora, Lophogaster ingens
Phylum Arthropoda  Subphylum Crustacea   Class Malacostraca    Subclass Eumalacostraca     Superorder Peracarida      Order Lophogastrida       Family Lophogastridae (or Gnathophausiidae)
	A large sub-adult Gnathophausia ingens swimming past a 1-cm grid.  Note that swimming is accomplished with the pleopods, which beat metachronously, and the left and right sides are in opposite phase of beat.  The thoracopods are held tightly against the underside of the thorax.
	(Photo by: Dave Cowles, 1987)

How to Distinguish from Similar Species:  The rostrum is shorter than that of Gnathophausia zoea  and Neognathophausia gigas and is indistinctly denticulate.  Has reduced or no supra-orbital spines.  The spines at the posterolateral margin of the carapace are also shorter than those of Gnathophausia zoea.  Unlike Gnathophausia gracilis, this species does not have prominent dorsal spines on the abdominal segments.  Unlike Neognathophausia gigas, both the anterior and the posterior lobe of the pleural plates are spiniform.

Geographical Range:  Worldwide in tropical and temperate seas, most common in tropical and subtropical zones (mainly fron 40 degrees N to 40 degrees S).  Common bathypelagically off California and West Africa.  Less common in the eastern tropical Pacific and eastern tropical Atlantic than in the equatorial Indian Ocean, probably because of the extremely low oxygen levels in the eastern tropical Pacific at the depths G. ingens inhabits.

Depth Range:  Usually around 500-900 m (brooding females often around 1200 m).  Can be found down to 4000 m.   Juveniles are usually in water from 5 to 8 degrees C.

Habitat:  Bathypelagic

Biology/Natural History:  Lophogastrids were formerly thought to be a type of mysid.  In regions where this species is common, males do not reach the maximum size.  After the instar at which the species reaches sexual maturity (at about 15 cm total length), the females undergo a growth spurt and the males seem to disappear from the population.  This implies that the females may eat the males after copulation.  Very large males seem to be found mainly in areas where the species is scarce and the male may not have encountered and bred with a female.  While brooding eggs, the female sinks down to around 1000-1200 m depth.  She carries the eggs and larvae for about 1.5 years, during which time she loses much organic body mass and is apparently not feeding (Childress and Price, 1983).  The female's eggs account for 61% of the energy she has accumulated over her lifetime.   Another 13% is used during brooding of her young, 6% in cast exoskeletons, and she only retains 20% of her original total energy content after brooding (but her water content is very high).  The species reproduces only once, and the female dies shortly after release of the larvae.  The species has 13 instars.  Intermolt interval varies from 166 to 253 days, depending on the size  (Childress and Price, 1978.

This species lives permanently below the euphotic zone.  Although its water content increases in winter, suggesting fluctuations in food availability, its O:N ratio changes little indicating that its lipid levels remain high and it is not starving (Hiller-Adams and Childress, 1983).  Both its metabolic rate and ammonia excretion decrease with starvation (Hiller-Adams and Childress 1983, Quetin et al., 1980).

Neognathophausia ingens swims primarily with the pleopods, with some participation by the thoracic exopods (Hessler, 1985).  Their activity levels are little affected by pressure (Quetin and Childress, 1980).   The species swims constantly and has a relatively high drag compared to fish (Cowles et al., 1985), but swims at a speed which minimizes energy losses due to drag (Cowles and Childress, 1988).

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 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).

This species often lives in oxygen minimum layers, yet its metabolism is entirely aerobic (Childress 1968, 1969, 1971, Cowles et al., 1991).  To facilitate oxygen diffusion, it maintains a high rate of oxygen flow over its gills and extracts a very high percentage of the available oxygen (Childress, 1971).  Its low rate of aerobic metabolism (Childress, 1971, Cowles, 1987, Cowles et al., 1991) help keep it from building up oxygen debt.  It has greater gill surface area than do most crustaceans and fishes (Belman and Childress, 1976).  The oxygen diffusion distance across the gills is 1.5 to 2.5 microns, comparable to that found in many fishes (Belman and Childress, 1976).  It maintains relatively high rates of blood flow via large circulatory system components.  Its heart rate is similar to that of other similarly-sized crustaceans, and the heart slows as oxygen limitation is reached (Belman and Childress, 1976).  It appears that much of the oxygen in the blood is carried by hemocyanin, which has a high oxygen affinity and cooperativity  and a large Bohr shift (Sanders and Childress, 1990).  Species which live in areas with very low oxygen levels, such as off California, are able to live aerobically at lower oxygen levels than are those from higher oxygen levels such as Hawaii (Cowles et al., 1991).

Predators include the Melanostominid fish Echiostoma barbatum (Sutton and Hopkins, 1996), the Macrourid fish Macrouronus novaezelandiae (Clark, 1985), dwarf sperm whale (Cardona-Maldonado and Mignucci-Giannoni (1999), the Antillean beaked whale (Debrot, 1998), in which it comprised 41% of the stomach contents of a beached individual, and Cuvier's beaked whale (Palacios, 2003).

The rostrum and spines of small individuals are relatively longer than in large individuals.  This led to small individuals originally having been named a separate species, Gnathophausia calcarata.

Gnathophausia ingens 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.  It also retards sexual maturation such as retarded development of oostegites in females and feminizing changes in males.

References:

Pequegnat, L.H., 1965.  The bathypelagic mysid Gnathophausia (Crustacea) and its distribution in the eastern Pacific Ocean.  Pacific Science 19: 399-422
 

General References:
 

Scientific Articles:

Belman BW, Childress JJ (1976) Circulatory adaptations to the oxygen minimum layer in the bathypelagic mysid Gnathophausia ingens. Biol.Bull. 150:15-37

Benson AA, Lee RF (1975) The role of wax in oceanic food chains. Scientific American 232:76-86

Blaxter, JHS, Russell FS, Yonge M, 1980.  The species of mysids and key to genera.  Advances in Marine Biology 18: 6-342

Brandt, A., Muhlenhardt-Siegel, U, Siegel, V (1998)  An account of the mysidacea (Crustacea: Malacostraca) of the southern ocean.  Antarctic Science 10(1) 3-11

Cardona-Maldonado, Maria A. and Antonio A. Mignucci-Giannoni, 1999.  Pygmy and dwarf sperm whales in Puerto Rico and the Virgin Islands, with a review of Kogia in the Caribbean.  Caribbean J. Science 35:1-2 pp 29-37

Casanova JP, De Jong L, Faure E (1998) Interrelationships of the two families constituting the lophogastrida (crustacea:Mysidacea) inferred from morphological and molecular data. Marine Biology 132:59-65

Childress JJ, Nygaard M (1974) Chemical composition and buoyancy of midwater crustaceans as a function of depth of occurrence off Southern California. Marine Biology 27:225-238

Childress JJ, Price MH (1978) Growth rate of the bathypelagic crustacean Gnathophausia ingens (Mysidacea:Lophogastridae) I. Dimensional growth and population structure. Marine Biology 50:47-62

Childress JJ, Price MH (1983) Growth rate of the bathypelagic crustacean Gnathopausia ingens (Mysidacea:Lophogastridae)II.Accumulation of material and energy. Marine Biology 76:165-177

Childress JJ (1968) Oxygen minimum layer:vertical distribution and respiration of the mysid Gnathophausia ingens. Science 160:

Childress JJ (1977) Physiological approaches to the biology of midwater organisms. In: Andersen NR (ed) Oceanic Sound Scattering Prediction. Plenum Press, New York, p 301-324

Childress JJ (1971) Respiratory adaptations to the oxygen minimum layer in the bathypelagic mysid Gnathopausia ingens. Biol.Bull. 141:109-121

Childress JJ (1971) Respiratory rate and depth of occurrence of midwater animals. Limnology and Oceanography 16:104-106

Childress JJ (1975) The respiratory rates of midwater crustaceans as a function of depth of occurrence and relation to the oxygen minimum layer off southern California. Comp.Biochem.Physiol. 50A:787-799

Childress JJ (1995) Trends in Ecology and Evolution. Elsevier Trends Journals 10:30-36

Clark, Malcolm R., (1985)  The food and feeding of seven fish species from the Campbell Plateau, New Zealand.  New Zealand J. Marine and Freshwater Research 19: pp 339-363

Clarke WD (1961) A giant specimen of Gnathophausia ingens (Dohren,1870)(Mysidea) and remarks on the assymmetry of the paragnaths in the suborder lophogastrida. Crustaceana 2:313-324

Cowles DL (1985) An unusual relationship found between swimming velocity and drag in negatively buoyant pelagic crustaceans. 1985 AAAS Annual Meeting Abstracts. American Association for the Advancement of Science, Washington, DC, p 130

Cowles DL (1986) Metabolism of deep-living pelagic crustaceans in relation to depth of occurrence and environmental oxygen levels. EOS, Transactions, American Geophysical Union 67:971

Cowles, David L., 1987.  Factors affecting the aerobic metabolism of midwater crustaceans.  Ph.D. dissertation, University of California, Santa Barbara.  228 pp.

Cowles, David L., Childress, James J., 1988.  Swimming speed and oxygen consumption in the bathypelagic mysid Gnathophausia ingens.  Biological Bulletin 175: 111-121

Cowles DL, Childress JJ, Gluck DL (1986) New method reveals unexpected relationship between velocity and drag in the bathypelagic mysid Gnathophausia ingens. Deep-Sea Research 33:865-880

Cowles DL, Childress JJ, Wells ME (1991) Metabolic rates of midwater crustaceans as a function of depth of occurrence off the Hawaiian Islands: Food availability as a selective factor? Marine Biology 110:75-83

Debrot, Adolphe, 1998.  New cetacean records for Curacao, Netherlands Antilles.  Caribbean Journal of Science 34:1-2 pp. 168-169

DeJong, L. and J.P. Casanova, 1997.  Comparative morphology of the foregut of four Gnathophausia species (Crustacea; Mysidacea; Lophogastrida). Relationships with other taxa.  Journal of Natural History 31:7 pp. 1029-1040

Denton EJ, Gray J (1985) Lateral-line-like antennae of certain of the Penaeidea (Crustacea,Decapoda,Natantia). Proc.R.Soc.Lond.B. 226:249-261

Donnelly J, Stickney DG, Torres JJ (1993) Proximate and elemental composition and energy content of mesopelagic crustaceans from the eastern Gulf of Mexico. Marine Biology 115:469-480

Frank TM, Widder EA, Latz MI, Case JF (1984) Dietary maintenance of bioluminescence in a deep-sea mysid. Journal of Experimental Biology 109:385-389

Fuzessery ZM, Childress JJ (1975) Comparative chemosensitivity to amino acids and their role in the feeding activity of bathypelagic and littoral crustaceans. Biol.Bull. 149:522-538

Hessler RR (1985) Swimming in crustacea. Transactions of the Royal Society of Edinburgh 76:115-122

Hiller-Adams P, Childress JJ (1983) Effects of prolonged starvation on O{-2} consumption, NH{+4} excretion, and chemical composition of the bathypelagic mysid Gnathophausia ingens. Marine Biology 77:119-127

Hiller-Adams P, Childress JJ (1983) Effects of season on the bathypelagic mysid Gnathophausia ingens: water content, respiration, and excretion. Deep-Sea Research 30:629-638

Hopkins TL, Flock ME, Gartner Jr JV, Torres JJ (1994) Structure and trophic ecology of a low latitude midwater decapod and mysid assemblage. Marine Ecology Progress Series 109:143-156

Kathman, R. D., W. C. Austin, J. C. Saltman, and J. D. Fulton (1986)  Identification Manual to the Mysidacea and Euphausiacea of the Northeast Pacific.  Canadian Special Publication of Fisheries and Aquatic Sciences, vol. 93.  411 pp.  Department of Fisheries and Oceans, Ottawa, Canada
 

Mickel TJ, Childress JJ (1982) Effects of pressure and pressure acclimation on activity and oxygen consumption in the bathypelagic mysid Gnathophaysia ingens. Deep-Sea Research 29:1293-1301

Mickel TJ, Childress JJ (1978) The effect of pH on oxygen consumption and activity in the bathypelagic mysid Gnathophausia ingens. Biol.Bull. 154:138-147

Moeller JF, Case JF (1994) Properties of visual interneurons in deep-sea mysid,Gnathophausia ingens. Marine Biology 119:211-219

Moeller JF, Case JF (1995) Temporal adaptions in visual systems of deep-sea crustaceans. Marine Biology 123:47-54

Ortmann AE (1906) Schizopod Crustaceans in the United States National Museum- the Families Lophogastridae and Eucopiidae. Government Printing Office, Washington DC

Palacios, Daniel M., 2003.  Oceanic Conditions Around the Galapagos Archipelago and their influence on cetacean community structure.  Ph.D. dissertation, Oregon State University

Pequegnat, Linda H., 1965.  The bathypelagic mysid Gnathophausia (Crustacea) and its distribution in the eastern Pacific Ocean.  Pacific Science 19:4 399-421

Petryshov, V. V.  (1992)  Notes on mysid systematics (Crustacea, Mysidacea) of Arctic and the north-western Pacific.  Zoologichesky Zhurnal  71:10 pp. 47-58 (In Russian, with English abstract)
(This is the article in which the species was assigned to the genus Neognathophausia)

Quetin LB, Mickel TJ, Childress JJ (1978) A method for simultaneously measuring the oxygen consumption and activity of pelagic crustaceans. Comp.Biochem.Physiol. 59A:263-266

Quetin LB, Ross RM, Uchio K (1980) Metabolic characteristics of midwater zooplanton:ammonia excretion, O:N ratios, and the effect of starvation. Marine Biology 59:201-209

Quetin LB, Childress JJ (1980) Observations on the swimming activity of two bathypelagic mysid species maintained at high hydrostatic pressures. Deep-Sea Research 27A:383-391

Quetin LB, Childress JJ (1981) Oxygen consumption of the bathypelagic mysid Gnathophausia ingens as a function of swimming activity in relation to oxygen and temperature.

Roe HSJ (1984) The diel migrations and distributions within a mesopelagic community in the north east Atlantic. 2. Vertical migrations and feeding of mysids and decapod crustacea. Progress in Oceanography 13:269-318

Sanders NK, Childress JJ (1990) Adaptations to the deep-sea oxygen minimum layer: oxygen binding by the Hemocyanin of the Bathypelagic mysid, Gnathophausia ingens Dohrn. Biol.Bull. 178:286-294

Tattersall WM (1951) A Review of the Mysidacea of the United States National Museum. United States Government Printing Office, Washington, DC
 

Web sites:
 

These juvenile individuals were captured in San Clemente Basin at about 700-800 m depth.  Photo by Dave Cowles, May 1996
Note the two spines at the end of the telson which form a crescent-shaped structure characteristic of Gnathophausia and Neognathophausia
Notice also that the rostrum in this juvenile is longer in proportion to the animal's total length than is the rostrum of the adult female below, but that it is shorter than that of Neognathophausia gigas.

Mysids and Lophogastrids are "opossum shrimps" because the females carry their eggs and young in a thoracic pouch or "marsupium".  The dorsal wall of the pouch is the ventral surface of the thorax,
while the ventral wall is composed of "oostegites", which are inner, plate-like processes (endopods) projecting from the coxa of the thoracic legs of mature females.  The processes overlap one another, forming the pouch.  In this 15 cm female with young, the pouch can be clearly seen.  She is live and swimming with her pleopods.  Photo by Dave Cowles

Here is an even larger, live female with marsupium.  Photo by Dave Cowles, July 1983.

To view an mpg movie showing some of the key features used in identifying Neognathophausia ingens (15.8 Mb), click here.