The Bathypelagic Mysid Gnathophausia (Crustacea) 
and Its Distribution in the Eastern Pacific Ocean 
Linda Haithcock Pequegnat 1 
A NEED HAS LONG EXISTED for an improved 
collecting device for capturing the larger and 
more actively swimming bathypelagic animals 
of the sea. The Isaacs-Kidd Midwater Trawl 
was developed at the University of California’s 
Scripps Institution of Oceanography in 1950 
and has largely satisfied this need (SIO Refer- 
ence 53-3, 1953). 
Bathypelagic specimens have frequently been 
captured in the deeper hauls of the standard 
one-meter plankton nets. However, the self- 
depressing midwater trawl, larger and capable 
of greater depths (up to 4000 m) and speeds 
(up to 5 knots) than the standard 1 -meter 
net, has given us more productive samplings 
of the larger bathypelagic forms (Figs. 1 and 
2). In addition, the midwater trawl has cap- 
tured many species of deep-sea fishes not pre- 
viously reported in the Pacific as well as spe- 
cies entirely new to scientific literature — forms 
which apparently have previously eluded cap- 
ture at these depths by traditional, less effective 
collecting devices. 
The midwater trawl collections made by the 
Scripps Institution of Oceanography in the 
eastern Pacific Ocean during the period 1950 — 
5 3 were examined for the presence of the mysi- 
dacean genus Gnathophausia, a striking crim- 
son red crustacean conspicuous in midwater 
trawl hauls from bathypelagic waters. The order 
Mysidacea has been divided into two subgroups 
based upon very widely separating morphologi- 
cal characteristics: the suborder Mysida and the 
phylogenetically more primitive suborder Lo- 
phogastrida. Gnathophausia is the "giant” 
genus in the suborder Lophogastrida, contain- 
ing the largest mysids ever reported. All of the 
species of Gnathophausia are bathypelagic and 
1 Formerly with the Scripps Institution of Ocean- 
ography, University of California at La Jolla, Califor- 
nia. Present address: c/o Department of Oceanog- 
raphy, Texas A & M University, College Station, 
Texas. Manuscript received March 23, 1964. 
are practically never encountered in shallow 
water. 
Specimens of Gnathophausia have been de- 
scribed from as early as the Challenger Expedi- 
tion in 1873-76 (Sars, 1885 and Willemoes- 
Suhm, 1875), and have been reported from all 
parts of the world from such other pre-twentieth 
century expeditions as the Talisman, the Alba- 
tross, the Oceania, and the Investigator. The 
Dana Expedition in 1928-30 and the Discovery 
Expeditions in the 1920’s and 1930’s have re- 
vealed specimens of this genus in greater num- 
bers and from even more widespread locations 
throughout the world. Prior to the Dana Ex- 
pedition relatively few specimens of Gnatho- 
phausia had ever been captured — probably 
fewer than 100 altogether. A total of 1,051 
specimens of Gnathophausia were taken by the 
Dana, adding considerably to ,our knowledge of 
this group of animals. The distribution and 
biology of Gnathophausia is reported in the 
greatest detail to date by Fage (1941) in his 
study of the vast Dana collections. 
Few studies were made of bathypelagic ani- 
mals in the eastern Pacific Ocean prior to the 
development of the midwater trawl and the sub- 
sequent collections made by the Scripps Institu- 
tion during and after its development. Banner 
(1947) reported on one species of Gnatho- 
phausia (involving 24 specimens) from the 
northeastern Pacific off Canada and Alaska, and 
Banner (1954) discussed the distribution of 
two species of Gnathophausia from collections 
made off the California coast by the Allan 
Hancock Foundation. These latter collections 
involved fewer than 30 specimens of Gnatho- 
phausia and were taken from shallower levels 
than those sampled by the midwater trawl. 
The development of the midwater trawl at 
the Scripps Institution has produced a rich col- 
lection of bathypelagic specimens, particularly 
from the eastern Pacific Ocean area. A total of 
400 specimens of Gnathophausia were availa- 
399 
