Some Luminous Fishes of the Genera Yarrella and Polyipnus 
Yata Haneda^ 
Fishes of the genus 'Polyipnus, in the family 
Sternoptychiidae, and of the genus Yarrella, 
in the family Gonostomatidae, like some 
other deep-sea luminous fishes, are furnished 
with numerous luminous organs, which 
usually may be seen on the ventral surface of 
the body. 
Yarrella (Goode and Bean) is a compara- 
tively new genus, in some respects interme- 
diate between the genera Gonostoma and 
Porichthys, and is so called in honor of the 
ichthyologist, William Yarrell, F.L.S. (1789- 
1856). 
In Japan two species of this genus — 
Yarrella hlackfordi illustrius McCulloch and 
Yarrella hlackfordi elongata subsp. nov. — were 
reported by Matsubara (1938). 
The type of the genus Polyipnus is P. spino- 
sus Gunther, which was obtained by the 
vessel ’'Challenger,” between the Philippine 
Islands and Borneo, at a depth of 250 fathoms. 
Many species of these two genera have 
been examined and described. The structure 
of their luminous organs has been known for 
some time, but little or no work has been 
done on the luminous phenomenon of these 
organs. 
I have collected specimens of these fishes 
in Japan, in the bays of Tosa and Sagami, 
since 1935 and, with this living material, have 
been able to observe the phenomenon of their 
luminescence in the dark, to examine the 
structure of their luminous organs, and 
especially to determine whether or not the 
luminescence is due to luminous bacteria. 
^Tokyo Jikeikai Medical College, Tokyo, Japan. 
Manuscript received January 26, 1949. 
The two species upon which I report here 
are Polyipnus stereope Jordan and Starks and 
Yarrella hlackfordi illustrius McCulloch. Usu- 
ally most of these fishes are taken in deep 
water by trawlers, but occasionally they come 
up to the surface during the night. It was on 
such an occasion that I caught Polyipnus 
stereope near the coast of Suzukawa, in the 
Prefecture of Shizuoka, by means of the 
Zibiki-Ami (the Japanese name for a large 
seine net). This procedure enabled me to 
study this fish alive, in the dark. 
I have never been able to take Yarrella 
actually alive, but, although my specimens 
were all dead, they were nevertheless quite 
fresh, having been just caught in the trawlers’ 
nets. 
The principal type of luminous organ con- 
sists of two components. As a rough general- 
ization, one part is a bulb-shaped body lying 
within the muscle of the fish, and the other 
part is a funnel, or parabola-like body, which 
is in contact with the surface of the body and 
arranged on its sides. 
The structure of the luminous organs of 
these two species of fishes is much the same 
as that of other luminous deep-sea fishes such 
as Sternoptyx, Argyropelecus, and Maurolicus. 
It consists of five components as shown in 
Figure 1. These five components are a lumi- 
nous body, a reflector, a color filter, a lens, 
and a pigment membrane. 
Luminous Body 
When sectioned medially, it is seen to con- 
sist of a mass of cells radiating from a central 
point appearing not unlike the closely packed 
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