Luminous Organs of Fish Which Emit Light Indirectly 
Yata Haneda 1 
INTRODUCTION 
There are many reports of luminous 
fishes, all of which, in earlier days, were taken 
from the deep seas. Luminous organs were 
found on the sides of the bodies, on the bar- 
bels, or on the antennae. In outward appear- 
ance these fishes were strangely shaped and 
feebly developed, with soft bones and loose 
muscles, and it was assumed that such un- 
usual fishes belonged exclusively to the deep- 
sea fauna. 
The material examined was invariably 
dead and damaged. It might have been newly 
caught, or else had been preserved in forma- 
lin or in alcohol for an indefinite period. 
There seems to be very little record of 
observation^ on living material, and only the 
morphology of the organs of these fishes was 
studied. The organs were never really under- 
stood, and were mistaken for sensory organs, 
electric organs, or secondary eyes, or they 
were simply referred to as eye-like organs. 
In the early days bacteriological knowl- 
edge, especially knowledge of luminous bac- 
teria, was not far advanced, and fish which 
became luminous after death as a result of 
contamination by saprophytic luminous bac- 
teria were mistaken for true luminous fishes. 
Recent advances in the study of these in- 
teresting problems of luminosity have shown 
that luminous fishes are not confined to the 
deep-sea fauna, but may be found among the 
fauna of the shallow and coastal waters of 
the sea, and that luminosity may be caused 
by luminous bacteria. Moreover these studies 
have revealed that luminous bacteria play an 
important role in the production of light in 
1 Tokyo Jikeikai Medical College, Tokyo, Japan. 
Manuscript received Jafiuary 26, 1949- 
some fishes by entering certain ducts pos- 
sessed by these fishes, and there settling down 
to a symbiotic existence. Within the duct 
they are cultured and utilized as a source of 
light, the fish undergoing some modifications 
to create an organization within itself to dis- 
play the light. Such an association between 
a fish and luminous bacteria constitutes what 
is known as luminous symbiosis. 
Most known luminous fishes are found in 
deep oceanic waters and have on the surface 
of their heads or bodies, or on their barbels, 
or on their antennae, curious arrangements 
of luminous organs of varied shapes, sizes, 
and arrangements. For example the lumi- 
nous sharks have on the side of their bodies 
simple, small luminous dots which consist of 
groups of luminous skin organs. The genera 
Stomias, Chauliodus, and Gonostomias also 
possess numerous luminous dots in the under- 
lying skin in addition to their regular series 
of luminous organs. A Porichtys species has 
rows of many small luminous organs which 
follow the direction of the multiple lateral 
lines. A Pseudoscopelus species has numer- 
ous minute luminous organs arranged in in- 
definite rows of a characteristic shape. The 
lantern fishes ( Myctophidae ) possess fewer 
luminous organs, but these are pearl-like and 
are arranged symmetrically in a series on each 
side of the fishes. In some species of Lam- 
panyctus, luminous scales may be present 
above or below the tail base. Luminous 
patches or ducts occur on the head of Diaphus 
or on the body of Lampanyctus species. The 
Sternoptychidae and Stomiatidae are charac- 
terized by highly developed luminous organs 
of a more complex structure, consisting of a 
luminous body, reflector, lens, and color fil- 
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