Hermaphroditic Skipjack — UCHIDA 
295 
ANTERIOR 
POSTERIOR 
Fig. 2. Oudine of the ovo-testes, showing the loca- 
tion and size of the male and female components 
(ventral view). 
with a compact mass of resorbing ova, while 
the peripheral portion contained ova ranging 
from small, transparent stages to larger, opaque 
ova. The average diameter of 25 randomly se- 
lected larger, opaque ova was 0.504 mm. The 
posterior ovarian sections contained similar 
small and large ova, but no resorbing ova were 
present. Average diameters of randomly selected 
ova from these parts were 0.543 mm. for the 
left posterior member and 0.514 mm. for the 
right. 
The presence of residual ova in the anterior 
section suggests that the fish had been a func- 
tional female. Assuming that the ova in each of 
the ovarian sections ripened at the same time, 
it is possible that ova were extruded from the 
posterior sections at spawning time, whereas 
ova in the anterior section could not be extruded 
because of the lack of an adequate duct. This 
could account for the presence of the resorbing 
ova in the lumen of the anterior ovarian sec- 
tion. Since the testicular sections were well de- 
veloped and constituted a large part of the gon- 
ads, the fish may also have been a functional 
male. 
The discovery of the second pair of ovo-testes 
was reported to the Honolulu Biological Lab- 
oratory on March 10, I960, by Mr. Richard Na- 
kashima of Honolulu, who found them in a 
10-lb. skipjack. 
The gonads, outlined in Figure 3 and labeled 
A and B for purpose of identification, were not 
joined posteriorly as a result of mutilation to 
both posterior ends during removal, and, there- 
fore, could not be identified as to position ( left 
or right ) . Both gonads were distinctly separated 
into three parts; an anterior ovarian section, a 
middle testicular portion, and a torn, fragmen- 
tary ovarian segment posteriorly. The testicular 
segments were similar to those found in the ovo- 
testes previously described, and contained no 
running milt. The ovarian sections were pre- 
dominantly yellow with a tinge of pink. The 
anterior segments were flabby and hollow. 
A starch suspension colored with powdered 
carmine was injected into the posterior ovarian 
section of gonad A and the flow of injected 
material indicated the presence of a duct con- 
necting the two ovarian parts. A similar injec- 
tion was attempted with gonad B, but failed 
MM. 
Fig. 3. Outline of the ovo-testes, showing the 
location and relative size of the male and female 
components. 
