Hermaphroditism. in a 'Dolphin-(Prodelphinus caeruleo-albus)
By
MASAHARU NISRIWAKI(Received Feb. 20, 1953)

Although there are many reports on the hermaphroditism in mammals,
it does not seem that any case has ever been reported in whales, I suppose.
I report here a case which was recently by chance.
As a part of my study on the stocks of various whale species, I havebeen seeking for a method of determining the age of toothed whales. Itis wellknown that the tooth of these whales shows in its section a peculiar
structure comparable to the grain of the wood. The idea occurred to me
that this structure might be utilized as the age mark. For the purposeof varifying the varidity of this idea, I selected the dolphin (Prodelphinuscaeruleo-albus) as the material, and have been collecting in the field thedata on body length, development of gonads, condition of teeth, etc. fromlarge numbers of individuals. This species is caught in a great numberin the coastal waters of Japan.
In the course of this study, I examined about 1,200 individuals of
this dolphin which were caught by the "driving-in" method at Kawana,Izu peninsula, Shizuoka Pref., on December 6, 1952. It was among thismaterial that hermaphrodite, 231 cm. in body length, was found.
It is my rule in the field survey to measure body length and determine
the sex of every individual, and examine the gonads and collect the teethof only those individuals for which such data seem necessary: the bodylength is read to the nearest 5 or 10 cm. and the sex is determined fro.m
the appearance of the external genital organs. According to this procedure,
the individual in question was first recorded as a female of 230 cm. As
this body length was considerably great for a female of this species andwell exceeded the average at sexual maturity, I thought to examine its
corpora lutea. Through a median incision made on its belly, I inserted
my hand into the abdominal cavity and felt for ovaries. But what I
felt were the testes, not the ovaries.
Fig. 1 is the photograph of the urino-genital system of this individual.
The external genital organs are perfectly those of the normal female ofthis species: neither the clitoris nor the vulva show anomaly in their shape,size, and relative position to the anus.
The upper part of the vagina terminates in the normal manner inthe uterus, which gradually shrinks towards the upper part. Ligaments
suspend the uterus from a pair of gonads, which are the testes instead ofthe ovaries.

M. NISHIWAKI

216

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Hermaphroditism in a Dolphin

Fig. 2. A section of the right testis of a hermaphroditie of the dolphin;showing the presen,ce of spermatozoa. ( x 600)

The measurement of various external body parts of this hermaphrodite
are shown in Fig. 3.
The body proportions derived from these data resemble the values of
the normal male in the anterior part of the body (the head and thorax).
36.0,
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- - - - - - - - - - - -- - -100.0------------~- - - -- - - - - -I~ -- - -:- - ~Measurements of external body parts of a hermaphrodite of the dolphin (in cm.)

218

M. NISHIWAKIIn the posterior part of the body (the abdomen and tail), however, they
resemble the values of the normal female; this is particularly the case in
the disfances from the notch of tail-flukes to the anus and to the reproductive aperture. As body proportion data for normal individuals arestill scanty, above statements may be subjected to correction when moredata are accumulated.
It has been a common custum among the whalers of the world todistinguish the sexes of the whales they caught. But this is done usually
by observing the external organs; the internal genital organs are examined
only in those relatively few individuals ·which are handred in special
biological investigations. Therefore, there is some possibility that thehermaphrodites of such a degree as the present case were captured but
left unnoticed. Then, the hermaphroditism may not be very rare inwhales, although no case has ever been reported until the present one.
In any case, the present finding has aroused my interest considerably,
though it has little bearing upon the study of whale stocks. If any of
the readers would kindly let me known of his observation on this sort ofanomaly in whales, I should appredate it very much.