STRANGE ORGAN IN THE ANAL REGION OF THE
FINLESS PORPOISE
MASAHARU NISHIWAKI
University of the Rycckyus, Okinawa

AND

KAZUO KUREHAHimeji City Aquarium, Himeji

The Himeji City Aquarium received a telephone call from Mr. Tsuda of Aioi Yacht
Harbor on the morning of October 13, 1974 asking to take over a finless porpoise
which had been caught by a member of the yacht club. The porpoise was foundfloating up and down the surface by a sailing crew near by Karani Is., one of thescattered islands about 20 km to the west of Himeji City 4 km distant from thebeach. Then the crew hauled it with handy net.
When Kureha arrived at the harbor, the porpoise had already been dead.
So, he carried the carcass back for examination. This 114 cm male specimen had
a small hole in the genital aperture just inbetween the anus and the penis opening.
Investigating with a surgical tool, the examiner felt the cavity was about 2 cm
deep and had closed end. Then Nishiwaki was invited to join the examination. The opening hole was on the center line of ventral surface and looked likea small vagina. At dissection, it was found that the hole was the opening of a blindsac 3 mm in diameter and 24 mm in length inside. The sac narrows immediately
at the close end and connected to the hind part of the urinary bladder with thinconnective tissue. There was no organ such as uterus or ovaries besides it nor any
gland found around the sac by naked eyes.
There has been a description on this opening. Dr. K. Mizue of the Nagasaki
University studied on smaller cetaceans in the western waters of Kyushu about ten
years ago. He reported on the finless porpoises caught in Tachibana Bay in hisresearch report-XII that "naturally, males of this species has no nipple slits along
the genital opening, but there is a blind sac just inbetween the genital opening andthe anus." He had a interest on it and would study separately in future. Asked
for further information, Dr. Mizue answered that he had seen 12 males at that
research and seen this organ in every specimen. So, he thought it might be quite
common, not a matter of drawing special attention nor he have kept any specimenof this portion. When he thought back, he was not sure whether all the twelve
porpoises had this hole. Although he thought it was a degenerated nipple, now
he thinks it was not.
Because there is only one specimen of this portion of finless porpoise, it might
be better to leave histological study undone until more specimen will have found.
Here the authors intend to report a finding of the strange sac and want to draw
Sci. Rep. Whales Res. Inst.,

No. 27, 1975, 139-140

140

NISHIWAKI AND KUREHA

attention of scientific collegues to get further information and to know whether thisis an aromatic or civet secretion gland or a harmaphroditic vagina.
REFERENCE~hzuE, K., K. YosHIDA, and Y. MASAKI, 1965.

Neomeris phocaenoides, so-called Japanese" SUNAMERI '',caught in the coast of Tachibana Bay, Nagasaki Pref. Studies on the Little Toothed Whales in theWest Sea Area of Kyusyu-XII. Bull. Fae. Fish., Nagasaki University, 18: 7-29.

EXPLANATION OF PLATE
Fig. I. The 114 cm male specimen of the finless porpoise (Neophocoena phocaenoides).
Fig. 2. Ventral surface of the specimen. N: navel, P: penis opening, H: strangehole, A: anus.
Fig. 3. Dissected genital aparture of the specimen. T: testis, U: urinary bladder,
R: rectum, P: penis, N: navel, A: anus, H: strange hole.

Sci. Rep. Whales Res. Inst.,
No. 27, 1975.

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