DOI

https://doi.org/10.34331/cpops.2023O001

J-STAGE Advance published date: March 29, 2023

A STRIPED DOLPHIN WITH FIN-SHAPED HIND APPENDAGES

Short Communication

SECOND OCCURRENCE OF A DOLPHIN WITH
FIN-SHAPED HIND APPENDAGES FROM WATERS
OFF TAIJI, THE PACIFIC COAST OF JAPAN
Daiki INAMORI (Director)*,Motoi YOSHIOKA (Scientiﬁc Adviser)1,
Hidehiro KATO (Emeritus Director)2, 3
Taiji Whale Museum, Taiji, Higashimuro, Wakayama 649–5171, Japan*Corresponding author: inamori@kujirakan.jp

Key words:

hind appendages, Tursiops truncatus, Stenella coeruleoalba, striped dolphin, Taiji.

Ohsumi and Kato (2008) reported on a very unique bottlenose dolphin (Tursiops truncatus) having
ﬁn-shaped hind appendages, captured from waters oﬀ Taiji (33°35′N, 135°57′E), Wakayama Prefecture,
Japan in 2006. We have currently conﬁrmed the ﬁnding of another such animal with hind appendages
occurring from waters oﬀ Taiji.
The recently discovered dolphin was found among dolphin ﬁsheries harvest in Taiji. The animal
was from a striped dolphin (Stenella coeruleoalba) school which consisted of 20 individuals seen on
January 5th, 2023, 7 nautical miles oﬀ Taiji. The Taiji Whale Museum staﬀs successfully conﬁrmed thedolphin among the 16 dolphins that were visually examined on their ventral surfaces for sex determination.

Fig. 1. Lateral view of the striped dolphin with ﬁn-shaped hind appendages just after an initial dissection(upper), magniﬁed lateral view (left bottom) and ventral view of the appendages (right bottom).
Cetacean Research Center, Graduate School of Bioresources, Mie University, Kurimamachiya, Tsu, Mie 514–8507, JapanTokyo University of Marine Science and Technology, 4–5–7 Konan, Minato-ku, Tokyo 108–8477, Japan
3
Institute of Cetacean Research, 4–5 Toyomi-cho, Chuo-ku, Tokyo 104–0055, Japan
12Cetacean Popul. Stud. (CPOPS), Others
Vol. 4, 2023, 43–44

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INAMORI, YOSHIOKA AND KATO

The dolphin (Taiji Whale Museum serial specimen ID 230105) was a male, 182 cm long; sex wasconﬁrmed by the external shape of genitalia. The hind appendages arose obliquely at both front sidesof the anus slit and were ventrally located about 56 cm (left side, 30.8% of body length) anterior to thenotch of the tail ﬂukes (Fig. 1). They were of similar size and shape, 4.3 cm (left side) to 5.8 cm (rightside) in straight length, with the right one being slightly larger. The shape was similar to that of thepectoral ﬂippers but more sticklike exterior (Fig. 1; left bottom). The ventral aspect of the left side appendage was the same color as the dorsal appearance of the left side ﬁn, while coloration of the rightside one was a lighter shade of gray. Also, we note the white line surrounding the base of both hindappendages, like in the previous animal having such appendages documented in Ohsumi and Kato
(2008). Further details will be followed in later reports.
Body trunk parts including the hind appendages are kept in lab freezer conditions, and lots of tissue
samples, including blood and serum samples are kept frozen and ﬁxed in formalin or ethanol solutions. These are expected to be used in future studies.

References
Ohsumi, S. and Kato, H. 2008. A bottlenose dolphin (Tursiops truncatus) with ﬁn-shaped hind appendages. Mar. Mamm. Sci.
24(3): 743–745. doi: 10.1111/j.1748-7692.2008.00202.x.

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Cetacean Popul. Stud. (CPOPS), Others
Vol. 4, 2023, 43–44