Cetacean Population Studies

Volume 1, December 2018
Publication Committee
for the Cetacean Population Studies
Tokyo, Japan

Contents
Foreword……………………………………………………………………………………………

1

Full paper
KISHIRO, T.
Satellite tracking of coastal Bryde’s whales Balaenoptera edeni along the southwest
coast of Japan………………………………………………………………………………………

3

NAKAMURA, G., RYENG, K. A., KADOWAKI, I., HAYASHI, R.,
NAGATSUKA, S., HIROSE, A., FUJISE, Y., and HAUG, T.
Comparison of shapes of the white flipper patch between two sub-species of common
minke whales (Balaenoptera acutorostrata)……………………………………………………… 15
Short Note
HIROSE, A., KISHIDA, T., and NAKAMURA, G.
Nasal mucosa resembling an olfactory system in the common minke whale(Balaenoptera acutorostrata)……………………………………………………………………… 25
Archival Index…………………………………………………………………………………… 29
Subject Index……………………………………………………………………………………… 30
Author Index……………………………………………………………………………………… 31
Guide for Authors………………………………………………………………………………… 32

目

次

初めに………………………………………………………………………………………………

1

研究論文
木白俊也
南西部日本沿岸におけるニタリクジラ（Balaenoptera edeni）の衛星追跡……………………

3

中村玄、RYENG, K. A.、門脇一郎、林凌太朗、永塚翔佳、廣瀬亜由美、藤瀬良弘、HAUG, T.
ミンククジラの 2 亜種間における胸鰭白斑の形態学的比較分析…………………………… 15
短報
廣瀬亜由美、岸田拓士、中村玄
嗅覚の存在を示唆するミンククジラの鼻粘膜組織…………………………………………… 25
著者及びタイトル索引…………………………………………………………………………… 29
件名索引…………………………………………………………………………………………… 30
著者索引…………………………………………………………………………………………… 31
執筆要領…………………………………………………………………………………………… 32

Foreword
Remarkable evolution in cetacean studies in recent decades owes much to major journals that have madesignificant contribution to the development of modern cetology: Discovery Reports, published by the
National Institute of Oceanography in the United Kingdom, and Norwegian Whaling Gazette in Norway,
as well as The Scientific Reports of the Whales Research Institute in Japan.
The Scientific Reports of the Whales Research Institute was first published in 1948, a year after the
Whales Research Institute was established. Aiming to share valuable research findings and scientificknowledge worldwide, the publication was formatted in English since its beginning, quite an ambitious
attempt in Japan still recovering from the devastation of World War II.
Since its first publication, a total of 246 scientists contributed 419 scientific papers to The Scientific
Reports of the Whales Research Institute. It is widely acknowledged and appreciated that these scientificpapers were the foundation for the development of cetacean studies worldwide, and in today’s terms, it
was a research journal that had a significant impact factor, or high number of citations. Regrettably, however, The Scientific Reports of the Whales Research Institute was discontinued in 1988 with the 39th
volume after the institute was reorganized into the Institute of Cetacean Research.
In the 30 years since then, various types of journals on cetacean studies have been published globally,each offering different perspectives on scientific research outcomes. As for Japan, no research journal
matching The Scientific Reports of the Whales Research Institute in its quality has been published. It is
probably because many domestic cetologists have sought to publish their papers in international research
journals based outside Japan.
As the global environment surrounding the issue of whaling became increasingly complex, we haveobserved a shift in publishing policies among these journals, rejecting papers whose findings are basedon specific research methods such as lethal sampling. Because of this, no small numbers of papers submitted by biological scientists using samples collected through lethal surveys, even just for some parts, havebeen denied proper reviews. While we agree that animal ethics should be given high priority when writinga research paper, if a paper, the research method of which is allowed under domestic and internationalrules, is rejected, it is a decision made beyond scientific judgment.
Our new journal for cetacean population studies intends to follow the scientific policy of The Scientific
Reports of the Whales Research Institute, that is, to contribute to global development of cetacean studies.
As long as submitted papers conform to scientifically-accepted animal ethics, we do not make distinctions
based on research methods. At the same time, to maintain the journal’s neutrality in the complex global
environment surrounding whaling issues, the journal will be published from a newly organized committee,
rather than as a bulletin type scientific report from a specific research institute. The title of the new journal will be Cetacean Population Studies to be abbreviated CPOPS, and we aim to keep our door wide-open
for researchers worldwide, contribute to the scientific development of resource studies for marine mammals especially focusing on cetaceans, and nurture many aspiring scientists.

Seiji Ohsumi, Ph. D.
Chairman
Publication Committee for the Cetacean Population Studies
Cetacean Population Studies
Vol. 1, 20181

SATELLITE TRACKING OF COASTAL BRYDE’S WHALES

Full paper

SATELLITE TRACKING OF COASTAL BRYDE’SWHALES BALAENOPTERA EDENI ALONGTHE SOUTHWEST COAST OF JAPANToshiya KISHIRONational Research Institute of Far Seas Fisheries, 2 – 12 – 4 Fukuura, Kanazawa, Yokohama,
Kanagawa 236–8648, Japan (Corresponding author: kishiro@affrc.go.jp)

Abstract
To examine the movements of Bryde’s whales, Balaenoptera edeni, in coastal waters off
Japan, satellite tagging was conducted off Kochi, the southwest coast of Tosa Bay from 2004
to 2008, and off Nomaike, on the southwest coast of the Satsuma Peninsula in 2005. Using an
air gun, an Argos satellite tag was attached on the animal from a whale watching boat. A totalof 20 shots were taken at 17 individuals, and tags were successfully attached to 11. Geographical locations from the Argos Satellite were obtained from seven animals. The maximum tracking period was 30 days in Tosa Bay, and 40 days off Nomaike. Most individuals stayed in thesame waters for at least several weeks in the summer season (July to August). However, one
individual moved from Tosa Bay to the Kii Peninsula, and one from Nomaike to the Goto
Islands in the East China Sea. No animals moved to the offshore waters across the Kuroshio
Current. This result supports the current classification of the stock of coastal Bryde’s whales(the East China Sea Stock). Further technical improvements are necessary to increase thetagging success rates and extend the tracking period to investigate movements and distributional
ranges of Bryde’s whales in the coastal waters off Japan.
Key words

Coastal Bryde’s Whale, Satellite Tracking, Movement.

Introduction

Bryde’s whales Balaenoptera edeni are distributed worldwide in warm temperate oceans between
around 40° N to 40° S (Omura, 1959). Currently, at least two genetically distinct forms are recognized(Kato and Perrin, 2009, 2017): coastal Bryde’s whales (B.e.edeni) and offshore Bryde’s whales(B.e.brydei). Coastal Bryde’s whales are distributed in coastal waters around southwest Japan and havebeen utilized in commercial whale watching activities by the local fishermen in southwestern Tosa
Bay, Kochi prefecture since 1989, and in Nomaike, on the southwest coast of the Satsuma Peninsula,
Kagoshima prefecture since around 1996 (Morioka, 2000). Offshore Bryde’s whales are distributed
broadly in offshore waters from the equator to around 40° N in the western North Pacific.
To elucidate the status and stock structure of the coastal Bryde’s whales around Kochi andKagoshima, several studies have been carried out using line transect shipboard sighting surveys, aswell as photo-identification studies, and genetic analyses. The results of these surveys and studies
indicated that Bryde’s whales off Kochi and Kagoshima are an isolated coastal population isolated
from the offshore Bryde’s whales, separated by the Kuroshio Current (Kato et al., 1996; Kishiro et al.,
1997; Yoshida and Kato, 1999; Kato and Kishiro, 1999). Bryde’s whales off Kochi are sighted within
15 nautical miles from the southwest coast of Tosa Bay year round and have apparent seasonal changes
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in density with a peak in the summer season (Kishiro et al., 1997). Bryde’s whales near Kagoshima
are sighted in the regional waters between Koshiki Island and off Nomaike, and are also frequently
sighted during the summer season (Kato and Kishiro, 1999). However questions concerning the seasonal movements and distributional range of Bryde’s whales remain.
The satellite telemetry technique is one efficient way to investigate the migration of marine mammals, and recent development in tagging techniques have increased the opportunity to investigate
animal movements (Mate et al., 2007; Heide-Jørgensen et al., 2001). To examine individual movements and distributional ranges of Bryde’s whales in the coastal waters off Japan, this study applied
this technique to track tagged Bryde’s whales off Kochi and Kagoshima.
An earlier version of the present paper was consisting of the author’s doctoral thesis submitted toTokyo University of Marine Science and Technology.
Materials and Methods

Study area and shipboard surveys
The two study areas off Nomaike, Kagoshima (a) and off Kochi (b) are shown in Figure 1. BothFig. 1. Geographic map of the study area and the main whale watching grounds (shaded area) for
Bryde’s whales off the southwest coast of Japan.

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SATELLITE TRACKING OF COASTAL BRYDE’S WHALES

areas are known as commercial whale watching areas for Bryde’s whales.
Shipboard surveys were carried out using local whale watching boats (5 to 12 GT) off Kochi from2000 to 2015 and off Nomaike from 2001 to 2005. Each survey lasted 3 to 14 days in the summer
season (July to August), which was thought to be the peak migration of the whales in both areas (Katoand Kishiro, 1999). During a survey, 2 to 5 boats were used simultaneously, with 1 to 3 researchers
on board each vessel. The vessel GPS locations, sea surface temperature, and sea weather conditions
were recorded every 15 minutes during the cruises. Using 7 × 50 binoculars and the naked eye, searching was carried out non-randomly. Search area and route of individual vessels was determined daily
based on the weather conditions and sighting information from commercial vessels. When a whale wassighted, the vessels approached to confirm species identification, record the GPS position, determine
group size and behaviors, and take photographs for individual identification.
Tagging device and tracking methods
As a part of the shipboard surveys, satellite tagging was attempted in the waters off Kochi from 2004
to 2008, and off Nomaike in 2005. As per agreement with local whale watching operators, the numberof whales to be tagged was pre-determined to be 2 – 3 animals per year in the respective waters.
A Spot-5 implantable tag with a two-month battery life (Wildlife Computers, USA) was used as theArgos transmitter. A 40 mm air gun (Miroku Machinery Co. Ltd, Japan) was used for tagging (Fig. 2),
with the filling pressure set to 110 kgf/cm2. The forecastle deck was used as the tagging platform. The
tagging dart used in this study consisted of a dart with a 3-bladed tip, an Argos transmitter, and retrievable float (Fig. 3). The float was connected to the dart by a water-soluble string. When the dart hit theFig. 2. Air gun used for attachment of the satellite tags
from 2004 to 2008.

Fig. 3. The satellite tag used for Bryde’s whales from2004 to 2008. Upper photograph indicates Argos transmitter with a dart. Lower photograph indicates the tagwith a retrievable float.
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whale, it was embedded through the blubber into the muscle, the string dissolved, the float detached,
and the antenna of the transmitter was exposed on the body surface. When the target was missed, thedart floated on the sea surface and was then retrieved by a hand net. The dart was coated with povidone
iodine to reduce physical damage and potential infection caused by tagging. The tracking data fromtagged animals were obtained from the Argos satellite.
Animal tagging was carried out following the basic guidelines of the 3R principle for animal
experiments in Japan issued by the Ministry of Agriculture, Forestry and Fisheries.
Results

Tagging results
A total of 20 tagging attempts were carried out, and 11 tags were successfully attached on 11 whales.
In Tosa Bay (off Kochi), a total of 12 shots were made at 12 individuals from 2004 to 2008. Amongthem, 10 darts hit their target, and nine transmitters were successfully attached. For successful tagging,the chase time ranged from 5 to 23 minutes (mean: 14.7 minutes), and shooting distance ranged from
5 to 6 m (mean: 5.3 m). When the darts missed the target, the chase time ranged from 6 to 62 minutes(mean: 33.0 minutes), and shooting distance ranged from 5 to 10 m (mean: 7.6 m).
Off Nomaike, a total of eight shots were taken at five individuals in 2005, and two individuals weresuccessfully tagged. For successful tagging, chase time ranged from 6 to 11 minutes (mean: 8.5 minutes), and shooting distance was 7 m. When the darts missed, chase time ranged from 3 to 79 minutes(mean: 33.5 minutes), and shooting distance ranged from 7 to 10 m (mean: 8.2 m) (Table 1).
Table 1. Results of the tagging for Bryde’s whales in Tosa Bay and off Nomaike from 2004 to 2008.
Schoolsize

Seastate*

Time forchasing(minutes)

49483

1

3

31

10

Hit

Lost

20 Jul. 2004 14:38

49482

1

3

17

6

Hit

Fix

#2

16 Jul. 2005 14:40

57022

2

2

5

5

Hit

Fix

#3

16 Jul. 2005 14:56

57023

2

2

16

5

Hit

Fix

–

20 Jul. 2005 16:02

–

2

2

6

8

Ricochet

Retrive#420 Jul. 2005 16:20

57021

2

2

10

6

Hit

Fix

#5

24 Jul. 2006 13:54

64634

1

3

18

5

Hit

Fix

#6

24 Jul. 2006 15:57

64635

1

2

23

5

Hit

Fix

#7 25 Aug. 2006 12:05

64636

2

2

14

5

Hit

Fix

–

1

3

62

5

Miss

Retrive#8 11 Aug. 2007 16:21

64637

1

2

21

5

Hit

Fix

#9 31 Aug. 2008 15:18

64639

1

3

8

6

Hit

Fix

Area

Whale
ID

Tosa Bay–

18 Jul. 2004 12:31

#1

–

Off
NomaikeShooting
Date

Shooting Argos
TimeID

11 Aug. 2007 12:40–

10 Aug. 2005

9:26

–

1

2

5

7

Miss

Retrive–

10 Aug. 2005 11:17–

same ind.

2

56

7

Miss

Retrive–

10 Aug. 2005 13:56

–

1

2

5

10

Miss

Retrive

57026

1

1

11

7

Hit

Fix

#10 11 Aug. 2005 12:29–

13 Aug. 2005 10:28

–

2

2

3

9

Miss

Retrive–

13 Aug. 2005 11:18–

same ind.

2

53

9

Miss

Retrive–

13 Aug. 2005 11:44–

same ind.

3

79

7

Miss

Retrive

57025

1

3

6

7

Hit

Fix

#11 13 Aug. 2005 12:53* Beaufort scale

6

Shooting
Transmitter
distance Verdicts
attached(m)

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SATELLITE TRACKING OF COASTAL BRYDE’S WHALES

Fig. 4. Example of the tag attachment on a Bryde’s whale. The
tag was attached on 20 July 2004 in Tosa Bay (whale #1), andphotographed on 23 July 2004.

Tags were attached on either side of the body anterior to the dorsal fin (Fig. 4). All targeted whales
swam quickly during chasing, and no behavioral change was observed during or after the tagging
operation.
Transmission received by the Argos Satellite
Table 2 summarizes the results of tag transmissions received by the Argos Satellite. Although 11
tags were successfully deployed, only ten tags transmitted signals that were received by the satellite,
and no signal was obtained from one tag (whale #3). For the ten active tags, the time period between
tag attachment and final reception of the signals lasted from 1 to 40 days, and the number of transmission signals ranged from 2 to 191 (Fig. 5). From this signal data, geographic locations were obtained
17 times from five animals in Tosa Bay, and 19 times from two animals off Nomaike. The accuracy
for these locations was classified and recorded as class 0 (one time), class A (14 times), and class B(21 times) by the Argos data collection and location system. According to the accuracy from a pastcalibration study (class 0: ≥ 1 km; class A: ≤ 46 km; class B: ≤ 73 km (Baba et al., 1997)), the accuracyof this study ranged from 1 km to 73 km.
Table 2. The number of transmission signals received, and locations estimated by the Argos satellite from Bryde’s
whales tagged in Tosa Bay and off Nomaike from 2004 to 2008.
Area

Whale
ID

Tagging
date

Argos
ID

Reception
period(days)

No. ofsignalsreceived

Tracking
period(days)

No. oflocationsestimatedTosa Bay#1

20 Jul. 2004

49482

4

10

4

4

0

2

2

#2

16 Jul. 2005

57022

34

81

30

1

0

1

0

#3

16 Jul. 2005

57023

0

0

–

–

–

–

–

#4

20 Jul. 2005

57021

5

37

0

0

–

–

–

#5

24 Jul. 2006

64634

4

17

4

3

0

3

0

#6

24 Jul. 2006

64635

7

2

0

0

–

–

–

#7

25 Aug. 2006

64636

1

6

0

0

–

–

–

#8

11 Aug. 2007

64637

15

41

13

5

1

2

2

#9

31 Aug. 2008

64639

2

20

2

4

0

2

2

#10

11 Aug. 2005

57026

4

10

2

1

0

0

1

#11

13 Aug. 2005

57025

40

191

40

18

0

4

14

Off
Nomaike

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Accuracy class
0
A B

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KISHIRO

Fig. 5. Frequency distribution of the transmitted signals received by the Argos satellite, withdays from tag attachment on Bryde’s whales. Open bar: Location was determined; closed
bar: Only reception.

Geographical movements of tagged animals
Four out of five animals tagged in Tosa Bay (whale #1, #2, #5, and #9: Fig. 6 a-d) stayed in the Bay
throughout the transmission period (2 to 30 days). One animal tagged in the Bay on 11 August 2007
(whale #8) moved out of the Bay, moving eastward and reaching the east coast of the Kii Peninsula(off Owase) on 19 August, nine days after tagging. It then turned westward and returned to the Bay
by 23 August (Fig. 6 e).
Off Nomaike, two individuals were tracked (Fig. 7 a-b). One individual (whale #10) was locatednear the tagging site the next day; however, no location could be determined after that, even thoughtransmitted signals were sporadically received until two days later. Another individual (whale #11) wastracked for 40 days after tagging. After staying near the tagging site for 15 days (13 to 27 August),#11 moved to the Goto Islands then returned to near the tagging site (29 August), and stayed in thisvicinity until transmitting signals were lost on 21 September.
Re-sightings of tagged animals
One tagged individual (whale #1) was re-sighted during the transmitting period (Fig. 6 a). The loca-

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Fig. 6. Satellite-based movements of five Bryde’s whales tagged in Tosa Bay in 2004 (whale #1), 2005
(whale #2), 2006 (whale #5), 2007 (whale #8), and 2008 (whale #9). Open circles: Positions at tag attachment; closed circle: Positions determined by the Argos satellite; grey triangle: re-sighting positions during
the transmitting period.
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Fig. 7. Satellite-based movements of two Bryde’s whales tagged in the waters off
Nomaike in 2005 (whale #10 and #11). Open circles: Positions at tag attachment;closed circle: Positions estimated by the Argos satellite.

tions determined by transmitted signals (accuracy class A and B) coincided well with actual sighted
positions of the whale.
Two tagged individuals in Tosa Bay were re-sighted years later. Whale #2 was tagged on 16 July
2005, and was re-sighted on 6 August 2007 and again on 23 and 27 July 2008 in the Bay. Whale #4
was tagged on 20 July 2005, and re-sighted on 22 August 2006 and 6 August 2007 in the Bay. Thesere-sightings were determined by Photo-ID (Fig. 8), and it was noted that the tags had fallen off. Tagging scars on the body had healed similarly to old cookie-cutter shark bites (Fig. 8). Animals did notshow any behavioral changes. No problems were observed by approaching the whales in the whale
watching boat, and one (whale #4) remained calm during a 70-minute observation. Whale #2 associated with another individual, and both animals remained calm during observations. These instancessuggested that tagging impacts were not severe or lasting in these animals.
Discussion

The trials and results reported in the present study are the first attempt at the satellite tracking ofBryde’s whales in the coastal waters off Japan. Although the number of transmitted signals was small

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SATELLITE TRACKING OF COASTAL BRYDE’S WHALES

Fig. 8. Re-sightings of two tagged Bryde’s whales in Tosa Bay, with photo ID keys toidentify the animals. White circles indicate the tagging site of the whales. a) whale #2:
Tagged on 16 July 2005, and re-sighted on 27 July 2008; b) whale #4: Tagged on 20
July 2005, and re-sighted on 22 August 2006.

and the tracking period was short, the results suggested that the Bryde’s whales in the coastal waters
did not move long distances, and possibly stayed in Tosa Bay and off Nomaike for at least several
weeks during the summer season (Figs. 6 and 7). East-west movements of one animal from Tosa Bay
to the Kii Peninsula indicated that whales could move beyond the Bay, and their distributional range
possibly expands around the Kii Peninsula along the Pacific coastline. Movements of one animal off
Nomaike to the Goto Islands indicated that the distributional range is possibly wider than the regional
waters off Nomaike in the East China Sea. Both results revealed that the whales stayed in the samegeneral location, with occasional movements to a wider area than the regional waters of Tosa Bay andNomaike.
In the western part of the North Pacific, the Scientific Committee of the International Whaling Commission (IWC) sets two management stocks for the Bryde’s whales: the western North Pacific stockand the East China Sea Stock (International Whaling Commission, 1997). The western North Pacificstock corresponds to the offshore Bryde’s whales distributed in a broad area from the equator to around
40° N and west of 160° W in the North Pacific. The East China Sea Stock corresponds to whales
distributed in the East China Sea. Based on previous studies, the Bryde’s whales off Kochi (in Tosa
Bay) have been treated as an extension of the East China Sea stock, and their range is thought toexpand to at least off Kochi in Tosa Bay (Kato et al., 1996; Kishiro et al., 1997; Yoshida and Kato,
1999; Kato and Kishiro, 1999). However, the tracking results from this study (whale #8) imply thatthe northern limit of their range might expand beyond Tosa Bay, with possible migrations along thecoast to the Kii Peninsula. If so, it would be necessary to re-consider their range to improve management of the East China Sea stock.
Based on the sighting distributions, Kato and Kishiro (1999) suggest that the warm Kuroshio Current
acts as a physical barrier between the two stocks. No whales tagged in this study crossed the Kuroshio
Current towards the offshore waters in the western North Pacific region. Although the sample size wassmall, this result may support the IWC stock classification and suggestion for the Kuroshio as the barrier between the two stocks.
In this study, transmitted signals from the tags and resultant estimated locations were sporadic, andpoor reception by the satellite decreased the accuracy of the estimations. One possible reason might
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be mechanical trouble with the tag caused by the physical shock of deployment or striking the whale
body. Another reason might be the location of tag attachment on the body. In this study, the tags weremainly attached near the base of the dorsal fin. However, the base of the dorsal fin emerges just before
long dives, and is not as frequently exposed compared to anterior parts of the body (around the blowhole). To estimate accurate locations, the satellite needs at least three successive transmitted signals
while passing over the animal. The low frequency of tag exposure caused inadequate signal reception.
If the tag could be attached more anteriorly, the transmission frequency might increase enough to
improve uplink to the satellite.
To elucidate the movements of the whales after the summer season, a longer tracking period isdesired; unfortunately, the maximum tracking period was 30 days in Tosa bay, and 40 days off
Nomaike. It is presumed that tags fell off of individuals after the last signal transmission. To extend
the longevity of the tags, further technical improvements to the dart, such as a modification of the
shape and number of blades, introduction of a flexible mechanism in the anchor blades, and using
adapted materials to prevent biological reactions will be needed. To control the pressure and depth ofdart penetration, use of other shooting gear such as the Norwegian LK-Arts system (e.g. HeideJorgensen et al., 2001; Olsen et al., 2009) that can easily control the filling pressure may also be useful.
Increasing the tagging success rate and extension of the tracking period are desirable for future studies, and further improvements to the darts and shooting gear as mentioned above will be needed. It is
important to continue to monitor whale movements and to build a larger dataset including a greaternumber of individuals. The accumulated data obtained could bring further insight into the movements
and distributional ranges of Bryde’s whales around Japan. In addition, if possible, simultaneous biopsy
sampling and genetic analyses would be valuable for further elucidation and confirmation of stock
structure.
Acknowledgment

The author wishes to express sincere thanks for the assistance of many anonymous researchers,skippers, and staff of the whale watching organizations in Tosa Bay and Nomaike. The field surveys
were conducted by the National Research Institute of Far Seas Fisheries in cooperation with local
prefectural governments and the whale watching organizations as a contract with the Fisheries Agencyof Japan (FAJ). Sincere thanks are due to the FAJ, Kochi Prefectural Government, and Kagoshima
Prefectural Government for providing the opportunity to conduct the surveys.

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Kishiro, T., Kato, H., Miyashita, T., Ishii, I., Nakajima, T. and Shinohara, E. 1997. Abundance of Bryde’s whales off Kochi,
estimated from 1994/95 and 1995/96 sighting surveys. Rep. int. Whal. Commn 47: 575 – 581.
Mate, B., Mesecar, R. and Lagerquist, B. 2007. The evolution of satellite-monitored radio tags for large whales: Onelaboratory’s experience. Deep-Sea Research Part II. 54: 224 – 247.
Morioka, K. 2000. The whale watching business in the Tosa Bay. PP. 260 – 265. In Kato, H. (eds.) Natural History ofBryde’s whales - Japanese Whale Inhabited in the Tosa Bay (In Japanese). Heibon-sha, Tokyo, 308pp.
Olsen, E., Budgell, W. P., Head, E., Kleivane, L., Nøttestad, L., Prieto, R., Silva, M. A., Skov, H., Víkingsson, G. A.,
Waring, G. and Øien, N. 2009. First satellite-tracked long-distance movement of a sei whale (Balaenoptera borealis)in the North Atlantic. Aquat. Mamm. 35: 313 – 318.
Omura, H. 1959. Bryde’s whale from the coast of Japan. Sci. Rep. Whales Res. Inst. 14: 1 – 33.
Yoshida, H. and Kato, H. 1999. Phylogenetic relationships of Bryde’s whales in the western North Pacific and adjacentwaters inferred from mitochondrial DNA sequences. Mar. Mamm. Sci. 15: 1269 – 1286.

Received: February 9, 2018
Accepted: July 27, 2018

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SUBSPECIFIC DIFFERENCES OF THE WHITE PATCH ON FLIPPER OF MINKE WHALE

Full paper

COMPARISON OF SHAPES OF THE WHITEFLIPPER PATCH BETWEEN TWO
SUB-SPECIES OF COMMON MINKE WHALES(BALAENOPTERA ACUTOROSTRATA)Gen NAKAMURA1*, Kathrine A. RYENG2, Ichiro KADOWAKI1,
Ryotaro HAYASHI1, Shouka NAGATSUKA1,
Ayumi HIROSE1, Yoshihiro FUJISE3 and Tore HAUG2
1
Laboratory of Cetacean Biology, Tokyo University of Marine Science and Technology,
4 – 5 – 7 Konan, Minato-ku, Tokyo 108–8477, Japan *(Corresponding author: gnakam1@kaiyodai.ac.jp)
2
Institute of Marine Research, Fram Centre, P.O. Box 6606 Langnes, NO-9296 Tromsø, Norway
3
Institute of Cetacean Research, Toyomi Shinko Building 5F, 4 – 5 Toyomi-cho, Chuo-ku, Tokyo 104 – 0055, Japan

Abstract
The North Atlantic and North Pacific minke whales are regarded as two different subspecies.
In this study we aimed to clarify the morphological differences of the white patch on the flipper
between these subspecies. Morphological measurements were taken from the left flipper ofsexually mature animals, collected from the North Atlantic (N= 15) and the North Pacific(N = 16) oceans. The length between the tip of flipper to the distal border of the white patch
relative to the total flipper length showed no statistical differences between the two subspecies.
However, the length between the tip of flipper to the proximal border of white patch relative tothe total flipper length was significantly larger in the North Atlantic (74.31%) as compared to
the North Pacific (63.62%) minke whales. Also, the mean angle between the proximal boundaryline of the white patch and the longitudinal axis of the flipper was significantly different
between the North Atlantic (70.05 degrees) and the North Pacific (92.29 degrees) minke whales.
These results show that there are clear morphological differences in the white patch of the flipper between the two minke whale subspecies.
Key words

common minke whale, Balaenoptera acutorostrata, flipper, white patch morphology, subspecies, taxonomy.

Introduction

The common minke whale (Balaenoptera acutorostrata) is distributed worldwide and is regarded
as an important marine resource, particularly in the North Atlantic and North Pacific. Taxonomically,
common minke whales are classified into two subspecies: B. a. acutorostrata in the North Atlantic and
B. a. scammoni in the North Pacific. Although a distinctive population exists in the Southern hemisphere, generally known as the “dwarf” minke whale (B. a. subsp.), the taxonomical status of thissubspecies is still under discussion (Rice, 1998). Since external characteristics are important classification criteria for taxonomy, various studies have focused on the differences in these characteristics todistinguish minke whale populations within and between oceans (Omura and Sakiura, 1956; Christensen
et al., 1990; Kato et al., 1992; Nakamura et al., 2014). A unique characteristic of the common minke
whale is the white patch on their flippers. Compared to the North Pacific minke whale, the dwarf minke
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Fig. 1. Examples of typical appearances of minke whale flippers for
the North Atlantic minke whale (top) and the North Pacific minke
whale (bottom). See also photographs in Appendix 1. Scale bars
indicate 10 cm.

whale has much larger white patches which extend to their shoulders. This feature has been used to
distinguish these two subspecies (Arnold et al., 1987; Kato and Fujise, 2000; Arnold et al., 2005).
Nakamura et al., (2015) reported that the shape of the white patch would be a powerful taxonomical
character to morphologically distinguish the stocks in the North Pacific. Horwood (1989) reviewed
and described the differences in the shape of the white flipper patch between the North Atlantic andNorth Pacific common minke whales. Notably, the latter has a small central projection of the whitearea into the black area of the flipper, whereas in the former, the white area is more angled with nosuch projection.
Fig. 1 shows the color patterns of flippers from North Atlantic and North Pacific common minke
whales. These different characteristics of the white patches have not yet been thoroughly describedand compared. Using a photogrammetric method, Nakamura et al. (2014) showed that the white patch
is significantly larger in the North Atlantic common minke whale as compared to the North Pacificone. However, to clarify the morphological differences of flipper between the two common minke
whale subspecies, a more detailed analysis based on unified methodologies and controlled conditions
is needed. The aim of this study was to specify the relative size and differences of the white flipper
patch between the North Atlantic and North Pacific common minke whales, now based on measurements made directly on flippers obtained from animals taken in commercial (North Atlantic) andresearch (North Pacific) catches.
Materials and Methods

The data from North Atlantic common minke whales were collected during Norwegian commercial
whaling operations conducted south of the Svalbard islands during the summer season in 2016 (Fig.
2). The North Pacific common minke whale data were collected from the survey of the second phaseof the Japanese Whale Research Program under Special Permit in the Western North Pacific (commonly known as JARPN II), conducted in the coastal and offshore waters of Japan in 2012 and 201316

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Fig. 2. Location where materials of the North Atlantic and North Pacific minke whales were collected.

(Fig. 2). This research was conducted in accordance with Article VIII of the International Convention
for the Regulation of Whaling, and Japanese law.
To minimize the effects of sex-specific and growth-dependent differences on the white patch, we
analyzed sexually mature female whales only. A total of 15 animals, mean body length 8.07 m (range:
7.2–8.7 m) from the North Atlantic population, and 16 animals, mean body length 7.96 m (range:
7.10–8.68 m) from the North Pacific population were used in this study. Body length was measured
from the tip of the snout to the notch of flukes, rounded to the nearest 10 cm for the North Atlantic
minke whales and the nearest 1 cm for the North Pacific minke whales. Sexual status was determinedby examining ovaries; whales possessing ≥ 1 corpus albicans or corpus luteum were regarded as
sexually mature. The left flipper was removed and photographed. For each photograph, we carefully
ensured that the camera was placed in the upper direction confronting the flipper. Then, the following
lengths were measured in a straight line using a measuring tape to the nearest 0.5 cm: Total flipper
length: The tip of flipper (a) to the end of the articular process of the humerus (c); Measurement point
A: The tip of flipper (a) to the distal border of white patch (A); and Measurement point B: The tip offlipper (a) to the proximal border of white patch (B). Measurement point C (Angle θ) is the angle
between the proximal boundary line of white patch and the longitudinal axis of the flipper. The proximal boundary line of white patch was defined as the line passing from the ventral (B) to dorsal (b)sides of the proximal border of white patch, whereas the longitudinal axis of the flipper is the straightline from the tip of flipper to the end of the articular process of the humerus. This angle was calculated
by a photogrammetric method using the graphic software Canvas X (Fig. 3). T -testing was applied totest the differences between the two subspecies. It was considered that t was significant at P < 0.05.
Standard deviation (S.D.) was adapted to measure the dispersion of the data. All statistical analyses
were carried out using packaged tools in the statistics software R (R Development Core Team 2015).
Results and Discussion

To clarify inter-subspecies differences in the relative size of the white patch, the proportion of Measurement points A and B relative to the Total flipper length in percent, and Measurement point C in
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Fig. 3. Measurement points of the white patch of the left
flipper from the common minke whale. Total flipper
length: The tip of flipper (a) to the end of the articular
process of the humerus (c), Measurement point A: The tipof flipper to the distal border of white patch (A), Measurement point B: The tip of flipper to the proximal border ofwhite patch (B) and Measurement point C (Angle θ): The
angle between the proximal boundary line of white patch(B-b) and the longitudinal axis of the flipper (a-c) were
measured.

Fig. 4. Comparison of the mean values of three measurement points of the white patch on the flipper from theNorth Atlantic and North Pacific minke whales. A and B show relative size of the Measurement point A and B(see Fig. 3) to the Total flipper length.

Table 1. Mean values of each measurement points of white patch on the flipper of the North Atlantic and North
Pacific minke whales.
Relative length between the tip of B. Relative length between the tip ofof A.
flipper to the distal border of white flipper to the proximal border of white
Subspecies Number
samples patch to the total flipper length (%)
patch to the total flipper length (%)

C. AngleΘ(°)

North
Atlantic

15

33.97 ± 3.96

74.31 ± 2.58

70.05 ± 5.74

North
Pacific

16

33.08 ± 3.64

63.62 ± 2.91

92.29 ± 10.15

degrees were compared between the two subspecies.
The mean proportion of Measurement point A relative to Total flipper length was 33.97% (S.D. =3.96) and 33.08% (S.D. = 3.64) in the North Atlantic and North Pacific common minke whales,
respectively. No significant differences were detected (Fig 4-A, Table 1). The mean proportion of
Measurement point B relative to the Total flipper length was significantly larger in the North Atlantic(74.31%, S.D. = 2.58) as compared to the North Pacific (63.62%, S.D. = 2.91) common minke whales(P < 0.01; Fig 4-B, Table 1). The mean of Measurement point C was significantly distinct between
the North Atlantic (70.05 degrees, S.D. = 5.74) and the North Pacific (92.29 degrees, S.D. = 10.15)
common minke whales (P < 0.01; Fig 4-C, Table 1).

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The results of our analysis indicate that clear morphological differences exist in the relative size of
the white flipper patch between the two subspecies. Although the mean relative length of Measurement
point A showed almost the same values between the two subspecies, the relative length of Measurement point B was significantly greater in the North Atlantic common minke whales than in the North
Pacific ones. This indicates that overall, the North Atlantic common minke whales have a relatively
larger white patch area than the North Pacific common minke whales. As mentioned above, the whitepatch of the dwarf minke whales covers its shoulder region and is much larger than that of North
Pacific and North Atlantic common minke whales (Best, 1985; Kato and Fujise, 2000; Arnold et al.,2005). Pastene et al. (2007) reported that dwarf minke whales are genetically closer to the North
Atlantic common minke whales than to the North Pacific ones. Therefore, the shape of the white patch
may well serve as a suitable taxonomic feature to distinguish between subspecies of the common
minke whale.
Acknowledgements

We thank the captain, Mr. Dag Myklebust, and the crew of KATO and Mr. Truls Soløy, the Chairman of the Norwegian Whalers Union for their contribution during sampling in the North Atlantic
Ocean. We also express our gratitude toward the former leaders of the JARPN II Survey; Drs. Genta
Yasunaga and Takeharu Bando of the Institute of Cetacean Research; Chief in biological surveys, Mr.
Shigeo Tabata and Mr. Takahiro Hara of the National Research Institute of Far Seas Fisheries; Mr.
Atsushi Wada and Mr. Tatsuya Isoda of the Institute of Cetacean Research; and the staff of the Kyodo
Senpaku Co., who were largely involved in the offshore surveys. Finally, we sincerely indebted to Dr.
Hidehiro Kato, Professor Emeritus of Tokyo University of Marine Science and Technology for his
supervision throught the present study.
This study was supported by a grant from “Moritani Scholarship Foundation (2018 – 2019)”.

References
Arnold, P. W., Birtles, R. A., Dunstan, A., Lukoschek, V. and Matthews, M. 2005. Colour patterns of the dwarf minke
whale Balaenoptera acutorostrata sensu lato: description, cladistic analysis and taxonomic implications. Mem.
Queensl. Mus. 51: 277–307.
Arnold, P. W., Marsh H. E. and Heinsohn, G. E. 1987. The occurrence of two forms of minke whales in east Australianwaters with a description of external characters and skeleton of the diminutive or dwarf form. Sci. Rep. Whales Res.
Inst. 38: 1–46.
Best, B. P. 1985. External characters of southern minke whales and the existence of a diminutive form. Sci. Rep. Whales
Res. Inst. 36: 1–33.
Christensen, I., Haug, T. and Wiig, Ø. 1990. Morphometric comparison of minke whales Balaenoptera acutorostrata fromdifferent areas of the North Atlantic. Mar. Mam. Sci. 6: 327 – 338.
Horwood, J. W. 1989. Biology and Exploitation of the Minke Whale. CRC Press, Boca Raton, Florida, 248 pp.
Kato, H. and Fujise, Y. 2000. Dwarf minke whales; morphology, growth and life history with some analyses on morphometric variation among the different forms and regions. Paper SC/52/OS3 presented at: 52nd IWC Scientific Committee meeting; June 2000. 30 pp. [Available from the secretariat of IWC]
Kato, H., Kishiro, T., Fujise, Y. and Wada, S. 1992. Morphology of minke whales in Okhotsk sea, Sea of Japan and off
the east coast of Japan, with respect to stock identification. Rep. int. Whal. Common, 42: 437 – 442.
Nakamura, G., Kadowaki, I., Nagatsuka, S., Fujise, Y., Kishiro, T. and Kato, H. 2014. Variation in a color pattern of whitepatch on the flippers of North Pacific common minke whales: Potential application for their interoceanic difference.
La mer 52: 31–47.
Nakamura, G., Kadowaki, I., Nagatsuka, S., Hayashi, R., Kanda, N., Goto, M., Pastene, L. A. and Kato, H. 2016. White
patch on the fore-flipper of common minke whale, as a potential morphological index to identify stocks. Open Journal of Animal Sciences 6: 116–122.
Omura, H. and Sakiura, H. 1956. Studies on the little piked whale from the coast of Japan. Sci. Rep. Whales Res. Inst.
11: 1 – 37.
Pastene, L. A., Goto, M., Kanda, N., Zerbini, A. N., Kerem, D. A., Watanabe, K., Bessho, Y., Hasegawa, M., Nielsen, R.,
Larsen, F. and Palsbøll P. J. 2007. Radiation and speciation of pelagic organisms during periods of global warming:
the case of the common minke whale, Balaenoptera acutorostrata. Mol. Ecol. 16: 1481 – 1495.
R Core Team. 2015. R: A language and environment for statistical computing. R Foundation for Statistical Computing,Cetacean Population Studies (CPOPS)
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NAKAMURA, RYENG, KADOWAKI, HAYASHI, NAGATSUKA, HIROSE, FUJISE AND HAUG

Vienna, Austria. URL http://www.R-project.org/.
Rice, D. W. 1998. Marine Mammals of the World: Systematics and Distribution. Special Publication Number 4 of theSociety of Marine Mammalogy. Allen Press, Lawrence, Kansas, 231 pp.

Received: April 13, 2018
Accepted: November 7, 201820

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Appendices: Appendix 1-1. Pictures of the left flipper of the North Atlantic minke whale.

50cm 50cm

2016Norway_47(7.9m)(7.9m)
2016Norway_47

2016Norway_49(7.7m)(7.7m)
2016Norway_49

2016Norway_50(8.4m)(8.4m)
2016Norway_50

2016Norway_51(8.5m)(8.5m)
2016Norway_51

2016Norway_52(7.2m)(7.2m)
2016Norway_52

2016Norway_53(8.4m)(8.4m)
2016Norway_53

2016Norway_54(7.8m)(7.8m)
2016Norway_54

2016Norway_57(7.3m)(7.3m)
2016Norway_57

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NAKAMURA, RYENG, KADOWAKI, HAYASHI, NAGATSUKA, HIROSE, FUJISE AND HAUG

Appendix 1-2, (continued).

50cm 50cm

22

2016Norway_58(7.7m)(7.9m)
2016Norway_47

2016Norway_59(8.2m)(7.7m)
2016Norway_49

2016Norway_50
2016Norway_60(8.7m)(8.4m)

2016Norway_51
2016Norway_61(8.0m)(8.5m)

2016Norway_52
2016Norway_62(8.5m)(7.2m)

2016Norway_53
2016Norway_63(8.5m)(8.4m)

2016Norway_54
2016Norway_65(8.3m)(7.8m)

2016Norway_57 (7.3m)

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Appendix 1-3. Pictures of the left flipper of the North Pacific minke whale.

50cm 50cm

2016Norway_47
12NPCS-M029(8.1m) (7.9m)

12NPCS-M049(7.1m) (7.7m)
2016Norway_49

2016Norway_50
12NPCK-M011(8.1m) (8.4m)

2016Norway_51
12NPCK-M028(8.1m) (8.5m)

2016Norway_52
12NPCK-M031(8.2m) (7.2m)

2016Norway_53
12NPCK-M037(8.2m) (8.4m)

2016Norway_54
12NP-M014(8.3m) (7.8m)

2016Norway_57
12NP-M046(7.7m) (7.3m)

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Appendix 1-4, (continued).

50cm 50cm

24

2016Norway_47
12NP-M064(7.9m) (7.9m)

13NPCK-M023(7.9m)(7.7m)
2016Norway_49

13NPCK-M028(7.5m) (8.4m)
2016Norway_50

13NPCK-M040(7.7m)(8.5m)
2016Norway_51

2016Norway_52
13NPCK-M049(8.3m) (7.2m)

13NPCK-M052(8.7m)(8.4m)
2016Norway_53

2016Norway_54
13NPCK-M053(7.6m) (7.8m)

13NPCK-M057(8.1m)(7.3m)
2016Norway_57

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EXISTENCE OF OLFACTORY EPITHELIUM IN BALEEN WHALES?

Short note

NASAL MUCOSA RESEMBLING AN OLFACTORYSYSTEM IN THE COMMON MINKE WHALE(BALAENOPTERA ACUTOROSTRATA)
Ayumi HIROSE1, Takushi KISHIDA2 and Gen NAKAMURA1*
1
Laboratory of Cetacean Biology, Tokyo University of Marine Science and Technology,
4 – 5 – 7 Konan, Minato-ku, Tokyo 108–0075, Japan *(Corresponding author: gnakam1@kaiyodai.ac.jp)
2
Wildlife Research Center, Kyoto university, 2 – 24 Tanaka Sekiden-cho, Sakyo, Kyoto 606 – 8203, Japan

Abstract
Although it has long been assumed that modern cetaceans lack nervous system structures thatmediate olfaction, recent studies suggest that mysticetes still maintain olfactory nerves. We
collected samples of the mucous membrane covering the cribriform plate at the bottom of thedorsal nasal meatus from a mature female common minke whale. The samples were then thinsectioned and stained with hematoxylin and eosin. Microscopic observations revealed that the
mucosa was covered with a pseudostratified columnar epithelium with vessels, glands, andnerve plexuses in its lamina propria. These histological characteristics resembled those of theolfactory epithelium in terrestrial mammals, suggesting that mysticetes do indeed possess asense of smell.
Key words

Baleen whale, Olfaction, Histology, Nasal cavity, Olfactory epithelium.

In terrestrial mammals, the external nares and nasal passages function not only as a respiratory organ
but also as an olfactory organ. Meanwhile, cetaceans use their blowhole as a respiratory tract, but theirolfactory system seems to be highly degenerated. Extremely, odontocetes are reported to possess no
nervous systems that mediate olfaction (Glezer, 2002; Oelschläger and Oelschläger, 2009).
In contrast, recent studies suggest that mysticetes can smell in air partly due to the presence of olfactory bulbs in their brain (Thewissen, George, Rosa and Kishida, 2011; Kishida, Thewissen, Usip,
Suydam and George, 2015). The bony nasal passages of mysticetes branch into two sections: theventral nasal meatus, which is broad and connects the blowhole and larynx, and the dorsal nasal
meatus, a narrower passage the posterior part of which leads to the brain case (Godfrey, Geisler and
Fitzgerald, 2013; Fig. 1). Because these structures resemble those of terrestrial mammals, previous
studies support the presence of an olfactory system in mysticetes (Cozzi, Huggenberger andOelschläger, 2016). Analyses of the olfactory marker protein gene further supports this, suggesting theexistence of a functional olfactory system in mysticetes, even albeit much reduced compared withterrestrial mammals (Kishida and Thewissen, 2012; Springer and Gatesy, 2017).
Of the various functions and morphologies of the nasal epithelium, the portion known as the olfactory region affects an animal’s olfactory ability (Kato and Yamauchi, 2003). The olfactory epithelium
is a pseudostratified columnar epithelium composed of three types of cells: basal cells, sustentacular
cells and olfactory receptor cells. Olfactory receptor cells have olfactory cilia projecting into the nasal
cavity which react to odoriferous substances, stimulating the part of the brain known as olfactory bulbs(Wheater, Burkitt and Daniels, 1979) and subsequently the sense of smell will arise. The olfactory
region is located near the cribriform plate of the ethmoid bone with great inter-species variations
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Fig. 1. The positions of mucosa sampling on the cribriform plate. Lateral view of the headshowing structure of the ventral nasal meatus (dark gray), the dorsal nasal meatus (lightgray), and brain case (stripes). There were a series of deep folds at the bottom of dorsal
nasal meatus.

among mammals (Kato and Yamauchi, 2003). There are small serous glands below the olfactory epithelium known as Bowman’s glands, the ducts of which penetrate into the epithelium and opening of
the nasal cavity. Olfactory nerve fascicles are also found in the lamina propria.
Thus, since the presence of an olfactory epithelium indicates the existence of olfaction, it is a goodstarting point in discussing the feasibility of olfaction in mysticetes. In this study, we carried out histological observations (light microscopy) of nasal mucosa samples from the common minke whale todescribe the olfactory anatomy in this species.
We analyzed a female common minke whale (Balaenoptera acutorostrata) with a body length of
7.68 m. This individual was captured in 2016 during the second phase of the Japanese Whale Research
Program under the special permit in the Western North Pacific (JARPNII), and was appeared to besexually matured based on analysis of its ovaries.
Samples were prepared immediately after the animal’s death (approx. within 4.5 h). Since the locationof the olfactory epithelium was thought to be inside the bony nasal passages, the head was separated into
two halves along the mid-sagittal plane using a chainsaw. After carefully locating the right dorsal nasal
meatus, two transverse sections were cut off to remove anterior part of the dorsal nasal meatus and posterior part of the ethmoid bone. Lateral bony parts were also removed, leaving the entire dorsal nasal
meatus inside the specimen. Finally, the specimen was trimmed into a cube of approximately 10×5×20
cm using a hand saw, and the tissues were fixed in 10% formalin and preserved in 70% ethanol.
Three epithelium samples were collected from the mucosa on the cribriform plate. The location of
the cribriform plate was assumed to be the posterior wall of the recess at the bottom of the dorsal nasal
meatus (Fig. 1). Three square pieces of mucosa with 2 – 3 mm thick including the tissue beneath theepithelium were collected from the preserved specimen using a surgical knife. Two samples were collected from the dorsal side of the wall and one from the ventral side.
The epithelial samples were then processed according to standard histological techniques and stainedwith hematoxylin and eosin (H/E). The epithelium was observed under an optical microscope withmagnification of 10 × and 40 × , paying particular attention to whether the epithelial cells consisted ofa pseudostratified columnar epithelium typical of olfactory organs. The thickness of the epitheliumand structure of the lamina propria were also determined.
Dorsal epithelial samples of mucosa, which constituted the posterior wall of the recess, showedfeatures of a pseudostratified columnar epithelium 70 – 80 µm thick (Fig. 2). A similar epithelium wasalso observed on the ventral side; however, the thickness varied. On the dorsal portion of this ventral
sample, the thickness was 80 µm or more, while the ventral portion was approximately 50 µm thick.
Nerve plexuses and glandular cells were observed in the lamina propria in all three samples, and in
one dorsal sample, some of these serum ducts appeared to open into the nasal cavity.
Thickness of the epithelium exceeds 100 µm in some areas, but less than 100 µm in other areas. In

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Fig. 2. Sections showing the epithelium samples from the cribriform plate. Sections were 6 µm
thick and stained with H/E. Scale bars = 50 µm. The lumen (nasal cavity) is located at the topof the pictures. Close-up of epithelial cells (a, b; 40×) and epithelial tissue showing the lamina
propria (c; 10 × ) from the dorsal side of the cribriform plate. Similar images from the ventral
side (d, e, f).

terrestrial mammals, the olfactory epithelium is typically composed of a pseudostratified columnar
epithelium approximately 100 – 120 µm thick (Kato and Yamauchi, 2003). The epithelial samples ofnasal mucosa observed here show the morphological characteristics similar to those in terrestrial mammals.
The lamina propria of the thick pseudostratified columnar epithelium contained numerous glands,
and these glands opened into the lumen in the dorsal sample. Although more detailed examination isrequired to conclude, we assume that these are Bowman’s glands. Numerous blood vessels were also
observed, suggesting a role in helping warm inhaled air. Near these vessels, peripheral nerve fascicles
were also observed. Overall, the distribution of these tissues in the lamina propria resembled the olfactory region of the nasal mucosa in other mammals (Kato and Yamauchi, 2003; Harkema, Carey and
Wagner, 2006; Chamanza and Wright, 2015).
Areas of pseudostratified columnar epithelium were located near the olfactory bulbs. Meanwhile, inmegascopic observations of parasagittal sections of the animal’s head, the bony canal representing theolfactory tract, or anterior elongation of the brain case, faced the olfactory recess. This elongated area
is occupied by the olfactory bulb, and the bone dividing the brain case and bony nasal passage is thecribriform plate of the ethmoidal bone (Thewissen et al., 2011; Godfrey et al., 2013; Ichishima, 2016).
Epithelium samples of nasal mucosa from the cribriform plate therefore resembled the olfactory epithelium in terrestrial mammals, supporting the feasibility of olfaction in mysticetes.
In general, mysticetes have left and right nasal passages completely isolated from each other (Berta,
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HIROSE, KISHIDA AND NAKAMURA

Ekdale and Cranford, 2014), suggesting that left and right nasal passages could serve as independentolfactory organs. That is, since the left and right auditory organs are able to locate a sound source,these two olfactory organs may be capable of locating the origin of an odoriferous substance via different stimuli of chemical substances between the left and right nasal cavities (Kikuta, Sato, Kashiwadani,
Tsunoda, Yamasoba and Mori, 2010). We therefore hypothesize that mysticetes have two nasal openings
with symmetrical nasal passages, which they use in olfaction (Kishida, 2016).
The microscopic structure of the epithelium samples observed in this study strongly supports thepossibility of an olfactory epithelium. However, it should be noted that similar morphologies do notalways suggest an identical function. Further analyses of the role of this epithelium are required toconfirm the existence of olfaction in the common minke whales.
Acknowledgements

We are grateful to Dr. Hideyoshi Yoshida, National Research Institute of Far Seas Fisheries, and Mr.
Yoshiichi Shimomichi, Shimomichi Suisan for the opportunity to collect specimens. We would like toexpress our gratitude to Dr. Yasuhiro Uekusa, the Senshu-Futaba Kai Medical Corporation for his
advice based on medical knowledge. We also thank Dr. Katsumi Isono, Professor Emeritus of Kobe
University for his detailed comments on the manuscript, and Dr. Masahide Hasobe, Tokyo Universityof Marine Science and Technology for his helping in our experiments.

References
Berta, A., Ekdale, E. G. and Cranford, T. W. 2014. Review of the cetacean nose: form, function, and evolution. Anat. Rec.
297: 2205 –2215.
Chamanza, R. and Wright, J. A. 2015. A review of the comparative anatomy, histology, physiology and pathology of thenasal cavity of rats, mice, dogs and non-human primates. Relevance to inhalation toxicology and human health risk
assessment. J. Comp. Pathol. 153: 287–314.
Cozzi, B., Huggenberger, S. and Oelschläger, H. 2016. Anatomy of Dolphins: Insights into Body Structure and Function.
Academic Press, London, 438 pp.
Glezer, I. I. 2002. Neural morphology. p. 98–115. In: Hoelzel, A. R. (ed.) Marine Mammal Biology: an Evolutionary
Approach. Blackwell Science, Malden, 432 pp.
Godfrey, S. J., Geisler, J. and Fitzgerald, E. M. G. 2013. On the olfactory anatomy in an archaic whale (Protocetidae,
Cetacea) and the minke whale Balaenoptera acutorostrata (Balaenopteridae, Cetacea). Anat. Rec. 296: 257 – 272.
Harkema, J. R., Carey, S. A. and Wagner, J. G. 2006. The nose revisited: a brief review of the comparative structure,function, and toxicologic pathology of the nasal epithelium. Toxicol. Pathol. 34(3): 252 – 269.
Ichishima, H. 2016. The ethmoid and presphenoid of cetaceans. J. Morphol. 277: 1661 – 1674.
Kato, Y. and Yamauchi, S. 2003. Domestic Animal Comparative Anatomy Atlas: 1. Yokendo, Tokyo, 315 pp. (In Japanese)
Kikuta, S., Sato, K., Kashiwadani, H., Tsunoda, K., Yamasoba, T. and Mori, K. 2010. Neurons in the anterior olfactory
nucleus pars externa detect right or left localization of odor sources. PNAS. 107(27): 12363 – 12368.
Kishida, T. and Thewissen, J. G. M. 2012. Evolutionary changes of the importance of olfaction in cetaceans based on theolfactory marker protein gene. Gene. 492: 349 – 353.
Kishida, T., Thewissen, J. G. M., Usip, S., Suydam, R. S. and George, J. C. 2015. Organization and distribution of glomeruli in the bowhead whale olfactory bulb. PeerJ. 3:e897.
Kishida, T. 2016. Studying evolutionary biology from the noses of whales. Keio University Press, Tokyo, 123 pp. (InJapanese)
Oelschläger, H. H. A. and Oelschläger, J. S. 2009. Brain. p. 134 – 149. In: Perrin, W. F. et al. (eds.) Encyclopedia of Marine
Mammals Second edition. Academic Press, Burlington, 1316 pp.
Springer, M. S. and Gatesy, J. 2017. Inactivation of the olfactory marker protein (OMP) gene in river dolphins and otherodontocete cetaceans. Mol. Phylogenetics Evol. 109: 375 – 387.
Thewissen, J. G. M., George, J., Rosa, C. and Kishida, T. 2011. Olfaction and brain size in the bowhead whale (Balaena
mysticetus). Mar. Mamm. Sci. 27(2): 282–294.
Wheater, P. R., Burkitt, H. G. and Daniels, V. G. 1979. Functional Histology. A Text and Colour Atlas. Churchill Livingstone,
New York, 278 pp.

Received: April 13, 2018
Accepted: April 25, 201828

Cetacean Population Studies (CPOPS)
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ARCHIVAL INDEXCETACEAN POPULATION STUDIES, TOKYO, JAPANNUMBER 1, December 2018
Kishiro, T. Satellite tracking of coastal Bryde’s whales Balaenoptera edeni along the southwest coast ofJapan 3
Nakamura, G., Ryeng, K. A., Kadowaki, I., Hayashi, R., Nagatsuka, S., Hirose, A., Fujise, Y., and Haug,
T. Comparison of shapes of the white flipper patch between two sub-species of common minke whales(Balaenoptera acutorostrata) 15
Hirose, A., Kishida, T., and Nakamura, G. Nasal mucosa resembling an olfactory system in the common
minke whale (Balaenoptera acutorostrata) 25

Cetacean Population Studies (CPOPS)
Vol. 1, 2018, 29

SUBJECT INDEX

Balaenoptera acutorostrata 1: 15–24
Baleen whale 1: 25–28
Coastal Bryde’s Whale 1: 3–13
common minke whale 1: 15–24
flipper 1: 15–24
Histology 1: 25–28
Movement 1: 3– 13
Nasal cavity 1: 25–28
Olfaction 1: 25–28
Olfactory epithelium 1: 25–28
Satellite Tracking 1: 3–13
Subspecies 1: 15–24
taxonomy 1: 15–24
white patch morphology 1: 15–24

Cetacean Population Studies (CPOPS)
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AUTHOR INDEX

F
Fujise, Y.

1: 15–24

H
Haug, T. 1: 15–24
Hayashi, R. 1: 15–24
Hirose, A. 1: 15–24
Hirose, A. 1: 25–28

K
Kadowaki, I. 1: 15–24
Kishida, T. 1: 25–28
Kishiro, T. 1: 3–13

N
Nagatsuka, S. 1: 15–24
Nakamura, G. 1: 15–24
Nakamura, G. 1: 25–28

R
Ryeng, K. A.

1: 15–24

Cetacean Population Studies (CPOPS)
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