日本セトロジー研究 (JapanCetology) (15) : 11-16 (2005)

Ovarian Histology of a Young Harbor Porpoiseラ Phocoenaphocoena,

Caught Off the Coast of Funka Bay, Southern Hokkaido

Yoshiharu Honma 1*1, Tatsuo Ushiki 11, Masaei Takeda 1 1, and Takashi Matsuishi "1

!)Division of Microscopic Anαtomy and Bio-imaging, Depαrtment of Ce/lulαr Function,

Ni注αtaUniversiかGraduateSchool of MedicαI and Dentαi Sciences, Niigatα，Niigata 9 51-8510

2)Depαrtment of Marine Biology, Graduate School of Fisheries Science,

Hokkαido University, Hakodate, Hokkaido 041-8611, J,αpαn

{e-mail: vivanαt J@med. niig.αtα－u. ac.jp)

Key words : entrapped cetacean, harbor porpoise, histology

of ovary, Phocoena phocoena, infant porpoiseヲ Us吋iri

Abstract : The ovaries (each 25mm in l巴ngth) of a female

harbor poゅoise,Phocoena phocoena, accidently caught in a

set net on 26 April 2004, were examined histologically to

assess their degree of maturity. The 5巴ctioned cortical region

was occupied巴ntir巴lywith numerous primordial and primarγ

follicles, whereas in the medullarγregion a small number of

secondarγfollicles, thick-walled arteries and thin-walled veins

were apparent. A few atretic follicles were also encountered.

However, mor巴 developedfollicles, such as Graafian follicles,

W巴renot detected. No sec陀torysubstance could be d巴monstrated

in the mucous epithelia of the oviduct and underdeveloped

uterine glands. The specimen appeared to be an infant owing

to its v巴rγimmatureovarian architecture.

Introduction

Material and Methods

The ovaries and associated org加 Sof a young female harbor

porpoise, Phocoena phocoena, (sample No. P0405, I 22cm

in body l巴ngth),were examined. The ovaries, attached to the

bicornate uteri and vagina, were r巴movedand their external

appearance noted. Subsequently, the ovari巴s,oviduct, uterus

and vagina wer巴 refix巴din Bouin’s solutionラ severalblocks

dissected仕omthose organs being d巴hydratedin an alcohol

series. Following embedding in paraffin, they were cut at 5μm

thickness, dyed chiefly with hematoxylin-eosin (HE) double

stain and Masson-Goldner trichrome associated with aldehyd巳

fuchsine (MG-AF) stain, and observed under a light microsco戸

(Leitz Orthoplan).

Observation

External Morphology

Each ovarγ，white in color, had the form of a thin bean-like

disc, without any protrusions, such as corpora lut巴aand c.

albicantia. Th巴 rightlobe measur巴d25 mm in length and

6 mm in width, and weighed 0.5 g, the le仇 being25mm,

8 mm and 0.3 g, respectively. However, the posterior portion

of the left lobe showed a reddish-brown congestion. Adjacent

to and attached to the ovaries, a loose connective tissue bursa

(ampulla) surrounded the fimbriae of the Fallopian tub巴

(oviduct), there being no cl巴arcutdistinction b巴tweenth巴latt巴r

and the uterus. The cervix of the uterus opened to the large,

broadly triangular vagina. These featur巴sare illustratd in Fig. I.

As mentioned previously, several harbor porpoises were

entangled in set nets installed near the coast of Us吋iri,

Hakodate寸1i (formerly Minamikayabe-cho) , facing Funka

Bay, southern Hokkaido, in April 2004 (Honma et al., 2004).

On 26 April, 2004, a harbor porpoise with a caudal wound

died during transpo目ingfrom a fishing boat to the Usujiri

Fisheries Research Station, Hokkaido University. Death seemed

to be from shock, accompanied by heavy bleeding.

Dissection was carried out the following day and the gonads,

preserved in formalin solution, forwarded to the Anatomy

Departm巴nt,Niigata University School of Medicine.

In Jin巴withprevious studies, the developmental stage and Histology

maturity of th巴gonadsof the specimen were determined and Both ovarian lobes showed similar microscopic features.

comparisons made with those of other cetaceans, including The ovary was surround巴dby a thin mesothelial capsule,

harbor po中oisesentrapped and stranded along the Japan巴se so-called germinal epithelium, consisting of a single layer of

coast (Honma et al.ぅ l999a, b; 2000, 2002, 2004) cuboidal cells with deeply stained nuclei.

11品

唱

Ei

Yoshiharu Honma, Tatsuo Ushiki, Masaei Takeda, and Takashi Matsuish1

The cortical portion was occupied entirely by primordial

and, successively, primarγfollicles. The primordial follicles

were characterized by their round to ovoid shape, and a foam-

like and/or finely stippled cytoplasm surround巴dby very

sporadically located follicular cells, the nuclei of which were

stained deeply by hematoxylin or phroxine, whereas the primary

follicles were enveloped in a few flattened c巴lls (Fig.2 A,

B).

Fig. I. Diagrammatic illustration of the disposition of the genital

organs of a young female harbor porpoise, Phocoena phocoena ( l 22cm long), caught in a set n巴tinstalled off

Us吋iri,Funka Bay, southern Hokkaido, Japan. Ventral

vrew.

c. cervix; f. fimbriae; Ft. Fallopian tube (oviduct); o.

ovary; u. uterus; v. vagina.

Near the stromal portion, larger follicl巴Ssurrounded by

multilayered cuboidal epithelial cells were apparent. Th巴

coarsely granular follicular cytoplasm also contained fine

stipples distributed throughout, a structural pa肘 m consistent

with that of secondary follicles (Fig.2C). The nucleus of

each primordial, primarγand secondary follicle included a

prominent nucleolus.

Verγfew atretic follicles, derived from secondary follicles

with variously disordered巴pithelia,were apparent. Within

those atr巴ticfollicles encountered, amorphous homogeneous

masses reacting positively to AF were detected (Fig.2D).

Fig.2, A～D. Section from the ovary.

A. Part of ovarian cortex showing primordial follicl巴ssurround巴dby sporadically located, flat epithelial cells ( aπows).

Hematoxylirト巴osin(HE) stain.

B. Part of cortex showing primary follicles surrounded by simple layered flat epith巴lium(aπows). HE.

C. Early phase of secondary follicles surrounded by doubl巴layered巴pitheliaconsisting of cuboidal cells (arrows) HE.

D. An atretic follicle surrounded by multilayered epithelia containing a deg巴nerateoocyte ( aπow head) and AF-positive

substance (mucopolysaccharide) in the follicular cavity (asterisk). MG-AF.

Scale bar 25μm

円ノ白

喝！ム

Ovarian histology of a young harbor porpoise, Phocoena phocoen久 caughtoff the coast of Funka Bay、southernHokkaido

Fig.3. A～ D. Section through the oviduct to uterus.

A. Part of ovarian medulla near the fimbria巴 showinga large amount of・ interstitial tissue containing simple layered

mucosal glands (arrows). HE.

B. Part of Fallopian tube showing papillate mucosal glands consisting of simple lay巴r巴depithelium (arrows) HE.

C. Part of ampullary portion of oviduct showing highly intricate mucosal glands consisting of high columnar epithelium

(aηows). Note: absence of AF-positive secretory substance. MG・AF.

D. Part of uterus showing underd巴velopeduterine glands with no AF-positive secr巴torysubstance (arrows). MG-AF.

Scale bar 25μm

The main compon巴ntof the medulla was interstitial tissue,

which occurred in large amounts (Fig.3A).

Each Fallopian tube, comprising highly intricate (papillate)

mucosal glands, was constructed from a simple layer of columnar

epithelial cells (Fig.38,C). However, AF positive mucoidal

substance was demonstrated neither in this tissue, nor in the

und巴rdevelopeduterine glands, which were few in numb巴r

and scattered sparsely in the uterus (Fig.JD). Th巴 uterine

glands, consisting of columnar c巴lls,were short and合agmented.

The stromatous tissue of the uterus compris巴dmainly interstitial

tissue and smooth muscles, although the surface of the uterus

was covered with loose connectiv巴 tissue( = perimetrium) .

Sections of spiral arteries were also present in the stromatous

tissue. Significantly, a cornified layer of keratinized cells was

not observed.

百1巴ovaryand fimbriae of each Fallopian tub巴we陀 enveloped

by a loose connective tissue bursa (ampulla)

Discussion

Harbor porpoises are widely distributed off Japan, and in

th巴NorthPacific and Atlantic (Gaskin et al., 1993; Trippel

et al., 1996). On account of th巴irslightly l巴SS巴ragility

compared with other oceanic dolphins and porpoises, the

Sp巴cieshas not been a target of spear fishing in northern

Japan. However, wounded individuals have been very rarely

found among those stranded Niigata District, Sea of Japan

(Honma et al., 1992, 2002) . On th巴 otherhand, in the Bay

of Fundus, Atlantic coast of North America, incidentally

caught of th巴harborpo巾oisesby the gill-net fishery chiefully

during summer was investigated and analyzed (Trippel et al.,

1996)

Not with stranding, records for the month of April (prior

to the May/June breeding season) over r巴centyears have

indicat巴dthat very few porpois巴shav巴beenentrapped by set

nets installed off th巴 coastof Hokkaido (Honma et al, 2004).

In th巴caseof s巴tnets installed near Usujiri Fisheries Station

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Yoshiharu Honma, Tatsuo Ushiki, MぉaeiTakedaラ加 dT紘ashiMatsuish1

(Hokkaido University), memb巴rsof the Hokkaido University

Cetacean Research Group work to facilitate the recovery of

entrapped individuals, resulting in most being liberat巴dto the

open sea or transported to commercial aquaria in Hokkaido.

However, in spite of careful treatment, some individuals have

perished, as reported by Honma et al. (2004) and h巴rein.

In spite of the slightly small巴rbody size of the present

specimen compared with specimens entrapped similarly by

set nets at Us吋iri,the size of the ovaries was nearly the same

(Honma et al., 2004). However, developmental aspects, in

particular the number of secondary and atretic follicles, seemed

to be less mature.

Compared with a smaller individual stranded on the Niigata

coast, the ovaries of the present specimen were larger (Honma

et al., 2002). In addition, secondary follicles were absent in

the Niigata specimen. Although AF-positive granules were

infrequently encounter巴din the uterine glands of the Niigata

specimen, no such granules were apparent in Us吋irispecimens

examined. Accordingly, all female harbor porpoises examined

histologically by us have been diagnosed as infants owing to

their very immature ovarian and accessory organ conditions.

During the course of on-going histological studies on the

reproductive organs of stranded and captured marine mammals,

all of the individuals examined wer巴 eitherimmature or senile,

no mature animals with sexually active reproductive organs

having been obtained (Honma et al., 1992, 1995, I 999a, b;

2000, 2001, 2002, 2005) As discussed previously, the reason

why no mature animals have been encounter巴dis still unclear

(Honma et al., 2004).

Histological studies of cetacean ovaries加 dassociated organs

have been made by many investigators : Jacobson ( 1941)

on Balenoptera musculus, Dempsey and Wislocki ( 1941)

on Megaptera nodosa, Harrison-Matthews ( 1948) on

balaenopterids, Harrison ( 1949) on Globicephala melaena,

Chittleborough ( 1954) on Aよnodosa,Uys and Best ( 1966)

on whales, Best ( 1967) on Physeter catodon, Simpson and

Gardner (1972) on many species, Mossman and Duke ( 1973)

on both toothed-and baleen whales, Marsh and Kasuya

( 1984) on Globicephala macrorhynchus, lvashin (1984) on

dolphins and whales and Claver et al. ( 1992) on Lagenor砂防hus

australis. Among them, detailed ovarian histology wぉ provided

by Marsh and Kasuya (1984) for G. macrorhynchus. Recently,

Brook et al. (2002) examined ovarian histology in the lndo-

Pacific bottlenose dolphin (Tursiops aduncus) during th巴

reproductive cycle, with emphasis on the appearance of the

corpora albicans.

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On the other hand, Siebert et al. (200 I) and Jauniaux et

al. (2002) reported surveys of post-mo円巴m findings and causes

of death of 500 individual harbor porpois巴saccidentally caught

and/or stranded along the coast of north巴m France, Belgium

and Germany. Both reports pointed out that a high proportion

of th巴harborporpoises investigated compris巴dnewborn (neonate)

and immature individuals, a situation similar to that noted

abov巴

In summation, so as to accumulate histological findings

clarifying the maturity and physiological conditions of stranded

and netted marin巴 mammals,further examinations should

continue to be mad巴．

Acknowledgments

We thank all th巴membersof Hokkaido University Cetacean

R俗図I℃hGroup, Mr. K. Nomw司 Dr.H. Munehara加 dmembers

of Usujiri Fisheri巴sStation, Hokkaido University, Mr. K.

Kagoshima, Mr. M. Aoyama and members of Otaru Aquarium,

Dr. K. Ito of Future University HakodateョS.Nishiwaki of

Institute of Cetacean Research, Japan, Us吋iriFishery Coope国 iv巴

Association, Mr. S. Nomura and all the fishermen ofトfomura

Fishing Company for helping the bycatch survey in Usujiri.

Funding for this work was provided by th巴 SouthHokkaido

Promotion Foundation and JSPS. KAKENHI (15310159,

16657005).

Literature Cited

Best, P.B. (i 967) The sperm whale (Physeter catodon) of

the west coast of South Africa. I. Ovarian changes and

significance. South A合.Div. Sea Fish. Invest. Rep., 61:

1-27.

Brook, F. M., Kinoshita, R., and B巴nieschke,K. (2002)

Histology of the ovaries of a bottlenose dolphin Turciops

aduncus, of known reproductive historγ. Mar. Mammal

Sci., 18: 540-544.

Chittleborough, R. G. ( 1954) Studies on the ovaries of the

humpback whale Megaptera nodosa (Bonnate打巴） , on the

western Australian coast. Aust. J. Mar. Freshwat. Res., 5:

35-63.

Clav巴r,J. A., lnigues, M. A., Lombardo, D. M., and von

Lawzewitsch, I. ( 1992) Prelimimuγobservations on ovarian

activity and sexual maturity in female Peale’s dolphin

(Lagenorhynchus austra/is) Aquat. Mammals, 18: 85-88.

Dempsey, E. W. and Wislocki, G. (1941) The structure of

the ovary of the humpback whal巴 （Megapteranodosa).

Ovarian histology of a young harbor porpoise, Phocoena phocoena, caught o仔thecoast of Funka Bay, southern Hokkaido

Anat Rec., 80: 243-257.

Gaskin, D. E., Yamato, S., and Kawamura, A. (1993) Harbor

porpoise Phocoena phocoena (L.), in the coastal wat巴rsof

northern Japan. U. S. Natl. Mar. Fish. Serv. Fish. Bull.,

91: 440-454.

Har吋son,R. J. ( 1949) Observations on the female reproductive

organs of the Ca'aing whale, Globicepha/a me/aena Traill.

J. Anat., 83: 238・253.

Harrison-Matthews，し（1948) Cyclic changes in the uterine

mucosa of balaenopterid whales. J. Anat., 82 : 207・232.

Honma, Y. (1994) Histological studies on the ovaries of

beaked whales, Mesoplodon stejnegeri, stranded on the

coast of Niigata District, Sea of Japan. Rep. Sado Mar.

Biol. Stat., Niigata Univ., 24：ト10.

Honma, Y., Ushiki, T., Hashizume, H., Takeda, M., Matsuishi,

T., and Honno, Y. (2004) Histological observations on

the reproductive organs of harbor porpoises, Phocoena

phocoena, incidently caught in a set net installed off

Us吋i吋， southernHokkaido. Fish. Sci., 70：・ 94-99.

Honma, Y., Ushiki, T., and Takeda, M. (1999a) Comparativ巴

gonad histology of marine mammals strand巴don th巴coast

of Niigata District, Sea of Japan (East Sea) In: Kwon, H.

B., Joss, J. M. P. and Ishii, S. (eds.) Recent Progress in

Mollecular and Comparativ巴 Endocrinology,Hanrimwon

Publications, Kwangju, 460・464.

Honma, Y., Ushiki, T., Takeda, M., and Shindo, J. (2000)

Ovarian histology of minke whale and Risso’s dolphin

stranded on the coast of Niigata District, Sea of Japan.

Nihonkai Cetol., 10: 23-29.

Honmaヲ Y.,Ushiki, T., Takeda, M., and Shindo, J. (2001)

Notes on a jetfoil collision and strandings of marine

mammals in waters off Niigata, Sea of Japan-1. Nihonkai

Cetol., 11: 31-36.

Honma, Y., Ushiki, T., Takeda, M., and Shindo, J. (2002)

Histological observations on the reproductive organs of a

female harbor porpoise, Phocoena phocoena, strand巴don

the beach at Nishiyamaヲ NiigataPr巴fecture.Nihonkai

Cetol., 12: 25・32.

Honma, Y., Ushiki, T., Takeda, M., and Yamada, T. K.

(1999b) Histological studies on the ovaries of three Pacific

white-sided dolphin, Lagenorhynchus obliquidens, stranded

on the coast of Niigata District, Sea of Japan. Nihonkai

Cetol., 9: 7-14.

Honma, Y. and Yamada, T. ( 1995) Further notes on ovarian

15

histology of the Stejneger’s beaked whale, Mesoplodon

stejnegeri, from a recent stranding on the coast of Niigata

District, Sea of Japan. Bull. Natr. Sci. Mus., Tokyo, Ser.

A, 21: 109-118.

Honma, Y., Yamazaki, Y., Chiba, A., and Oka, S. (1992)

Histological observations on some internal organs of the

harbor porpoise, Phocoena phocoena, stranded on the

Niigata coast, Sea of Japan. Rep. Sado Mar. Biol. Stat.,

Niigata Univ., 22: 1-12.

lvashin, M. V. (1984) Characteristics of ovarian corpora in

dolphins and whal巴sas described by Soviet scientists. Rep.

Intern. Whal. Commn., Spec. Issue, 6: 433-444.

Jacobson, A. P. ( 1941) Endocrine studies in th巴 bluewhale

(Ba/aenoptera muscu/us) . Hvl. Skr. Norske Vid-Acad. I

Oslo, 24: I・84,lpl.

Jauniaux, T., Petitjean, D., Brenez, C., Bo汀ens,M., Borosens,

L., Ha巴lters,J., Tavernier, J., and Coignou, F. (2002)

Post-mortem findings and causes of death of harbor

porpoises (Phocoena phocoena) stranded from 1990 to

2000 along the coastlines of Belgium and northern France.

J. Comp. Pathol., 126: 243・253.

Marsh, H. and Kasuya, T. ( 1984) Changes in the ovaries of

the short-finned pilot whale, G/obicepha/a macrorhynchus,

with ag巴 andreproductive activity. Rep. Intern. Whal.

Commn., Spec. Issue, 6: 311-335.

Mossman, H. and Duke, K. L. ( 1973) Morphology of th巴

Mammarian Ovary. University of Wisconsin Press, 461 pp.

Si巴be口，U., Wu巴nschmann,A., W巴iss,R., Frank, H., Benlく巴，

H., and Frese, K. M. (200 I) Post-mortem findings in

harbour po叩ois巳s(Phocoena phocoena）合omthe German

North Baltic Seas. J. Comp. Pathol., 124: I 02・114.

Simpson, J. G. and Gardner, M. B. (1972) Comparative

microscopic anatomy of selected marine mammals. In:

Ridgway, S. H. (ed.) Mammals of the Sea. Charles C.

Thomas Publications, Springfield, 298・418.

Trippel, E. A., Wang, J. Y., Strong, M. B., Carter, L. S., and

Conway, J. D. ( 1996) Incidental mortality of harbor

porpois巴 （Phocoenaphocoena) by the gill幽 netfishery in

the lower Bay of Funday. Can. J. Fish. Aquat. Sci., 53:

1294-1300.

Uys, C. J. and Best, P. B. (1996) Pathology and lesions

observed in whales flensed at Saldanha Bay, South A仕ica.

J. Comp. Pathol., 76: 407-412.

Yoshiharu Honma, Tatsuo Ushiki, Masaei Takeda, and Takashi Matsuish1

北海道南部噴火湾沖の定置網に混獲された

幼ネズミイルカの卵巣組織像

本間義治］｝・牛木辰男 l）・武田政衛 ll ・松石 隆2)

I）新潟大学大学院医歯学総合研究科細胞機能講座顕微解剖学分野

2）北海道大学大学院水産科学研究科資源管理講座

2004年4月初日に、北海道南部噴火湾の臼尻沖に設置

された定置網に、混獲されたが、回復することなく甲板

上で轄死したネズミイルカ l体の成熟度を知るために、

卵巣とその付属器官の組織像を観察した。双角子宮の卵

管先端に付着した卵巣の皮質部は、原始卵胞と l次卵胞

で占められ、髄質部には少数の 2次卵胞と閉鎖卵が見ら

れた。しかし、グラーフ卵胞は認められなかった。卵管

の粘膜腺や、まだ短管状の子宮腹を構成する高柱状細胞

には、 AF陽性の分泌物が検出されなかった。したがっ

て、この個体はまだ未熟卵巣をもっ幼体と判断された。

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