CHROMOSOME NUMBER OF TWO COLOR TYPESOF THE DALL'S PORPOISE*HIROSHI YABU** AND HARUO OGI**Dall's porpoises, Phocoenoides dalli True, 1885, are commonly distributed inthe entire subarctic North Pacific Ocean, Sea of Japan, Sea of Okhotsk andBering Sea. Of the two major color types known to this species, the dalli-type
is widely distributed in the subarctic North Pacific Ocean including Sea ofJapan, Sea of Okhotsk and Bering Sea. Whereas the truei-type is mainly distributed in areas off the Pacific coast of southern Kuril Islands and northernJapan, although some sporadic sightings have been recorded from offshore
western North Pacific and Bering Sea (Nishiwaki, 1967; Kasuya 1978;
Morejohn, 1979; Kasuya and Jones, 1984; Miyazaki, Jones and Beach, 1984).
Makino ( 1948) studied chromosomes of a male P. dalli using traditional
sectioning of testis tissue. Since it was generally accepted in those days thatthe two color morphs represent separate species (Kuroda, '1954; Houck,1976), his study was possibly based on the present "dalli-type" individuals.
The present paper is a preliminary report of a study conducted to further
investigate the chromosomal differences between the two color types of theDall's porpoise.
Materials are ten dalli-types (five males of 97 to 156 cm and five femalesof 68 to 127 cm in body length) and six male truei-types ( 182.1 to 220 cm inbody length) taken in May and June 1984 by the RV Hoyo Maru No. 53 chartered by the Japan Fisheries Agency. Immediately after catching the animals,pieces of gonad, liver and kidney were removed and fixed with acetic alcohol(acetic acid 1 : ethanol 3). These materials were smeared with aceto-ironhaematoxylin-chroral hydrate solution recommended by Wittmann (1965).
The metaphase nuclei available for the chromosome count were obtained
only in the testis from each two males of dalli- and truei-types (Table 1).
In both color types, we found very easily the same chromosome numberof 2n=44 in the spermatogonial metaphase and n=22 in the secondary spermatocyte metaphase (Figs 1 and 2). The chromosome numbers in manydelphinids have been reported as 2n=44 including characteristic X Y
chromosome (Makino, 1948; Wallen and Madin, 1965; Tsuchiya, 1979;* Contribution No. 165 from the Research Institute of the North Pacific Fisheries, Faculty of Fisheries,
Hokkaido University.

** Faculty of Fisheries, Hokkaido Univertsity, Hakodate, Hokkaido, 041 Japan.
Sci. Rep. Whales Res. Inst.,
No. 37, 1986, 99-102

YABUANDOGI

100

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SOME NUMBERS
MENSANDTHEIRCHROMOSESPECI.DATAOFDALLS PORPOITABLEIer
Chromosomenumb
n2nypeort
ColSexdyBohtgnelcm)(Bodythgiew)gk(donetclecotdaetcolecepyt‑illadMale
Male

200
95
164
1
42
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7May18E1。
57
48N 1。
＇46
68E4。
637N 1。
48

44
44

22
22

pey‑ti
門ute
MalMale

216
51.
20

59
123
1

2May1
4
June1

7E1。
50
31N 1。
3829E。
51
31N 1。
41

44
44

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re.Ourobs)
981
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hX Y eluc
esnat
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c
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ed
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gandFiut
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Ygnilbmeser
meosmoorhcdepahs
malrod‑yslmeertex.
)euri(Tlαlnd)i84
91o(nibyMak!‑es,didlphocoennaformisuni
hromosomenumberof2n=44i
Thec,.
町t.IssRe
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7No.3

CHROMOSOMESOFTHEDALL'SPORPOISE

101，、 ．
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， ． − tミρ、，、、、『，. ‑~v··}Jt~バ
島も、 a・一~ J鴫 ー、J

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、~・J

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d0・・‘~ ~Fig.2. Chromosome
softruei‑typeDallsporpoise.x 960
ThesmallchromosomeinA andB isi
ndicate
dbyanarrow.
A. Sperm
atogonialmet
aphase.
B. DiawingofA.
C andD.Secondar
yspermatoqtemetaphase.

phinidsandmonodontidss
tudiedint
hepast(Makino,1948; Wallenand
Madin,1965;Duffield,RidgwayandSpar
kes,1967;Andrews,Dill,MasuiandFis
her,1973;Arnason,1
974;Tsuchi
ya,1979).Int
heaboveg
rou
ps,th
ek
iller
wha
lei
ndelphinidsha
sq
uit
edifferentc
hromosomalmor
pholog
yfromotherspecies(Carr,Singh,MilerandMc
Geer,1966;Horral,Taylo
randTaylor,
1968;Kulu,VeomettandS
parkes,1971).
SinceMakinos(1948)wor
k,noot
hers
t
ud
ie
son t
hec
hromosomeof
Dal
lsp
or
poiseshavebeendone.Ther
efor
e,fur
therc
hr
omosomalstu
dies
mustbeneededtoknowt
hestr
icti
ntr
a‑s
pecificrelati
onshi
pbetweentwo
color‑typesoft
heDallsporpoise.

REFERENCES
ANDRE
WS,R.
C.
,F.
J.DILL,S.MASUIandH.D.F
1s
1E
R,1
973.Thechromosomecomplementoft
hena1whal(Monodonmono
ceros).CanJ.Zoo/.,51(3):349‑353.
ARNASON,U.
,1
974.Comparntivech1omosomes
tudie
sinC
etacca.He
1edi
1as,77(I):1‑36.
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102

YABU AND OGIARNASON, U., 1981. Localization of nucleolar organizing regions in Cetacean karyotypes. Hereditas, 95 (2):269-276.
CARR, D.H., R.P. SINGH, l.R. MILLER and P.L. McGEER, 1966. The chromosome complement of thePacific killer whale (Orcinus rectipinna). Mammal Chromosome Newsletter, 22: 208.
DUFFIELD, D. H., S. H. RIDGWAY and R. S. SPARKES, 1967. Cytogenetic studies of two species of porpoise.
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HoRRALL, J.F., B.K. TAYLOR and K.M. TAYLOR, 1968. Karyotypes of the Pacific killer whale Orcinus area(Linn. 1758), and the Brazilian Tapir, Tapirus terrestris (Gray 1843). Mammal Chromosomes Newsletter,
9: 244-245.
HoucK, W.J., 1976. The taxonomic status of the species of the genus Phocoenoides. FAO of the UN,
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ACMRR/MM/SC/114, pp.1-13.
KASUYA, T., 1978. The life history of Dall's porpoises with special reference to the stock of the Pacificcoast of Japan. Sci. Rep. Whales Res. Inst., 30: 1-63.
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Kuw, D.D., I. VEOMETI and R.S. SPARKES, 1971. Cytogenetic comparison of four species of cetaceans.
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KURODA, N., 1954. On the affinity of the Dall's and True's porpoises. Bull. Yamashina Ornithol. Res. Inst.,
5: 44-46. (in Japanese with English summary).
MAKINO, S., 1948. The chromosomes of Dall's porpoise, Phocoenoides dalli (True), with remarks on thephylogenetic relation of the Cetacea. Chromosoma, 3: 220-231.
MIYAZAKI, N., L.L. JONES and A.R. BEACH, 1984. Some observations on the northwestern Pacific. Sci. Rep.
Whales Res. Inst., 35: 93-105.
MoREJOHN, G. V., 1979. The natural history of Dall's porpoise in the North Pacific Ocean. pp.45-83. In: H. E.
Winn and B. L. Olla (eds), Behavior of marine animals, vol. 3, Prenum Press, New York and London.
438pp.
NISHIWAKI, M., 1967. Distribution and migration of marine mammals in the North Pacific area. Bull. Ocean
Res. Inst., 1: 1-64.
STOCK, A.D., 1981. Chromosomal variation and constitutive hetero chromatin in 3 porpoise species genus
Stenella. Cytogent. Cell Genet., 31 (2): 91-100.
TsuCHIYA, K., 1979. Karyotype of a female Gill's bottle-nosed dolphin Tursiops gilli. Dall. Chromosome Inf Serv.,
26: 18-19.
WALLEN, K.H. and S.H. MADIN, 1965. Comparative chromosome analyses of the bottle-nosed dolphin(Tursiops truncatus) and pilot whale (Globicephala scammonii). American Naturalist, 99(908): 349-354.
WITTMANN, W., 1965. Aceto-iron-haematoxylin-chloral hydrate for chromosome staining. Stain. Tech.,40 (3): 161-164.

Sci. Rep. Whales Res. Inst.,
No. 37, 1986