Heredrras 102: 251-253 (1985)
Conventionally stained and C-banded karyotypes of a female blue
whale
U . ARNASON', H. BELLAMY', P. EYPORSSON', R. LUTLEY', J . SIGURJ6NSSON'
and B. WIDEGREN'
Institute of Genetics, University of Lund, Sweden
108, High Street, Offord Darcey, Huntingdon, Cambs. P E I 8 9RH, England
' Ministry of Fisheries, Reykjavik, Iceland
.I lns~itute
for Experimental Pathology, Keldur, Reykjavik, Iceland
' Marine Reseurch Institute, Reykjavik, Iceland
I
A R N A S O N . U . . BELLAMY. H.. EYP6RSSON. P . . L U r L E Y . R.. SIGURJ6NSSON. J . and WIDEGREN. B.
1985. Conventionally stained and C-banded karyoptypes of a female blue whale. -Hereditas 102: 251-253.
Lund, Sweden. ISSN 0018-0661. Received December 21, 1984
Thc karyotype of a blue whalc was studied in a fibroblast culturc established from a akin hiopsy obtained
from a free swimming animal. The chromosome number was 2n=44. Chromosomal analysis showcd that thc
hiopsy originated from a female specimen. The karyotype conformed with the general 2;=44 cetacean
karyotypes. The C-band pattern had the characteristics observed in other cetacean karyotypes. i.e.. interstitial and terminal C-bands heing more conspicuous than centromeric C-hands.
#/fur Arr?usorr. Institurf of Generics, University of Lrrrtd. Sihegatari 29, s-223 62 ~ u r i d Swrdrn
,
The sample was collected from the research vcsCetacean karyology is now known in considerable
detail, as most of the more easily accessible mate- sel Arni Fridriksson during a fin whale tagging
cruise N E of Iceland. The firing range was about 15
rials have been studied (ARNASON
1974a; DUFFIELD
1977). The blue whale, the largest animal everexist- meters. The sample was preserved in tissue culturc
ing, has been protected for several years and sam- medium until explanted in medium 199, 30 h after
ples of this species have therefore not been available collection. Growth was recorded 2-3 weeks after
at whaling factories. As strandings of living or explantion. Chromosome preparations were made
reasonably fresh specimens of this species are rare, in passage 3 . About 30 % of the cells were diploid,
efforts were made in the summer of 1984 to collect the rest tetraploid. For visualizing C-bands the
skin biopsics from blue whales in the water NE of technique of SUMNEK (1972) was applied. The culIceland. A biopsy was collected from one animal. ture was frozen in passage 4. At the time of freezing
The successful establishment of a fibroblast cell cul- some decline in vitality was observed.
ture showed that this method could be used for collecting samples for chromosomal and biochemical
analysis of protected rare cetacean species.
Results
Materials and methods
The equipment used for the biopsy collection was a
Greener Harpoon Gun with a standard harpoon on
which the original tip was replaced by a biopsy tip,
designed for obtaining skin biopsies of free swimming whalcs. The diameter of samples obtained
using this tip was 11 mm. The final construction of
the tip was obtained after tests at the whaling factory in Hvalfjordur, Iceland.
The chromosome number of diploid cells was
2n=44. Tetraploid cells were 2n=88 with very limited deviation from this number. A conventionally stained karyotype is shown in Fig. l a . The
chromosomes were arranged according to size and
centromeric ratio following a system previously applied on cetacean karyotypes (e.g., ARNASON
1974a).
The karyotype had all the general features of
cetacean 2n=44 karyotypes, characteristically four t
pairs, three large st pairs and one large sm pair. At-
252 i r
AKNASON ET A L
Heredifas 102 (1995)
Fig. l a and b. Karyotype of the blue whale, female. a Conventionally stained karyotype; bar 10 microns. b C-banded
karyotype. Striking C-band polymorphism occurs in several pairs.
Hereditas 102 (I 985)
tachmcnt was frequently observed between the
short arms of the smallest pair of the karyotype,
sm7. This conforms with the presence of one NOR
pair as observed in balenopterid karyotypes and in
cetaceans in general (ARNASON
1981). The X
chromosomes were not positively identified but the
size of the selected pair is similar to that of the X in
most cetaceans.
Fig. I b shows a C-banded karyotype of the same
specimen. The C-bands of the blue whale are conspicuous. The localization of the C-bands is primarily interstitial, centromeric C-bands are sparse. Terminal C-bands were less prominent than in other
balenopterids studied. C-band heteromorphism
was seen in Feveral pairs, notably in the interstitial
bands in the long arm, q , of s m l , in the terminal region of sm3q, in the terminal C-bands in st2p and
st3p and in the intersitital band in t3q.
Discussion
KARYOTYPES OF A FEMALE BLUE WHALE
253
studied using banding analysis. A particular evolutionary pattern based on C-band distribution in
genus Balaenoptera is not evident.
Among the four karyotypes, that of the fin whale
appears to be the most extreme with respect to accumulation of C-heterochromatin. The amount of
C-heterochromatin in the blue whale is distinctly
less than in the fin whale and also appears to be
more limited than in the other two balenopterids,
the minke and sei whales. The most characteristic
C-band feature of the blue whale when compared
with the other balenopterids is the centromeric Cband in sm3 and the interstitial band in sm5q. Cbands in these positions have not been observed in
other balenopterids.
The possibility of obtaining skin biopsies from
protected cetacean species opens new opportunities
for various other studies besides karyological
analysis. Thus, cell cultures originating from skin
biopsies can be used for molecular biological
analysis and even for population studies, provided a
sufficient number of samples can be collected. It
should, however, be borne in mind that the cost of
sampling at higher latitudes is very high and therefore the sampling needs to be coordinated with
marine research in other fields.
The karyological uniformity of cetaceans and
marine mammals in general has been a subject of
discussion in several papers (ARNASON
1972, 1974a,
1974h, 1982). Among the cetaceans the great
majority of all species so far studied have 2n=44 and Acknowledgements. - The authors express their gratitude to Mr
strikingly similar karyotypes (AKNASON
1974a; DUF- Kristofer Gunnarsson for his expert craftsmanship in making the
biopsy tip used. Mr Stefnir Helgason and Mr Elias Helgason on the
riFi.i) 1977). The general 2n=44 karyotype has thus
fishing boat Mar of Bakkafjordur transported the biopsy to
been preserved in both odontocetes and mysticetes, Kopasker. To them and to the flight crews who carried the samples
two lineages which separated more than 40 million to Reykjavik we express our sincere thanks. Our thanks are also
years ago. These similarities became apparent after due to Dr. Gudmundur Petursson. Director. Institute for Experistudies on the karyotype of the fin whale, the first mental Pathology, Keldur, Iceland, for laboratory facilities.
mysticete analyzed using long term tissue culture
(ARNASON
1969). C-band studies of several cetacean Literature cited
species (ARNASON
1974a; DUFFIELD
1977) showed ARNASON, U. 1969. The karyotype of the fin whale. - Ifrrediras
that C-bands were conspicuous in the cetacean
62: 273-23-284
karyotypes and that their pattern of localization was ARNASON.U. IY72. The role of chromosomal rearrangement in
mammalian speciation with special reference to Cetacea and Pinsimilar among the species studied. The C-bands
nipedia. -Hereditas 70: 113-1 I X
thus occurred primarily in interstitial and terminal ARNASON.
0.1974a. Comparative chromosome studies in
chromosome positions while centromeric C-bands
Cetacea. -Hereditas 7 7 1-36
ARNASON,0 . 1974b. Comparative chromosome studies in Pinwere less prominent.
nipedia. - Herediras 75: 179-226
Durtw.il (1977) reported a C-banded karyotype
ARNASON,U, 1981. Localization of nucicolar organizing regions
of a male blue whale. The conformity between her
in cetacean karyotypes. - Herediras 95: 269-275
observation and the present material is evident al- ARNASON,0 . 1982. Karyotype stability in marine mammals. Cytogener. Cell Gener. 33: 274-276
though the original karyotype was not used for comDUFFIELD, D. A. 1977. Phylokaryotypic evaluation of the
parison.
Cetacea. - P1i.D. Thesis, Univ. of California, t o s Angeks
Among the balenopterids. four species, the S U M N E R , A. T. 1972. A simple technique for demonstrating cenminke, sei, fin and blue whales, have now been
tromeric heterochromatin. - Exp. Cell Res. 75: 304-306