SC/D06/J8

A BRIEF REVIEW OF THE GENETIC STUDIES ON DWARF
MINKE WHALE BASED ON JARPA SAMPLES
Luis A. Pastene
Institute of Cetacean Research, Toyomi-cho 4-5, Chuo-ku, Tokyo 104-0055, Japan

ABSTRACT
Prior to the JARPA surveys ‘dwarf’ minke whales were only believed to be found between 7-41°S. However the
locality of the JARPA catches in Areas IV and V was mainly between 55-62°S (one animal was caught at 65°S),
showing that the ‘dwarf’ minke whale is found much further south than shown by the previous data. A total of 16‘dwarf’ minke whales were sampled by JARPA and these animals were examined genetically with the purpose toinvestigate their relationship to the southern ‘ordinary’ minke whale and to minke whales in the Northern
Hemisphere. Early studies showed that the degree of mtDNA divergence between both southern minke whales
was large and similar to that found between southern ‘ordinary’ minke whale and Northern Hemisphere minke
whales. Phylogenetic analyses showed that the ‘dwarf’ minke whale was more closely related to Northern
Hemisphere minke whales. In 1993 the Scientific Committee recommended the inclusion of the ‘dwarf’ minke
whale in the Schedule, so that catch limits for Antarctic minke whales recognise the distinction between the twosouthern minke whales. The genetic analysis conducted using JARPA samples of the southern ‘ordinary’ and‘dwarf’ minke whales assisted greatly to the taxonomic review of minke whale conducted by Rice (1998), which
confirmed the existence of two species, the larger, Antarctic minke whale Balaenoptera bonaerensis confined to
the Southern Hemisphere, and the smaller, common minke whale B. acutorostrata distributed in bothhemispheres. ‘Dwarf’ minke whale is sympatric to the Antarctic minke whale but in the review by Rice (1998) it
was considered an unnamed sub-species of the common minke whale. Recent mtDNA analyses suggest that the
sub-specific classification of common minke whales requires further consideration. Recent studies have showedthat the ‘dwarf’ minke whales are genetically structured in the Southern Hemisphere.
INTRODUCTION
The first documented study that demonstrated marked morphological differences between 'diminutive' or 'dwarf'and ‘ordinary’ minke whales in the Southern Hemisphere was based on samples from South Africa (Best, 1985).
Subsequently, Arnold et al. (1987) presented evidence for morphological differentiation along the Australiancoast. Those authors described several morphological differences between the ‘dwarf’ and ‘ordinary’ minke
whales in the Southern Hemisphere of which the most distinctive concerned the color of the body and baleen
plates and the shape of the skull. The ‘dwarf’ minke whale has a predominantly light baleen series and a whitebase to the flippers, whilst the ‘ordinary’ minke whale has asymmetrically colored baleen plates. Although theflippers of the ‘ordinary’ minke whale may have one or two tones of gray, they are never white at the base, as inthe ‘dwarf’ minke whale. In the ‘dwarf’ minke whale, the dark pigmentation in the neck region extends onto theventral grooves whereas in the ‘ordinary’ minke whale it does not occur below eye level. The ‘dwarf’ minke
whale also has anteriorly convex nasal bones as opposed to the concave nasal bones in the ‘ordinary’ minke
whale. In most of these morphological characteristics the ‘dwarf’ minke whale more closely resembles Northern
Hemisphere minke whales.
Kato and Fujise (2000) reported the morphology, growth and life history of ‘dwarf’ minke whales based on 16
animals sampled by JARPA in the Antarctic. Results of their analysis confirmed several of the morphologicaland morphometric characters reported previously. They reported the mean body length at physical maturity at
7.0m for females and 6.6m for males. According to this source the apparent pregnancy rate among mature
females was 1.0 and the conception is highly concentrated in mid-winter. These authors also reported that the age
and length at sexual maturity in females was 7-10 years and 6.0-6.5m, respectively.
The ‘dwarf’ minke whale has been identified from the Brazilian minke whale catches (da Rocha and Braga,1982). Baker (1983) identified and illustrated this whale among minke whales stranded on the New Zealandcoast. Zerbini et al. (1996) reviewed the records on ‘dwarf’ minke whale in Brazil, and their results suggest that
this whale could be relatively common in that region. More recently Acevedo et al. (in press) reported thestranding of three ‘dwarf’ minke whales in Navarino Island, in the southern tip of the America continent.

1

Prior to the JARPA in the Antarctic (1987/88) the ‘dwarf’ minke whale was only believed to be found between
7-41°S (Best, 1985); no ‘dwarf’ minke whales had been identified in past commercial catches near the ice edge.
The ‘dwarf’ minke whale was reported for Antarctic waters for the first time, on the basis of catches conductedduring earlier JARPA surveys (Kato et al., 1989; 1990; Fujise et al., 1990; 1993; Kasamatsu et al., 1993).
Distribution of the JARPA catches in Areas IV and V was mainly between 55º-62ºS (one individual was caught
at 65ºS), showing that the ‘dwarf’ minke whale is found much further south than shown by the previous catchdata.
The objective of this paper is to summarize the genetic studies conducted on ‘dwarf’ minke whales and theimplication for their taxonomy, management and conservation.
GENETIC STUDIES
Allozyme analysis
The first genetic study was carried out by Wada (1983) who analysed a single sample from a South Africa
animal that presented similar morphological characteristics to the ‘dwarf’ minke whale. His allozyme study,
however, found no significant differences between this sample and those from the southern ‘ordinary’ minke
whale.
Mitochondrial DNA RFLP analysis
Wada et al. (1991) examined genetic diversity in minke whales from the North Pacific and the Antarctic using
restriction fragment length polymorphism (RFLP) analysis of the whole mtDNA genome. The Antarctic sample
included a single individual of the ‘dwarf’ minke whale, sampled during the first JARPA feasibility study in
Area IV in the austral summer 1987/88 (Kato et al., 1989). They digested mtDNAs with 14 six-base sequence
recognition restriction enzymes and, based on the composite digestion patterns of a total 142 minke whales, 19
haplotypes were resolved. There was no shared haplotype among North Pacific, southern ‘ordinary’ and ‘dwarf’
minke whales. Furthermore an UPGMA-derived dendrogram based on genetic distances, showed that the ‘dwarf’
minke whale and minke whales from the North Pacific are more similar to each other than they are to thesouthern ‘ordinary’ minke whale.
It should be noted that the allozyme study of Wada (1983) and the mtDNA study of Wada et al. (1991) werebased on a single ‘dwarf’ minke whale, which generated contradictory results. Using a larger number of samplesof the ‘dwarf’ minke whale, Pastene et al. (1994) examined the differentiation of mtDNA between southern‘ordinary’ and ‘dwarf’ minke whales. These authors conducted a RFLP analysis of the whole mtDNA moleculeusing 11 samples of the ‘dwarf’ and 18 of the ‘ordinary’ minke whales taken during JARPA surveys. MtDNAs
extracted from liver samples were digested with 11 six-base restriction enzymes revealing a total of thirteen
mtDNA haplotypes in the total sample. There were no shared haplotypes between the two southern minke whales.
Three haplotypes were found in the ‘dwarf’ and ten in the ‘ordinary’ minke whale. The larger number of samplesof the ‘dwarf’ minke whale enabled the degree of genetic variation within this form to be investigated. The index
of nucleotide diversity (Nei and Li, 1979) was higher in the ‘ordinary’ minke whale than in the ‘dwarf’ minke
whale. The degree of genetic diversity within each of these minke whales was similar or lower to that of othercetaceans (Pastene et al., 1994). The net genetic distance between the two southern minke whales was estimatedat 0.0524. A comparison with published information for other species revealed that the genetic distance between
the ‘dwarf’ and ‘ordinary’ minke whales was larger than that for some recognised species of land and marine
mammals.
Using RFLP data from Wada et al. (1991) for the North Pacific minke whale, Pastene et al. (1994) studied thegenetic relationships among North Pacific, Antarctic ‘ordinary’ and ‘dwarf’ minke whales. There was no shared
haplotypes among them (two were discriminated in the ‘dwarf’, three in the North Pacific and eight in thesouthern ‘ordinary’ minke whales). An UPGMA-derived dendrogram of mtDNA haplotypes based on genetic
distances (Figure 1), confirmed that the dwarf and the North Pacific minke whales are more similar to each otherthan they are to the Antarctic ‘ordinary’ minke whale. Then the work by Pastene et al. (1994), which was basedon a larger number of samples of the ‘dwarf’ minke whale, supported the previous finding of Wada et al. (1991).
Mitochondrial DNA control region sequencing
Hori et al. (1994) and Pastene et al. (1996) investigated the phylogenetic relationships of ‘dwarf’ minke whalewith North Pacific, North Atlantic and Antarctic ‘ordinary’ minke whales. Antarctic ‘dwarf’ and ‘ordinary’minke whales samples were taken during JARPA surveys. In the analysis, published sequence data of the North
Atlantic minke whale were used. The method used was the amplification by the polymerase chain reaction (PCR)2

of the non-coding control region of mtDNA followed by sequencing of 343 base-pairs. A neighbor-joining-based
phylogenetic tree (Saitou and Nei, 1987) of 56 unique sequences (Figure 2) showed that southern ‘dwarf’,southern ‘ordinary’, North Pacific and North Atlantic minke whales are separated from each other, suggesting
independent genetic populations. The tree also showed that ‘dwarf’ minke whales are more closely related to
Northern Hemisphere minke whales than to the southern ‘ordinary’ minke whale. The ‘dwarf’ minke whale isclearly remote from the southern ‘ordinary’ minke whale despite the overlap in their distribution and apparent
ecological niche.
Table 1 shows the nucleotide diversity and the net genetic distances among minke whales from different ocean
basins based on the Kimura's two parameters method (Kimura, 1980). The larger distances are obtained in the
pairwise comparisons involving the southern ‘ordinary’ minke whale. These values range from 0.082 to 0.088.
The values among the other three minke whales range from 0.015 (comparison between Antarctic ‘dwarf’ andNorth Atlantic minke whales) to 0.025 (comparison between Antarctic ‘dwarf’ and North Pacific minke whales).
TAXONOMIC STATUS OF MINKE WHALES
Some authors (Omura, 1975; Rice, 1977) had proposed sub-specific status for the North Atlantic (Balaenoptera
acutorostrata acutorostrata), North Pacific (B. a. davidsoni) and Antarctic ‘ordinary’ minke whales (B. a.
bonaerensis). Arnason et al. (1993) suggested that given the large genetic distances between the southern‘ordinary’ minke whale and minke whales from other oceanic basins the former should be given full species
status Balaenoptera bonaerensis.
Rice (1998) reviewed both morphological (e.g., Omura, 1975; Best, 1985; Arnold et al., 1987) and genetic(e.g., Pastene et al. 1994; Wada et al. 1991; Arnason et al., 1993) data collected from extant minke whale
populations and divided minke whales into two species; the larger Antarctic minke whale (B. bonaerensis),which is restricted only to the Southern Hemisphere, and the cosmopolitan common minke whale (B.
acutorostrata). Furthermore he divided the common minke whale into three sub-species: North Atlantic B. a.
acutorostrata, North Pacific, B.a. scammoni and Southern Hemisphere (‘dwarf’), B. a. subsp. The sub-specificclassification is controversial if we consider the phylogeny of common minke whales from different ocean basins.
Recent genetic studies have shown a paraphyletic relationship between North Atlantic and southern ‘dwarf’
minke whales (see next section). The sub-specific classification of common minke whale should be reconsidered in the light of results of additional genetic studies of minke whales based on nuclear DNA, and thecompletion of some on-going comparative morphological and morphometric analyses.
RECENT GENETIC STUDIES AND FUTURE WORK
Acevedo et al. (2005) studied the phylogenetic relationship of three ‘dwarf’ minke whales stranded in Navarino
Island in the southern tip of the American continent, with ‘dwarf’ minke whales from the Antarctic (Areas IV
and V, n=15) and Brazil (n=8), North Atlantic common minke whale, North Pacific common minke whale andAntarctic minke whale. A neighbor-joining-based tree of mtDNA control region sequences showed that, of three
Brazilian haplotypes, one clustered with the Antarctic ‘dwarf’ minke whale clade and two with the North
Atlantic common minke whale clade (Figure 3). The Chilean ‘dwarf’ minke whales were phylogeneticallyrelated to ‘dwarf’ minke whales from Brazil. No shared haplotypes were found between ‘dwarf’ minke whales
from the Antarctic and Brazil, and significant level of genetic divergence (as measured by Kst) was foundbetween them (data not shown).
A large collection of genetic samples from the ‘dwarf’ minke whale are necessary to further understand their
genetic structure in the Southern Hemisphere and their relationship to other minke whales. Nuclear DNA
analyses are necessary to complement the results found by the mtDNA analyses. This additional genetic analysis
and the completion of on-going morphological and morphometric work are also important to clarify thetaxonomy of the common minke whale.
MANAGEMENT IMPLICATIONS
On the basis on the morphological differences documented by Best (1985) and Arnold et al. (1987) and genetic
differences (Wada et al., 1991), the SC recognised the existence of two southern minke whales and agreed thatthe two minke whales in the Southern Hemisphere should definitely be considered separately for management
purposes (IWC, 1991). In 1993, after examining the genetic information given by Pastene et al. (1994), the SC
recommended the inclusion of the ‘dwarf’ minke whale in the Schedule, so that catch limits for Antarctic minke
whales recognise the distinction between the two southern minke whales (IWC, 1994).

3

As mentioned above, the Committee had recommended the management of the two southern minke whale
species separately. This had had practical implications for population assessment studies, and both Antarctic and‘dwarf’ minke whales are recorded separately in JARPA and SOWER sighting cruise surveys. Experienced
researcher and crew members involved in these surveys in the Antarctic indicated that there are distinct
differences that can be detected at sea, e.g. body colouration, the white patch on the base of flipper and theswimming pattern. Some of these probably require good weather and observation conditions to be identified.
REFERENCES
Acevedo, J., Aguayo-Lobo, A., Acuna, P., Goto, M., Zerbini, A. and Pastene, L.A. 2005. First record of thedwarf minke whale Balaenoptera acutorostrata in Chilean waters. Paper SC/57/IA10 presented to the
IWC Scientific Committee. May 2005 (unpublished). 8pp.
Acevedo, J., Aguayo-Lobo, A., Acuna, P. and Pastene, L.A. (in press). First record of the dwarf minke whale
Balaenoptera acutorostrata in Chilean waters. Journal Cetacean Res Manage (in press).
Arnold, P., Marsh, H. and Heinsohn, G. 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. Scientific
Reports of the Whales Research Institute Tokyo 38:1-46.
Baker, A.N. (ed.). 1983. Whales and dolphins of New Zealand and Australia. An Identification Guide. Victoria
University Press. 133pp
Best, P.B. 1985. External characters of southern minke whales and the existence of a diminutive form. Scientific
Reports of the Whales Research Institute Tokyo 36:1-33.
da Rocha, J.M. and Braga, N.M.A. 1982. Brazil Progress report on cetacean research, June 1980 to May 1981.
Rep int. Whal. Commn 32:155-9.
Fujise, Y., Zenitani, R., Saino, S., Itoh, S., Kawasaki, M., Matsuoka, K. and Tamura, T. 1993. Cruise report ofthe 1992/93 Japanese research under the special permit for Southern Hemisphere minke whales. Paper
SC/45/SHBa12 presented to the IWC Scientific Committee, April 1993 (unpublished). 39pp.
Government of Japan. 1993. The 1993/94 research plan of whale resources in the Antarctic. Paper
SC/45/SHBa10 presented to the IWC Scientific Committee, April 1993 (unpublished). 6pp.
Hori, H., Bessho, Y., Kawabata, R., Watanabe, I., Koga, A. and Pastene, L.A. 1994. World-wide population
structure of minke whales deduced from mitochondrial DNA control region sequences. Paper
SC/46/SH14 presented to the IWC Scientific Committee, May 1994 (unpublished). 11pp.
International Whaling Commission. 1991. Report of the Scientific Committee. Rep. int. Whal. Commn 41:51-89.
International Whaling Commission. 1994. Report of the Scientific Committee. Rep. int. Whal. Commn 44:41-73.
Kasamatsu F, Yamamoto Y, Zenitani R et al. 1993. Report of the 1990/91 southern minke whale research cruise
under scientific permit in Area V. Report of the International Whaling Commission 43:505-522.
Kato, H. and Fujise, Y. 2000. Dwarf minke whales; morphology, growth and life history with some analyses onmorphometric variation among the different forms and regions. Paper SC/52/OS3 presented to the
Scientific Committee. June 2000 (unpublished). 30pp.
Kato, H., Hiroyama, H., Fujise, Y. and Ono, K. 1989. Preliminary report of the 1987/88 Japanese feasibility
study of the special permit proposal for Southern Hemisphere minke whales. Rep. int. Whal. Commn 39:
235-248.
Kato, H., Fujise, Y., Yoshida, H., Nakagawa, S., Ishida, M. and Tanifuji, S. 1990. Cruise report and preliminary
analysis of the 1988/89 Japanese feasibility study of the special permit proposal for southernhemisphere minke whales. Rep. int. Whal. Commn 40: 289-300.

4

Kimura, M. 1980. A simple method for estimating evolutionary rates of base substitutions through comparative
studies of nucleotide sequences. J Mol Evol 16:111-120.
Nei, M, and Li, W.H. 1979. Mathematical model for studying genetic variation in terms of restriction
endonucleases. Proceedings of the National Academy of Science, USA 76:5269-5273.
Omura, H. 1975. Osteological study of the minke whale from the Antarctic. Scientific Reports of the Whales
Research Institute 27:1-36.
Pastene, L.A., Fujise, Y. and Numachi, K. 1994. Differentiation of mitochondrial DNA between ordinary anddwarf forms of minke whale. Report of the International Whaling Commission 44:277-281.
Pastene, L.A., Hori, H., Watanabe, K., Bessho, Y. and Goto, M. 1996. Phylogenetic relationships in the minke
whale world-wide as revealed by two independent analyses of mitochondrial DNA. 7th Working
Meeting of Specialists in Aquatic Mammals of South America, 22-25 October 1996, Viña del Mar,
Chile. Supplement p.53.
Rice, D.W. 1977. A list of the marine mammals of the world. NOAA Tech. Rep. 711:1-15.
Rice, D.W. 1998. Marine Mammals of the World. Systematic and Distribution. Marine Mammal Science(Special Issue).
Saitou, N. and Nei, M. 1987. The neighbor-joining method: a new method for reconstructing phylogenetic tree.
Mol. Biol. Evol. 4(4):406-25.
Wada, S. 1983. Genetic structure and taxonomic status of minke whales in the coastal waters of Japan. Rep. int.
Whal. Commn 33:361-3.
Wada, S., Kobayashi, T. and Numachi, K. 1991. Genetic variability and differentiation of mitochondrial
DNA in minke whales. Report of the International Whaling Commission Special Issue 13:203-215.
Zerbini, A.N., Secchi, E.R., Siciliano, S. and Simoes-Lopes, P.C. 1996. The dwarf form of the minke whale,
Balaenoptera acutorostrata Lacepede, 1804, in Brazil. Rep. int. Whal. Commn 46:333- 340.

Table 1: Nucleotide diversity (diagonal) and net genetic distances, derived from mtDNA control region
sequence data. AO= southern ‘ordinary’ minke whale, AD= southern dwarf minke whale, NP= North Pacificminke whale, NA= North Atlantic minke whale (from Pastene et al., 1996).

AO
AD
NP
NA

AO
0.025

AD
0.086
0.012

NP
0.082
0.025
0.014

NA
0.088
0.015
0.020
0.007

5

Figure 1: UPGM-derived dendrogram of 13 minke whale RFLP-derived mtDNA haplotype, based on sequence
divergence among them (from Pastene et al., 1994).

6

Figure 2: Neighbor-joining-derived tree of 56 unique mtDNA control region sequences in the minke whale AO=
southern ‘ordinary’ minke whale, AD= southern dwarf minke whale, NP= North Pacific minke whale, NA=
North Atlantic minke whale (from Pastene et al., 1996).

.

7

Figure 3: Neighbor-joining-derived tree of minke whale mtDNA control region sequences. Bb= B. bonaerensis;
BaAD= B. acutorostrata, Antarctic dwarf; BaNP= B. acutorostrata North Pacific; BaNA= B. acutorostrata
North Atlantic; BaBD= B. acutorostrata Brazil dwarf; UCM= B. acutorostrata Chile. Arrows shows the positionof the three Chilean dwarf minke whale haplotypes. Brazilian dwarf haplotypes are indicated in squares. Figures
show bootstrap values (in 1,000 simulations) (from Acevedo et al., 2005).

8