B CHROMOSOME NUMBER VARIABILITY IN

THE KOREAN FIELD MOUSE APODEMUS

PENINSULAE (RODENTIA) FROM THE RUSSIAN FAR

EAST

G.V. Roslik, I.V. Kartavtseva Institute of Biology and Soil Science of Far-Eastern

Branch of Russian Academy of Sciences, Vladivostok, Russia

2

Apodemus peninsulae Thomas, 1906 is a polytypic species which widely distributed from East Siberia and North Mongolia, China to the Russian Far East,

Korea and Japan (Hokkaido)

- our data

- literature data

Photo by I. Kartavtseva

33

The standard chromosome setThe standard chromosome setof the Korean field mouse, of the Korean field mouse, Apodemus peninsulaeApodemus peninsulae contains contains 48 acrocentric chromosomes48 acrocentric chromosomes and supernumerary chromosomes varying in number from 0 to 30 - in Siberia and from 0 to 7 in the Russian Far East.The B chromosomes (Bs) also had variations in size (from big to small) and in morphology – from macro to micro Bs (more frequently meta-, submetacentrics and micro Bs and rare subtelo-, acrocentrics and mini Bs)

44

The levels of B chromosome’s The levels of B chromosome’s system variability in system variability in A. peninsulae:A. peninsulae:

• intrapopulational,intrapopulational,

• Interpopulational,Interpopulational,

• tissue, or individual (mosaicism),tissue, or individual (mosaicism),

• and variability of B’s differential staining. and variability of B’s differential staining.

55

THE AIM OF THE WORK WASTHE AIM OF THE WORK WAS::

• To study mosaicism on B To study mosaicism on B chromosome of the Korean chromosome of the Korean

field mouse field mouse Apodemus Apodemus peninsulae peninsulae fromfrom the Russian the Russian

Far EastFar East

66

MATERIAL OF THE MATERIAL OF THE STUDY STUDY OFOFApodemus peninsulaeApodemus peninsulae Thomas Thomas 1906 1906

• The intra individual The intra individual mosaicism of Bs was study mosaicism of Bs was study in 355 animals collected at in 355 animals collected at 41 continental natural 41 continental natural localities of the Russian Far localities of the Russian Far East. East.

• There were specimens: There were specimens: from Magadan, Amur, from Magadan, Amur, Jewish and Khabarovsk Jewish and Khabarovsk Regions (n=87),Regions (n=87),

• and also from Primorskiy and also from Primorskiy Region (n=268).Region (n=268).

DISTINGUISHING OF MOSAICSDISTINGUISHING OF MOSAICSMosaicism was evaluated on the basis of the Mosaicism was evaluated on the basis of the number of cellular clones. number of cellular clones. Mosaics had two and Mosaics had two and more clones.more clones.Cellular clone - this is group of cells with the Cellular clone - this is group of cells with the definite number of chromosomes.definite number of chromosomes.

Cellular clones are isolated employing procedure Cellular clones are isolated employing procedure D.K. Belyayev with co-authors (1974);D.K. Belyayev with co-authors (1974); and number and number of cells analysed was determined according E.B. of cells analysed was determined according E.B. Hook (1977).Hook (1977).CClones are determined lones are determined aas the groups of the cells, s the groups of the cells, when the hypowhen the hypoploidploid class composes 10% and class composes 10% and more, and hypermore, and hyperploidploid - more or is equal to 5% - more or is equal to 5% (from the modal number of chromosomes)(from the modal number of chromosomes)..

88

Frequency of intra individual Frequency of intra individual mosaicism of Bsmosaicism of Bs

• The wood mice have very frequentThe wood mice have very frequent occurrence of B chromosomes. It was found occurrence of B chromosomes. It was found that 312 that 312 (87.9 %)(87.9 %) animals possessed animals possessed B B chromosomeschromosomes. .

• 219 219 (61.7 %)(61.7 %) were were mosaicsmosaics with from two to with from two to five cellular clones andfive cellular clones and

• only 136 (only 136 (38,3%)38,3%) mice had mice had stable stable karyotypes.karyotypes.

99

MOSAICISM IN DIRRERENT MOSAICISM IN DIRRERENT POPULATIONS of POPULATIONS of A. peninsulae: A. peninsulae:

a–Khabarovsk Reg., b – Primorskiy Reg.a–Khabarovsk Reg., b – Primorskiy Reg.Evoron Lake -total (2001, 2002),

n=16 19%

6%

75%stable with Bs stable wihtout Bs mosaics

MagadanMagadan RegionRegion

AmurAmur RegionRegion

JewishJewish RegionRegion

Khabarovsk RegionsKhabarovsk Regions

Primorskiy RegionPrimorskiy Region

Borisovskoye plateau, n=813%

25%62%

stable with Bs stable wihtout Bs mosaics

Evoron Lake -total (2001, 2002), n=16 19%

6%

75%stable with Bs stable wihtout Bs mosaics

Borisovskoye plateau, n=813%

25%62%

stable with Bs stable wihtout Bs mosaics

Evoron Lake -total (2001, 2002), n=16 19%

6%

75%stable with Bs stable wihtout Bs mosaics

1010

MOSAICISM AT THE SAME MOSAICISM AT THE SAME POPULATION IN DIFFERENT YEARSPOPULATION IN DIFFERENT YEARS

Ussuriyskiy Res.-1996, n=26

57%14%

29%

stable with Bs stable without Bs mosaics

Ussuriyskiy Res. -1990, n=1030%

30%

40%

stable with Bs stable without Bs mosaics

Ussuriyskiy Res. - total (1987, 1989,1990, 1992,1995-1999), n=74

40%

19%

41%

stable with Bs stable without Bs mosaics

Ussuriyskiy Res.- 1999, n=138%

46%

46%

stable with Bs stable without Bs mosaics

1111

THE OCCURRENCE OF MOSAICSTHE OCCURRENCE OF MOSAICSMagadan, Jewish and Amur

Regions, n=200

30

70

without Bs stable,with Bs mosaics

Khabarovsk Region, n=67

22,4

16,4

61,2

without Bs stable,with Bs mosaics

Primorsky Region, n=268

10,4

28,4

61,2

without Bs stable,with Bs mosaics

The Russian Far East, total n=355

12,1

26,261,7

without Bs stable,with Bs mosaics

1212

SPECTRA OF Bs NUMBER SPECTRA OF Bs NUMBER VARIATIONVARIATION

01020304050607080

0 1 2 3 4Number of B chromosomes

Portio

n of sp

ecime

ns, %

MR-JR (n = 6) KHR (n = 26) PR (n = 104)

0

5

10

15

20

25

0-1 0-2 0-3 0-4 0-5 1-2 1-3 1-4 1-5 2-3 2-4 2-5 3-4 3-5 3-6 4-5 4-7 5-7Spectra of B chromosome variation

Po

rtio

n o

f sp

ec

ime

ns

, %

PR (n = 164) AR-JR (n = 14) KHR (n = 41)

MR – Magadan Region, AR – Amur Region,JR – Jewish Region, KHR – Khabarovsk Region,PR – Primorskiy Region;n - number of specimens.

Stable

Mosaics

1313

METAPHASES WITH DIFFERENT METAPHASES WITH DIFFERENT В В CHROMOSOMESCHROMOSOMES

m

m

m

m

ST

ST

2M+2ST (large and small) – Primorskiy Region (Nezhino vil.)

2M (middle and small) – Primorskiy Region (Ussuriyskiy Reserve)

M

M

MM

2n=48+4Bs

2n=48+2Bs

14

SIZE AND MORPHOLOGY TYPES OF B CHROMOSOMES (Bs)

M M

ST

M

M

M

M

M

M

M M

SMM-mi

M-mi

Macro Bs: M –metacentrics, SM- submetacentic, ST-subtelocentric and

mi - mini B chromosomes, seems as metacentrics (M).

2n=48+7Bs 2n=48+7Bs

Evoron Lake

Borisovskoye plateau

1515

TYPES OF B CHROMOSOMESTYPES OF B CHROMOSOMES

0

20

40

60

80

100

120

LargeM,SM,ST

MiddleM,SM,ST

SmallM,SM,ST

mini Small A micro

Types of B chromosomes

Porti

on o

f soe

cim

ens,

%

Magadan Reg.Amur Reg.Jewish Reg.Khabarovsk Reg.Primorsky Reg.

n=23(6,5%)

n=5(1,4%)n=24 (6,8%) n=33 (9,3%)

n=164(46,2%)

n=264(74,4 %)

Large M,SM,ST Middle M,SM,STSmall M,SM,ST miniSmall A micro

1616

THE B CHROMOSOME THE B CHROMOSOME SYSTEMSYSTEM

• There There 78 variants78 variants of the B chromosome system of the B chromosome system have been first found out, distinguished by the have been first found out, distinguished by the number, size and morphology of B-chromosomes. number, size and morphology of B-chromosomes.

• We described 22 variants in animals with stable We described 22 variants in animals with stable karyotype (n = 136). The greatest variety of the karyotype (n = 136). The greatest variety of the variants (up 76) has been found in mosaics variants (up 76) has been found in mosaics divided into two subgroups - with one and with divided into two subgroups - with one and with two or more prevailing variants. In the first two or more prevailing variants. In the first subgroup (n = 90) 68 and in another subgroup (n subgroup (n = 90) 68 and in another subgroup (n = 129) - 104 combinations of the variants have = 129) - 104 combinations of the variants have been revealed. been revealed.

• The combinations of the variants and their The combinations of the variants and their percent correlations percent correlations were often uniquewere often unique. .

1717

DISTRIBUTIONDISTRIBUTION OF DEFINITE OF DEFINITE VARIANTS OF THE B CHROMOSOME VARIANTS OF THE B CHROMOSOME SYSTEMSYSTEM

Stable, n=136

38(28%) 43

(31%)

22(16%)8 (6%)

16(12%)

9(7%)

B=0B=1M,smallB=1M,middleB=2M,smallB=1M,middle+1M,smallother

Mosaics, n=219

76(35%)

33(15%)

44 (20%)

20(9%)

31 (14%)15 (7%)

B=0B=1M,smallB=1M,middleB=2M,smallB=1M,middle+1M,smallothera b

As rule, sector “Other” includes unique variants of the B chromosome system

1818

THE OCCURRENCE VARIANTS OF THE OCCURRENCE VARIANTS OF THE B CHROMOSOME SYSTEMTHE B CHROMOSOME SYSTEM

• The optimum chromosome number (50) has been The optimum chromosome number (50) has been established as in animals with stable karyotype (a) established as in animals with stable karyotype (a) and in mosaics (b)and in mosaics (b)

• Variants = size and morphology variants.Variants = size and morphology variants.

0

1

2

34

5

6

7

48 49 50 51 52Chromosome number

Nu

mb

er

of

va

ria

nts

0

5

10

1520

25

30

35

Po

rtio

n o

f a

nim

als

, %

Number of variantsPortion of animals

0

5

10

15

20

25

48 49 50 51 52 53 54 55Chromosome number

Num

ber o

f var

iant

s

0

5

10

15

20

25

30

35

Por

tion

of a

nim

als,

%

Number of variants Portion of animals

a b

MosaicsStable

1919

CONCLUSIONS:CONCLUSIONS:

• The predominance of mosaics have been The predominance of mosaics have been revealed in populations of the Russian Far revealed in populations of the Russian Far East. East.

• The percentage of mosaics are various The percentage of mosaics are various both in both in the different populations and between the the different populations and between the samples from one population, but practically samples from one population, but practically no differences in the united populations of no differences in the united populations of three geographic regions.three geographic regions.

2020

CONCLUSIONS:CONCLUSIONS:• The spectra of B chromosome variability The spectra of B chromosome variability

were wider in mosaics (from 0 to 7) in were wider in mosaics (from 0 to 7) in comparison with animals with stable comparison with animals with stable karyotype (from 0 to 4).karyotype (from 0 to 4).

• The optimum chromosome number (50) The optimum chromosome number (50) has been established in mosaics as well in has been established in mosaics as well in animals with stable karyotype.animals with stable karyotype.

2121

CONCLUSIONS:CONCLUSIONS:

• The adaptive role of the low number of B The adaptive role of the low number of B chromosomes (1-2) is assumed and the B chromosomes (1-2) is assumed and the B chromosome system seems not to be chromosome system seems not to be balanced in the species in whole. balanced in the species in whole.

• The distribution of mice with the similar The distribution of mice with the similar variants of the B chromosome system in variants of the B chromosome system in the Far-Eastern populations of species the Far-Eastern populations of species seems to be of the chaotic nature.seems to be of the chaotic nature.

2222

2323

THE OCCURRENCE OF MOSAICS THE OCCURRENCE OF MOSAICS

Khabarovsk Region, n=67

22,4

16,4

61,2

without Bs stable,with Bs mosaics

Magadan, Jewish and Amur Regions, n=20

030

70

without Bs stable,with Bs mosaics

Primorsky Region, n=268

10,4

28,4

61,2

without Bs stable,with Bs mosaics

The Russian Far East, total n=355

12,1

26,261,7

without Bs stable,with Bs mosaics

2424

B-CHROMOSOME B-CHROMOSOME NUMBERSNUMBERS in mosaicsin mosaics

0

10

20

30

40

50

0В 1В 2В 3В 4В 5В 6В 7В

number of B-chromosomes

num

ber

of a

nim

als,

%

Magadan, Amur, Jewish & Khabarovsk Reg.Primorskiy Reg.

2525

NUMBER OF CELLULAR NUMBER OF CELLULAR CLONESCLONES

0

5

10

15

20

25

30

35

40

nu

mb

er o

f sp

ecim

ens,

%1 2 3 4 5

number of cellular clones

Magadan, Amur & Jewish Reg.

Khabarovsk Reg.

Primorsky Reg.

Mosaics were differed by number of cellular clones and their ratios. As a whole, number of clones was varied from 2 to 5 in mosaics from different localities. For example, from Amur and Jewish Regions near 40% animals had as prevailed three cellular clones and 30% had one clone (or stable karyotype). And from Khabarovsk and Primorsky Regions near 30% were specimens with two clones and near 40% ones had stable karyotypes.