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This study examines the chromosome number variability and mosaicism of the Korean field mouse (Apodemus peninsulae) from the Russian Far East. The research analyzes the standard chromosome set and supernumerary chromosomes, as well as the size and morphology of B chromosomes. The occurrence and distribution of mosaics and stable karyotypes are also studied. The findings reveal a wide spectrum of B chromosome variability in mosaics compared to animals with stable karyotypes.
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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
Apodemus peninsulaeThomas, 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
The standard chromosome set and supernumerary chromosomes varying in number from 0 to 30- in Siberia and from 0 to 7 in the Russian Far East. of the Korean field mouse, Apodemus peninsulaecontains 48 acrocentric chromosomes 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)
The levels of B chromosome’s system variability in A. peninsulae: • intrapopulational, • Interpopulational, • tissue, or individual (mosaicism), • and variability of B’s differential staining.
THE AIM OF THE WORK WAS: • To study mosaicism on B chromosome of the Korean field mouse Apodemus peninsulae fromthe Russian Far East
MATERIAL OF THE STUDY OFApodemus peninsulae Thomas 1906 • The intra individual mosaicism of Bs was study in 355 animals collected at 41 continental natural localities of the Russian Far East. • There were specimens: from Magadan, Amur, Jewish and Khabarovsk Regions (n=87), • and also from Primorskiy Region (n=268).
DISTINGUISHING OF MOSAICS Mosaicism was evaluated on the basis of the number of cellular clones. Mosaics had two and more clones. Cellular clone - this is group of cells with the definite number of chromosomes. Cellular clones are isolated employing procedure D.K. Belyayev with co-authors (1974);and number of cells analysed was determined according E.B. Hook (1977). Clones are determined as the groups of the cells, when the hypoploid class composes 10% and more, and hyperploid - more or is equal to 5% (from the modal number of chromosomes).
Frequency of intra individual mosaicism of Bs • The wood mice have very frequentoccurrence of B chromosomes. It was found that 312 (87.9 %) animals possessed B chromosomes. • 219 (61.7 %) were mosaics with from two to five cellular clones and • only 136 (38,3%) mice had stable karyotypes.
MOSAICISM IN DIRRERENT POPULATIONS of A. peninsulae: a–Khabarovsk Reg., b – Primorskiy Reg. MagadanRegion Khabarovsk Regions AmurRegion JewishRegion Primorskiy Region
SPECTRA OF Bs NUMBER VARIATION Mosaics Stable MR – Magadan Region, AR – Amur Region, JR – Jewish Region, KHR – Khabarovsk Region, PR – Primorskiy Region; n - number of specimens.
METAPHASES WITH DIFFERENT В CHROMOSOMES 2n=48+4Bs m M m m ST M M M ST m 2n=48+2Bs 2M (middle and small) – Primorskiy Region (Ussuriyskiy Reserve) 2M+2ST (large and small) – Primorskiy Region (Nezhino vil.)
SIZE AND MORPHOLOGY TYPES OF B CHROMOSOMES (Bs) M Borisovskoye plateau Evoron Lake M M M M M M M SM ST M-mi M M-mi M 2n=48+7Bs 2n=48+7Bs Macro Bs: M –metacentrics, SM- submetacentic, ST-subtelocentric and mi - mini B chromosomes, seems as metacentrics (M).
THE B CHROMOSOME SYSTEM • There 78 variants of the B chromosome system have been first found out, distinguished by the number, size and morphology of B-chromosomes. • We described 22 variants in animals with stable karyotype (n = 136). The greatest variety of the variants (up 76) has been found in mosaics divided into two subgroups - with one and with two or more prevailing variants. In the first subgroup (n = 90) 68 and in another subgroup (n = 129) - 104 combinations of the variants have been revealed. • The combinations of the variants and their percent correlations were often unique.
DISTRIBUTION OF DEFINITE VARIANTS OF THE B CHROMOSOME SYSTEM b a As rule, sector “Other” includes unique variants of the B chromosome system
THE OCCURRENCE VARIANTS OF THE B CHROMOSOME SYSTEM Stable Mosaics b a • The optimum chromosome number (50) has been established as in animals with stable karyotype (a) and in mosaics (b) • Variants = size and morphology variants.
CONCLUSIONS: • The predominance of mosaics have been revealed in populations of the Russian Far East. • The percentage of mosaics are various both in the different populations and between the samples from one population, but practically no differences in the united populations of three geographic regions.
CONCLUSIONS: • The spectra of B chromosome variability were wider in mosaics (from 0 to 7) in comparison with animals with stable karyotype (from 0 to 4). • The optimum chromosome number (50) has been established in mosaics as well in animals with stable karyotype.
CONCLUSIONS: • The adaptive role of the low number of B chromosomes (1-2) is assumed and the B chromosome system seems not to be balanced in the species in whole. • The distribution of mice with the similar variants of the B chromosome system in the Far-Eastern populations of species seems to be of the chaotic nature.
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NUMBER OF CELLULAR CLONES 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.
