© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
Chromosomes
of some Species of Meriones (Mammalia: Rodentia)
By Charles
F.
1
Nadler and Douglas M. Lay
Eingang des Ms.
17.
1.
1967
The fourteen
species of jirds currently recognized to comprise the rodent genus Meriones
(Gerbillinae) occupy the Great Palearctic Desert from Mongolia to North
Africa.
Numerous investigators have dealt with the taxonomic relationships among the
and widespread genus. Heptner (1940) reported on the
Meriones inhabiting Iran. Ellerman (1941) recognized three subgenera: Para-
species of this interesting
species of
meriones, containing three species, Meriones, with 14 species, and Cheliones, with
one
The Classification proposed by Chaworth-Musters and Ellerman (1947)
though somewhat modified by more recent work provides the basis for current Classification of the genus. These authors recognized five subgenera and 13 species as
follows:
species.
Subgenus Sekeetamys
Meriones calurus
Subgenus Parameriones
M. persicus
M. rex
Subgenus
Cheliones
M. hurrianae
Subgenus
Subgenus
M.
M.
M.
M.
M.
M.
Pallasiomys
unguiculatus
meridianus
shawi
lihycus
arimalius
crassus
Meriones
M. tamariscinus
M. hlackleri
Meriones vinogradovi, though recognized
specifically,
was not placed
in
any sub-
Ellerman and Morrison-Scott (1951) using the System proposed by Chaworth-Musters and Ellerman (op. cit.) placed M. vinogradovi in the subgenus
Meriones. Zahavi and Wahrman (1957) in a study of the gerbils and jirds of Israel
showed that Meriones sacramenti constitutes a species distinct from M. crassus with
v/hich Chaworth-Musters and Ellerman (op. cit.) had synonymized it. Matthey
(1957) and Baltazard et. al. (1960) have presented evidence that M. hlackleri should
be recognized as a junior synonym of M. tristrami and that tristrami must be given
specific rank and not that of a subspecies of shawi as proposed by Chaworth-Musters
and Ellerman (op. cit.). Setzer (1961:88) in his review of the jirds of Egypt suggests
genus.
that
"doubtful that shawii exists as a species." All the Meriones species occurring
fauna of the USSR have been treated by Bobrinsky et al. (1944, 2nd ed. 1965)
and by Gromov et al. (1963). These works are identical in recognizing eight species.
Both use the name hlackleri for the species tristrami and the latter work in contrast
it is
in the
to the former
employs erythrourus for the species lihycus. Both recognize M. zarudnyi
whereas Chaworth-Musters and Ellerman (op. cit.) synonyform with M. crassus. Gromov et al. (op. cit.) employ two subgenera for
treated, but provide no rationale for this use. Their categories are:
as a distinct species
mized
this
the species
1
Financial support for this work was received from the National Science Foundation (Grants
3251, GB 5676X), U. S. Public Health Service (Gram AI 07384—01) and the Wallace C.
and Clara A. Abbott Memorial Fund of the University of Chicago.
GB
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
C. F. Nadler and D. M.
286
M. hlackleri
M. unguiculatus
Meriones
Subgenus
Lay
M.
M. vinogradovi
M. tamariscinus
M. zarudnyi
persicus
Subgenus
Pallasiomys
M. erythrourus
M. meridianus
as a genus. In summarizing the above
findings since 1947 into
incorporates
taxonomic views the following Classification
genus.
the
of
revision
cit.)
(op.
Ellerman's
Chaworth-Musters and
Petter (1956) has distinguished Sekeetamys
Subgenus
Genus Meriones
Subgenus
M.
persicus
M
rex
m
M.
M.
M.
M.
M.
M.
M.
Parameriones
Cheliones
Subgenus
M. hurrianae
Subgenus
Meriones
M. tamariscinus
M. tristrami
M. zarudnyi
M. vinogradovi
Pallasiomys
unguiculatus
meridianus
shawi
libycus
arimalius
crassus
sacramenti
Chromosomes have been analyzed from the following species: Meriones persicus,
M. vinogradovi, M. tristrami, M. shawi, M. libycus, M. crassus (Matthey 1953, 1954,
unguiculatus (Awa et al.
1957), M. sacramenti (Zahavi and Wahrman 1957), M.
ranged from 42 to 72
numbers
chromosome
diploid
reports
1959). According to these
number
and all species possessed 74 chromosome arms, designated the fundamental
Robertsonian
of
series
a
that
(FN), except tristrami which showed 76. This suggested
may have been responsible for evolution of the seemingly diverse
crassus (2n =
karyotypes (Matthey 1957). Because M. sacramenti (2n = 46) and M.
and
Ellerman
of
conclusion
the
60) possess distinctive chromosome complements,
rejecbeen
has
crassus
M.
represent
forms
these
of
both
that
Morrison-Scott (1951)
centric fusions
ted (Zahavi and
Wahrman
1957;
Matthey
Ellerman and Morrisonsubspecies of M. shawi (2n = 44),
1957). While
=
72) a
Scott (1951) make M. tristrami (2n
Matthey's (1953, 1957) chromosome studies present cogent evidence for specific recohave all yielgnition of M. tristrami. The studies of several independent investigators
of M. crassus
case
the
in
ded similar chromosomal data among the species studied except
Wahrman
(1957) desand
Zahavi
and
74
of
FN
where Matthey (1957) reported a
arms.
chromosome
of
number
unspecified
but
lesser
cribed a
Our purpose
is
to describe for the first time the
chromosomes of the
species
Meriones
were also
hurrianae representing the monotypic subgenus Cheliones. Chromosomes
in order to clarify the
Iran
and
Egypt
from
obtained
crassus
Meriones
from
analyzed
shawi,
problem concerning the karyotype and FN of this species. Specimens of M.
karyotypic
detailed
more
obtain
to
studied
were
M. unguiculatus and M. vinogradovi
methodology
data than available in the literature by employing newer cytogenetic
than was available to earlier investigators.
Materials and
The following specimens were
Pakistan:
Egypt:
studied: (1) Meriones hurrianae Jerdon, 1867,
West
Karachi), 2 males and 1 female; (2) Meriones shawi DuMatruh Governate; Bahig, Burg el Arab, one female born
Gizri (2 mi.
vernoy, 1842,
Methods
E
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
Chromosomes
of
some Speeles of Meriones
287
March 11, 1966, in Chicago of parents caught wild at the above locality (age 8months);
(3) M. unguiculatus Milne-Edwards, 1867, Laboratory stock of unknown history, one
male and one female; (4) M. vinogradovi Heptner, 1931, Iran unspeeified locality,
one female; (5) M. crassus Sundevall, 1842, Iran Isfahan Province; Mahallat, one
male born April 22, 1966, in Chicago of parental stock obtained wild from the above
locality (age 3 months); Egypt: exaet locality unkown, 2 males.
Specimens used in this study were identified using cranial and pelage characters
(Ellerman 1948, Petter 1961) and by comparison with specimens in the collections
:
:
Museum
of the Field
of Natural History, Chicago. These specimens are preserved in
Department of Anatomy of the University
the collection of the junior author at the
of Chicago. This study analyzes chromosomes obtained from femoral bone marrow
cells. Animals were injected intraperitoneally with one cc of a 0.05% coleemide
Solution and sacrificed after a lapse of two hours. Marrow clumps washed from the
femur with 1 °/o sodium citrate and subsequently aspirated gently through a 21 gauge
needle provided a Suspension of cells. After exposure in this hypotonic Solution at
room temperature for 15 minutes followed by centrifugation the supernatent was
removed and the cells fixed in acetic-alcohol (1:3) for 30 minutes. The fixative was
changed twice by centrifugation, 15 minutes per change and each time the cells were
resuspended in 1 cc of fresh fixative. A drop of the final Suspension was dried on a
microscope slide by gentle blowing and the chromosomes were stained 12 hours later
with acetic oreein. Chromosome counts were obtained from well spread metaphase
cells. Karyotypes were construeted from photomicrographs and the chromosomes
were arranged in seemingly homologous pairs aecording to size and centromere position
(acrocentric, submetacentric or metacentric).
Definite assignment of certain
chromosome pairs to either metacentric or submetacentric groups is difficult without
obtaining arm length ratios from a large number of specimens. Therefore, in this paper
Classification of some of these pairs is arbitrary. For the purpose of comparing different
taxa (Table 1) we have included metacentric and submetacentric autosomes in the same
Table
Chromosome
1
characteristics of
some
species of Meriones
Sex
Autosomes
Species
Subgenus
2 n
FN
M&S
Chromosom.
A
X
|
Reference
Y
|
M.
M.
M.
M.
M.
M.
M.
hurrianae
Cheliones
persicus
Parameriones
Pallasiomys
Pallasiomys
Pallasiomys
Pallasiomys
Pallasiomys
40
42
44
44
44
44
44
Pallasiomys
Pallasiomys
Pallasiomys
Meriones
Meriones
Meriones
46
60
60
72
44
44
unguiculatus
unguiculatus
shawi
shawi
libyeus
76
74
36
32
2
10
78
32
30
34
30
10
14
10
14
74
78
74
S
S
Present paper
Matthey, 1957
*
A Ava
S
S
S
*
*
*
et
al.,
1959
Present paper
Matthey, 1953, 1957
Present paper
Matthey, 1953, 1957
Zahavi
M. sacramenti
M. crassus
M. crassus
M. tristrami
M. vinogradovi
M. vinogradovi
FN —
total
centric, S
::
"
=
and Wahrman, 1957
74
72
74
74
78
14
10
2
30
34
46
48
70
14
10
S
S
A —
Present paper
*
Matthey, 1957
Matthey, 1954
*
Present paper
*
number of chromosome arms including
submetacentric,
Matthey, 1957
*
the sex chromosomes,
acrocentric chromosomes.
Sex chromosomes unidentified and inclu ded with autosomes.
M =
meta-
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
C. F. Nadler
288
and D. M. Lay
formorphologic category and have not utilized differences in these chromosomes in
in these species
distinguished
readily
are
however,
Acrocentrics,
conclusions.
mulating
much greater confidence.
of Menones and can be utilized as taxonomic characters with
the number of autocounting
by
computed
usually
The fundamental number (FN) is
possesses two arms
submetacentric
and
metacentric
Each
karyotype.
the
in
arms
some
in a
and each acrocentric possesses one. However, in this report the FN is computed
material;
published
previously
with
comparison
difTerent manner in order to facilitate
are totaled to arrive at the FN.
all chromosome arms including the sex chromosomes
Results
(2n) of Menones hurnanae is 40. The karyotype
and 2 acrocentric autosomes. Cells from
submetacentric,
10
contains 26 metacentric,
chromosome,
and
a smaller submetacentric
submetacentric
large
a
show
males
the
chromosomes (Fig. 1).
whereas cells from the female possess two submetacentric
The diploid chromosome number
Y
X
X
The FN is 76.
M. unguiculatus pos-
U Ii XX KX xx xx
•
m r*
mm nn
pH1 it
H f* in
Jd pt
Hg
m
ii^ mm
«
a 2n of 44 and a
karyotype constaining 22
metacentric, 10 submetacentric and 10 acrocenseses
autosomes,
tric
smaller submetacentric
Y
FN
is
78 (Fig.
*\n
Ii am II
XX
44.
2).
M. shawi has a 2n of
The karyotype dis-
plays 22 metacentric, 12
submetacentric and 10
autosomes.
acrocentric
1.
Chromosomes
of
Menones hurnanae
large
and a
chromosome. The
mV
Fig.
a
X
submetacentric
Two
large
metacentric
chromosomes observed
II
U n n ii u
in
the single female examined may likely represent
the
X
chromosomes beX chromosomes
species of Meriones
cause the
of
all
reported in the literature
IS
it vi it »a
are of this morphological
type.
however,
(Note,
inclusion
of
large
this
pair with the metacentric
group
i» )i
i% i»
A0 tft *A «* •*
Iii
Fig. 2.
Chromosomes of Menones unguiculatus
is
above).
The
FN
78 (Fig. 3).
M. vinogradovi has a
2n of 44 and karyotype
that cannot be differentiated from M. shawi.
only
Because
were analyzed
females
the
sex
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
Chromosomes of some
chromosomes cannot be
with certainty.
identified
FN is 78 (Fig. 4).
Specimens of M. cras-
The
XI
from Egypt and Iran
have a 2n of 60 and the
Speeles of Meriones
289
U lK YXIIXX
sus
yM W V %
P * Ä A XX X X
i • ^ g
karyotypes of the representatives of two widely
separated populations are
S\
The
indistinguishable.
male
karyotype
two
metacentric,
fl
shows
eight
™
§k
submetacentric including
a
minute pair,
acrocentric
The
X
A*
Äft
*A 4*
A
^ ^ #§
J>\
|^
Jfe
Ü
4
and 48
^g-
autosomes.
chromosome
is
3.
Chromosomes of Meriones shawl
a
submetacentric larger than any of the autosomes.
in size to the third largest pair of submetacentric
minal centromere. The
FN is
72 (Fig.
- The Y is a submetacentric equal
autosomes but possesses a more ter-
5).
W KI X* 2
HK
XX
ftff #4.1
i*Vg. 4.
*|
**
m «a «*
Chromosomes of Meriones vinogradovi
Discussion
Companson of the chromosomal characters of nine species of Meriones in
Table 1
shows a number of differences between our data and that
reported earlier by other
investigators. Matthey (1953, 1954,
1957) reports data derived from testicular
preparations prior to the advent of the newer cytological
methods that employ
hypotonic Solutions and colchicine to enhance chromosome spreading
and hence study
chromosome morphology. Because of the less accurate older methodology
for determination of chromosome morphology it seems likely that the
discrepancies are due to
these differences in technique. Zahavi and
Wahrman (1957) did not describe their
method of chromosomal analysis but because they do not report
karyotypic information other than the Statement that M. crassus possesses a
lower FN than other
of
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
C. F. Nadler and D. M.
290
Lay
1K
OA
KU §*
fl ft
/»*
(1
r\
•>
fl f 1
WH
*
II
fs
n
»
1
"
o
iv
II f$
i\
n*
Y
X
*
Fig. 5.
fl
Chromosomes ofMeriones
««
crassus
Awa
et
aL (1959)
seems inconsequential. F.nally
species of Meriones this neglect
44 chromosomes for
culture and hypotonic saline report
ehromosomes in eaeh morpholog.c
of
number
the
bn faU to specifically enumerate
number reported for any
That no disagreement exists in the diploid
M
Stile
tvoe and
l FN
of
and only slighAisagreement in features
certamly
stud.es
previous
of
between our results and those
of^e spiL
tuositv of these earlier investigators.
The earlier observations of a similar
^—^^
refleets credit to the vtr
.
(,/•.„..
Menones
(74-76) in the studied species of
high to low dipknd
from
evolution
karyotype
of
suggested a continuous sequence
Our Observation
Robertsoman centric fusions (Matthey 1957
number
" bv
"f
FN
.
a series of
veral different
FNs
within the genus suggests karyotype
important
as pencentnc inversions. It seems
gements in addition to centric fusion, such
of
taxonomy
the
concermng
l correlate chromosomal data with present views
J
M
of species of the.genus Meriones
TheTequence of the diploid chromosome numbers
and the
the monotypic subgenus Cbehones
spans 40 to 72 (cf. Table 1). Excluding
one of
only
for
made
been
has
analysis
subg nus Paramenones for which karyotype
Mernes
subgenera
recognized
two
other
the
hetwo constituent species, neither of
»>
group on the basis of
or Pallasiomys, represents a distinctive
and 44, 46 and 60 in
differ, 44 and 72 in the former
subgenera
these
of
species
The
of
studied karyotypically todate Evidence
the latter for those component species
thus
Meriones and Pf^umys
chromosome numbers for species of the subgenera
,
diploid chromo-
may not represent natural groupings. The data of
to the
at least six groups correspondmg
some numbers known for Meriones imply that
genus
Ae
in
recognized
(cf. Table 1) may be
diploid numbers 40, 42, 44, 46, 60 and 72
acrocentncs and few metacentncs haye
Karyotypes with higher diploid number, many
suggests that these
with a lower diploid number few acrobeen considered more primitive than those
tnst arm
In th.s respect M.
and many metacentrics (Bender and Chu 1963).
may be regarded as
respectively
60
and
and M. erassus with diploid numbers of 72
species studied to date,
rema.mng
seven
the
of
any
than
chromosomally more primitive
Table 1).
which ränge in diploid number from 40-46 (cf.
may evolve from low to high
The problem of whether mammalian karyotypes
centrics
'
© Biodiversity Heritage Library, http://www.biodiversitylibrary.org/
Chromosomes
of some Species of Meriones
291
diploid numbers by Association of metacentric
chromosomes remains unresolved.
When otner lines of evolutionary evidence are analyzed, Meriones
may off er a promising model for assailing this important question.
Summary
All previous chromosomal data concerning the
genus Meriones is reviewed. The previously
ld an d iUnd
Pe d
numbers of Arianes hurnanae ar/pre'ent cd
for the first time. The
h fundamental
f
u* of
T?}
number
M. ungmculatus is published for the initial time
Evidence 1S presented to show that the fundamental
number of M. shawt and M. vinogradTvi
is 78 and not 74 as previously indicated
by Matthey (1953, 1954, 1957). The fundamental
number of
crassus is shown to be 72 and not 74 as
stated by Matthey (1957). Karyotypes
are presented for
ungmculatus,
shawi, M. crassus and M. vmogradovi. It is
suggZted
on the evidence of chromosome numbers that the
subgenera Meriones and Pallasiomy] sensu
Chaworth-Musters and Ellerman (1957) represent unnatural
groupings and tha7at Teast
least
six groups may be recognized in the genus.
™?tetltt77
m
f°
,
,
.
M
M
M
6*5
Acknowledgements
W
a ,itude
Z
1
fi A
Ztd t\hlZ^TE Rabb
nk Df J ° SEI>H C
'
suggTstions
the follow j?S lg«*»
J°
Hoogstraal, Dr. Mahmoud
M ° ORE
-
f° r
provided us with the animals
Bahmanyar, and Dr. George
readlng the manuscriP* a "d Offling hi s helpful
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Author's address: Charles F Nadler and
Douglas M. Lay, Division of Mammals, Field
Museum of Natural History, Chicago, USA