Age structure and body size of the Strauch’s racerunner, Eremias strauchi strauchi Kessler, 1878

Abstract

We studied, for the first time, the age structure of Eremias strauchi strauchi (Kessler, 1878) from a sample (18 adults) of a population living in the vicinity of Iğdır (eastern Turkey) using the skeletochronological method. The maximum observed longevity was 7 years for males and 5 years for females. The age of males ranged from 4 to 7 years (mean 4.91, n = 12), while that of females ranged from 4 to 5 years (mean 4.66, n = 6). The average snout–vent length (SVL) was 61.10 mm in males and 60.82 mm in females. The differences in mean age and SVL between sexes were not statistically significant. Intersexual differences inbody size were male-biased, but this state was not statistically significant. Age and SVL were positively correlated in both sexes.

Full text

539
http://journals.tubitak.gov.tr/zoology/
Turkish Journal of Zoology
Turk J Zool
(2013) 37: 539-543
© TÜBİTAK
doi:10.3906/zoo-1212-18
Age structure and body size of the Strauch’s racerunner, Eremias strauchi strauchi
Kessler, 1878
Abdullah ALTUNIŞIK1,*, Çiğdem GÜL2, Nurhayat ÖZDEMİR1, Murat TOSUNOĞLU2, Tuğba ERGÜL1
1Department of Biology, Faculty of Arts and Sciences, Recep Tayyip Erdoğan University, Rize, Turkey
2Department of Biology, Faculty of Arts and Sciences, Çanakkale Onsekiz Mart University, Çanakkale, Turkey
* Correspondence: abdullah.altunisik@erdogan.edu.tr
1. Introduction
e Strauch’s racerunner (Eremias strauchi) is a small-size
lizard species belonging to the family Lacertidae, Reptilia.
Eremias strauchi has 2 subspecies. e nominative subspecies
(Eremias strauchi strauchi Kessler, 1878) ranges from South
Armenia and Azerbaijan (in Zuvand, Nakhichevan, and
southwestern Azerbaijan) into northwestern Iran and
Turkey (eastern Anatolia region in the vicinities of Iğdır
and Tuzluca). e second subspecies (Eremias strauchi
kopetdaghicaSzczerbak, 1972) is present in the Kopet Dagh
of northwestern Iran (northern Khorasan and eastern
Mazanderan) and southern Turkmenistan (Agasyan et
al., 2009). In Iran, the species has been recorded from
silty soil, red sandstone, slopes, ridges, and alluvial valleys
and the vegetation at the known sites is generally sparse,
overgrazed dry shrubs and steppe (Anderson, 1999). In
Turkey, the species is found in desert-like, dry open places
with pebbly substrates and little vegetation. ey feed on
insects and some plant material. e total body length is up
to approximately 200 mm. e dorsal surface of the body is
greenish brown-gray, spotless, and there are dark and light
maculations on the ventral region. e lizard hides in cracks
and crevices and can also burrow. e female lays 2 clutches
of 3–7 eggs annually (Baran and Atatür, 1998).
Many studies have been conducted about genus Eremias.
Some of these studies concern mating behavior (Kim et
al., 2012a), sexual size dimorphism (SSD) (Li et al., 2006),
reproduction (Tang et al., 2012; Yue et al., 2012), phylogeny
(Guo et al., 2011), home range (Kim et al., 2012b), and
genetics (Chen et al., 2012). e only demographic study
about this genus is on the species Eremias argus (Kim et
al., 2010). Although the morphological features of Eremias
strauchi strauchi (Ahmadzadeh et al., 2009) have been
studied, there are no data available about the age structure
of this subspecies.
Skeletochronology is a method for estimating age using
the presence of growth layers in bone tissue and counting
the lines of arrested growth (LAGs) (Castanet and Smirina,
1990). is method has been used to determine ages of
many amphibian and reptile species (Yılmaz et al., 2005;
Üzüm, 2009; Kim et al., 2010; Tomašević et al., 2010).
Although it has been stated that age determination by
skeletochronology in lizards deviates by 1 or 2 years from
ages calculated via the mark–recapture method (Smirina
and Tsellarius, 1996), skeletochronology has been preferred
to other methods because of its time-saving feature.
In this study, we describe for the rst time the age
structure, body size, and sexual dimorphism of an Eremias
strauchi strauchi sample population located in Iğdır, in
eastern Turkey.
2. Materials and methods
We used 18 preserved (12 ♂♂ and 6 ♀♀) Eremias strauchi
strauchi specimens stored in the herpetological collection
Abstract: We studied, for the rst time, the age structure of Eremias strauchi strauchi (Kessler, 1878) from a sample (18 adults) of a
population living in the vicinity of Iğdır (eastern Turkey) using the skeletochronological method. e maximum observed longevity
was 7 years for males and 5 years for females. e age of males ranged from 4 to 7 years (mean 4.91, n = 12), while that of females
ranged from 4 to 5 years (mean 4.66, n = 6). e average snout–vent length (SVL) was 61.10 mm in males and 60.82 mm in females. e
dierences in mean age and SVL between sexes were not statistically signicant. Intersexual dierences in body size were male-biased,
but this state was not statistically signicant. Age and SVL were positively correlated in both sexes.
Key words: Lacertidae, Eremias strauchi strauchi, age, sexual dimorphism, Turkey
Received: 14.12.2012 Accepted: 07.06.2013 Published Online: 12.08.2013 Printed: 06.09.2013
Research Article

ALTUNIŞIK et al. / Turk J Zool
540
of the Department of Biology Zoology Section at Çanakkale
Onsekiz Mart University, Turkey (Collection number:
84/2008). e specimens were randomly collected by hand
from Melekli village (39°58′N, 44°13′E, 838 m above sea
level), in the vicinity of Iğdır (in the east of Turkey, neighbor
to Armenia, Iran, and Nakhichevan) in 2008. Testudo graeca,
Phrynocephalus horv athi, Eremias pleskei, Trachylepis aurata ,
Malpolon monspessulanus, and Eryx jaculus are the other
reptile species located sympatrically with Eremias strauchi
specimens within the area. e specimens were obtained
from the surface of rocky and dune areas. e dominant
plant cover in the localities is composed of the species
Tribulus terrestris, Euphorbia sp., Eryngium sp., Artemisia
sp., Xeranthemum annuum, Petrosimonia squarrosa, Alhagi
sp., Astragallus sp., ymus pabescens, Aeluropus sp., Stipa
sp., Taeniatherum sp., Eremopyrum sp., Ziziphora sp., and
Achillea sp. (Tosunoğlu et al., 2011).
e specimens were captured between 0500 and 0900
in June and were xed in 95% ethyl alcohol and preserved
in glass jars with 70% ethyl alcohol. e annual mean
relative humidity in the region is around 63%. roughout
the year, the level of relative humidity reaches a maximum
value in December (73%) and a minimum value in July
(53%).
For each individual, we determined sex based on the
presence of a hemipenis, measured snout–vent length
(SVL) to the nearest 0.01 mm using digital calipers
(Mitutoyo Corp., Kawasaki, Japan), and clipped the
longest toe of the right hindlimb, including the rst and
second phalanges. Toe samples were stored in 70% ethanol
and successively used in histological analysis.
We estimated age using skeletochronology (Castanet
and Smirina, 1990). Aer the digits were dissected, the
phalanges were washed in running tap water for 24 h,
decalcied in 5% nitric acid for 2 h, and then washed
again under running tap water for 12 h and embedded
in cryomatrix (ermo). Cross-sections (16 µm) of the
diaphyseal part of each phalanx were obtained using a
freezing microtome and stained in Ehrlich’s hematoxylin.
e sections were submerged in glycerol for observation
under a light microscope. We assessed the endosteal
resorption of the rst LAG by comparing the diameters of
eroded marrow cavities with the diameters of noneroded
marrow cavities in sections from the youngest (4-year-
old) specimens. e number of LAGs was assessed
independently by 2 observers (A. Altunışık and T. Ergül)
and the results were compared.
Both SVL and age showed normal distribution
(Kolmogorov–Smirnov test, P > 0.05) and homogeneity of
variance (Levene test, P > 0.05). We used the independent
sample t test to compare variables between sexes and
Pearson’s correlation coecient was computed to infer the
pattern of relationships between SVL and age. e best
regression model was selected according to R2 values. Data
analysis was performed using SPSS 18.
We quantied SSD with the Lovich and Gibbons (1992)
index: sexual dimorphism index (SDI) = (size of larger sex
/ size of smaller sex) ± 1, where the result is arbitrarily
dened as positive (minus one) when females are larger
and negative (plus one) in the opposite case.
3. Results
Descriptive statistics of age and body length are
summarized in the Table. e average SVL of males was
61.10 ± 4.76 mm (range 52.01–71.38) and in females it was
60.82 ± 3.53 mm (range 55.13–63.65). LAGs were clearly
marked and relatively easy to count in all phalangeal cross-
sections as can be seen in Figure 1. e rst LAG was
partially eroded in 57% of the individuals and completely
eroded in 20% because of endosteal resorption, which
creates partial erosion of the periosteal bone on the edge of
the marrow cavity. In addition, we observed double lines
in 66% of the individuals.
e minimum age for adult lizards was found to be 4
years for both males and females. e maximum observed
lifespan was 7 years in males and 5 years in females. e
age of males ranged from 4 to 7 years (mean 4.91 ± 0.99, n
= 12), whereas those of females were 4 and 5 years (mean
4.66 ± 0.51, n = 6) (Figure 2). ere was no signicant
dierence in terms of mean age between the sexes (t =
–0.57, df = 16, P > 0.05).
SVL did not signicantly dier between females
and males (t = 0.13, df = 16, P > 0.05). Intersexual
dierences in body size were male-biased (SDI: –0.004),
but this state was not statistically signicant. A signicant
positive correlation was found between age and SVL in
males (r = 0.90, P < 0.01) and in females (r = 0.97, P <
0.01). Considering the small sample size of females, we
Tab l e . Age and SVL of an Eremias strauchi strauchi sample population.
Age (years) SVL (mm)
Sex N Mean ± SD Range Mean ± SD Range
Males 12 4.91 ± 0.99 4–7 61.10 ± 4.76 52.01–71.38
Females 6 4.66 ± 0.51 4–5 60.82 ± 3.53 55.13–63.65

ALTUNIŞIK et al. / Turk J Zool
541
performed regression analysis only for males and a simple
linear regression tted between age (x-axis = years) and
body size (y-axis = mm) (y = 39.97 + 4.29x, R2 = 0.809).
4. Discussion
We provide here the rst data on age and body size of
an Eremias strauchi strauchi sample population in Iğdır,
eastern Turkey. In our study, we found the maximum
observed longevity to be 7 years for males and 5 years for
females. For Eremias argus females and males, it has been
reported as 11 years and 8 years, respectively (Kim et al.,
2010).
In our study, the SVL mean of females did not
signicantly dier from that of males, although the
latter were bigger on average. Similar to our results, no
statistically signicant dierence between the sexes was
reported in the studies of Eremias multiocellata (Li et al.,
2006), Phymaturus patagonicus (Piantoni et al., 2006),
Lacerta agilis (Guarino et al., 2010), and Eremias argus
(Kim et al., 2010). In contrast to our study, the SVL mean
of females was signicantly larger than that of males in
Sceleporus undulatus (Haenel and John-Alder, 2002) and
Lacerta vivipara (Liu et al., 2008). Although Ahmadzadeh
et al. (2009), who studied the morphological features
of the same subspecies, Eremias strauchi strauchi, with
ecological and biological observations, found that the SVL
mean of females (64.96 mm) was larger than that of males
(64.01 mm), they did not support this nding with any
statistics. Our results resemble that study for not having
any statistically signicant dierences in terms of SVL.
Sexual dimorphism in body size, coloration, and a
variety of morphological characteristics is well known in
amphibians and reptiles. In lizards, aggressive interactions
among males appear to result in sexual dimorphism, and
males are larger than females regardless of whether or not
the lizards are territorial (Vitt and Caldwell, 2009). Males
are the larger sex in most lizards (Fitch, 1981). Some
authors have suggested that this sexual dimorphism has
evolved as a result of competition between the sexes for a
limited resource, usually food (Best and Gennaro, 1984).
Others have proposed that sexual selection, mediated by
male–male competition for mates, is the primary cause
(Vitt and Cooper, 1985; Hews, 1990). Because of sucient
food availability in Melekli village (pers. obs.), the latter
cause may be more important to explain our results.
In the present study, this lizard exhibited a very low
level of male-biased SSD in adult animals based on the
SVL. is result is in agreement with surveys of Agama
impalearis (El Mouden et al., 1999), Lacerta agilis
boemica (Roitberg and Smirina, 2006), and Dinarolacerta
mosorensis (Tomašević et al., 2010). However, no sexual
dimorphism was indicated between sexes based on the
SVL in the study of Eremias argus (Kim et al., 2010).
Lizards exhibit indeterminate growth, implying that
body size increases with age (Bauwens, 1999). In the
studied population, the relationship between age and SVL
is statistically signicant. Similar results have been recently
reported for some other lizard species (P. patagonicus,
Piantoni et al., 2006; D. mosorensis, Tomašević et al., 2010;
L. agilis, Guarino et al., 2010; E. argus, Kim et al., 2010).
In our skeletochronological samples, we observed a
consistent number of double LAGs appear as very closely
adjacent lines (Castanet et al., 1993). ese double LAGs
are caused by unpredictable ecological factors such as very
high temperatures, very dry conditions, variations in food
availability, and other occasional environmental changes
(Jakob et al., 2002; Guarino and Erismis, 2008). Iğdır has
asemiarid continental climate with hot dry summers, and
cold snowy winters, and is the driest city in Turkey (total
0
1
2
3
4
5
6
4 5 6 7
males
females
Number of individuals
Age (years)
Figure 1. A cross-section (16 µm in thickness) at the diaphysis
level of a phalanx of a female Eremias strauchi strauchi individual
(m.c. = marrow cavity, r.l. = resorption line, k.l. = Kastschenko
line, and e.b. = endosteal bone). e 5 LAGs are indicated by
black arrows (double LAGs with double arrows).
Figure 2. Age frequency distributions for males and females of
an Eremias strauchi strauchi sample population.

ALTUNIŞIK et al. / Turk J Zool
542
yearly precipitation of 260.3 mm) close to the borderline of
thearid climatethat nevertheless does not exist in Turkey
(www.dmi.gov.tr, Iğdır Observation Station, 1970–2011).
In Iğdır, a possible eect on growth of the arid period in
summer (mean temperature of 24.43 °C and maximum of
41.8 °C in August) and/or the cold period in winter (mean
of 1.43 °C and minimum of –30.3 °C in December) may be
the cause of the high percentage of double lines.
In conclusion, the results of our skeletochronological
analysis show that the specimens reached 7 years longevity
and intersexual dierences in body size were male-biased,
which was not statistically signicant. However, further
studies on a larger scale (i.e. more samples) or on the other
subspecies, Eremias strauchi kopetdaghica, would give us
more comprehensive data about the body size and age
structure of the species.
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