Nazan Üzüm

Age, size and growth of the southern crested newt Triturus karelinii (Strauch 1870) in a population from Bozdag (Western Turkey)

We studied the characteristics of bone growth assessed by skeletochronology in a southern crested newt Triturus karelinii (Urodela) population from Western Turkey. The timing and patterns of bone arrested growth were observed using the phalanges of juveniles and adults that were caught in spring at a breeding site. A metamorphosis line was found in the juveniles. In some adults, a classical succession of single lines of arrested growth was observed in about 50% of the cross sections. However, the other adults exhibited a succession of double lines of arrested growth in their phalanges. Due to the arid summer and cold winter climate in the Bozdag region (1200 m a.s.l.), we argue that in this last case, the lines of arrested growth were deposited during both the summer (aestivation) and winter (wintering). Body length, age and growth were similar in males and females. The age of maturity was 3 to 4 years old and longevity was 8 and 11 years in males and females respectively. Body length and age among taxonomically related large bodied newts of the T. cristatus complex were reported from populations experiencing various environmental conditions. Body length and age at maturity were similar to that observed in other newt species. However, longevity seems to be lower than expected in the T. karelinii studied population. We hypothesized that the arid climate of Bozdag could cause a higher mortality risk during the terrestrial phase of the life cycle. Studying more populations exposed to various conditions is clearly needed to assess interpopulational variation of these life-history traits in this newt species.

Gregarious behaviour in a salamander: attraction to conspecific chemical cues in burrow choice

Gregarious behaviour (i.e. living in groups in contrast to a solitary life) is commonly observed in mammals, but rarely documented in amphibians. Environmental features and/or animal mutual attractions can promote the formation of aggregations that may both reduce the risks of dehydration and predation and increase mate access and fitness. Luschan’s salamander (Mertensiella luschani) lives in permanently arid Mediterranean environments; individuals shelter in cracks and crevices and leave only during favourable periods. In this study we examined the role of chemical tracks, in self and conspecific recognition (i.e. gregarious/solitary behaviour), on the social structure of this species. Our results show that juveniles and adults of both sexes use chemical scents deposited on substrate to relocate their shelter. In contrast to numerous other salamander species, Luschan’s salamanders also use social information, conveyed by conspecific scents, to identify a safe shelter. Furthermore, this scent marking does not play a role in sexual attraction but allows sex discrimination. This species exhibits gregarious behaviour (i.e. conspecific attraction) as a possible adaptation to dry environments. We discuss both ultimate and proximate factors in the evolution from a solitary to a gregarious life.

AGE, SIZE AND GROWTH IN TWO POPULATIONS OF THE SOUTHERN CRESTED NEWT, TRITURUS KARELINII (STRAUCH 1870) FROM DIFFERENT ALTITUDES

Abstract We measured body size of individuals from two populations of the southern crested newt, Triturus karelinii, from two localities at different altitudes (7 m, Klaros and 1373 m, Reşadiye) in Turkey. Lines of arrested growth (LAGs) recorded in phalanges were used to estimate the age of juveniles and adults. Females were on average larger than males in Klaros, and males were on average larger than females in Reşadiye. Our results did not follow the Bergmanns rule and developmental temperature-size rule: for both sexes, the individuals of lowland population were larger than the individuals of highland population. Significant differences were found between the populations in terms of mean SVL (snout–vent length). The average age was calculated as 6.14 ± 1.51 and 6.16 ± 1.46 yr in Klaros and 5.30 ± 1.20 and 5.76 ± 1.26 yr in Reşadiye, for males and females respectively. No significant differences were found between the age distributions of the females in both populations. Both sexes from lowland population had age distributions that were similar to their counterparts from highland population. The growth curves for T. karelinii populations were well described in a Von Bertalanffy growth model. K was not significantly different between the sexes. However, SVLmax was significantly larger in females than males in both populations

A genomic footprint of hybrid zone movement in crested newts

Speciation typically involves a stage in which species can still exchange genetic material. Interspecific gene flow is facilitated by the hybrid zones that such species establish upon secondary contact. If one member of a hybridizing species pair displaces the other, their hybrid zone would move across the landscape. Although theory predicts that moving hybrid zones quickly stagnate, hybrid zones tracked over one or a few decades do not always follow such a limitation. This suggests that hybrid zones have the potential to traverse considerable distances over extended periods of time. When hybrid zones move, introgression is predicted to result in biased gene flow of selectively neutral alleles, from the receding species into the advancing species. We test for such a genomic footprint of hybrid zone movement in a pair of crested newt species (genus Triturus) for which we have a priori support for westward hybrid zone movement. We perform a multilocus phylogeographical survey and conduct Bayesian clustering analysis, estimation of ancestry and heterozygosity, and geographical cline analysis. In a 600 km wide area east of the present day hybrid zone a genomic footprint constitutes empirical evidence consistent with westward hybrid zone movement. The crested newt case suggests that hybrid zone movement can occur over an extensive span of time and space. Inferring hybrid zone movement provides fundamental insight into historical biogeography and the speciation process, and we anticipate that hybrid zones will prove to be far more mobile than currently appreciated.

Body size and age structure of Pelophylax ridibundus populations from two different altitudes in Turkey

We estimated differences in body size and age structure of two populations of Pelophylax ridibundus living at different altitudes in Turkey, one from Dortyol (6 m a.s.l.) and the other from Karagol (1480 m a.s.l.). Their age structure was determined by skeletochronology performed on the LAGs (lines of arrested growth) of the phalanges. While ages ranged from 2 to 8 years for males and from 2 to 7 years for females in Karagol, in Dortyol the ages ranged from 4 to 11 years for males, and 3 to 7 years for females. Sexual size dimorphism was only found in the Dortyol population. Larger females tend to be found in hotter climates (Dortyol) but reach maturity later (3-4 years) than the highland population (2 years). A significant relationship between age and snout-vent length (SVL) was found for both sexes and populations with the exception of females in Dortyol.

Body size and age structure of a breeding population portion of the Urmia salamander, Neurergus crocatus Cope, 1862 (Caudata: Salamandridae)

Abstract Recently, the Urmia salamander, Neurergus crocatus Cope, 1862 was classified as a vulnerable species. The age structure of a breeding population portion of N. crocatus from Turkey was studied by using skeletochronology performed on the phalanges. According to the analysis of the age structure based on counting lines of arrested growth (LAGs), ages ranged from 5 to 14 years (mean = 9.4 ± 2.3 years) for males and from 8 to 17 years (mean = 11.6 ± 2.2 years) for females in N. crocatus. The mean snout–vent length was 69.2 ± 3.6 mm in males and 76.2 ± 3.8 in females. The sexual dimorphism index was 0.10. The difference between the sexes in age and size was statistically significant.

Phylogeny of Neurergus crocatus and Neurergus strauchii in Turkey Based on Morphological and Molecular Data

Abstract We described the phylogeny of the salamandrid genus Neurergus in Turkey using statistical analyses on morphometric characters and a molecular analysis based on 12S and 16S rRNA genes. Two different species, Neurergus crocatus and Neurergus strauchii (N. s. strauchii and N. s. barani), are reported from new localities. Morphologically, the only significant differences between N. s. strauchii and N. s. barani were eye width, head width, and forelimb length in females; and eye width, head length, head width and inter-nostril distance in males in terms of 12 external morphometric measurements, with N. s. barani having larger values. According to PCA, species segregated along morphological axes and all the variables (except inter-limb and eye width in males and except longest toe forelimb, head width, eye width and inter-orbital distance in females) were important in separating species along these axes. We obtained a total of 833 basepairs (bp) of two mitochondrial genes (478 bp of 12S rRNA and 355 bp of 16S rRNA) from Neurergus crocatus (n  =  10), Neurergus strauchii strauchii (n  =  9) and N. s. barani (n  =  9). Neurergus crocatus differed from N. s. strauchii and N. s. barani with sequence divergences of 4.5%–5.1% and 5.4%–5.5%, respectively. However, among three haplotypes of N. s. strauchii, sequence divergence was very low (0.24% to 0.96%). The nucleotide difference between these two subspecies ranged from 0.48% to 1.2%. As a result, N. s. barani specimens in this study were not strongly differentiated from N. s. strauchii, suggesting that their distributions are either connected or only recently separated or that N. s. barani does not represent a distinct genetic unit.

Effects of Ca2+ channel blocker verapamil on tissue regeneration in a lizard tail autotomy model: a biochemical and histological study

Ca2+ ions have been reported to augment the activities of many cell types including cellular proliferation and tissue regeneration. Moreover, it is well known that verapamil is a L-type voltage-gated Ca2+ antagonist with important clinical implications. To evaluate the role of Ca2+ ions in the regeneration of tail in lizards, verapamil was used in vivo to modulate the activity of intracellular Ca2+ in a lizard tail autotomy model. A total of 35 adult lizards were divided into three groups: lightness control group ( n = 11), darkness group ( n = 11) and verapamil treatment group ( n = 13). The tails of adult lizards were amputated by pinching off the tail at the 15 th segment from the vent to induce tail regeneration. The first two groups served as untreated constant lightness and darkness groups as controls, but the remaining group received intraperitoneally 1 mg/kg of verapamil. Following autotomy, the length of regenerating tails was measured at 10, 15, 20, 25, and 30 days post-amputation. At the end of the study, the regenerating tails from animals from each group were removed for collagen assay procedure and histological examination. We found that verapamil produced a reduction in the length of the regenerated tail compared to untreated lightness group and the percentage of tail replaced in verapamil treatment group was lower than those in lightness control group. Total collagen contents were found to be higher in lightness control group in comparison with darkness and verapamil treatment groups. Accordingly, a quantitative stereological evaluation showed a higher percentage of neural tissue and a lower percentage of connective tissue, as well as vascular tissue, in the cross-sections of the regenerated tails taken from Ca2+ channel blocker verapamil-treated lizards, as compared to other groups. In conclusion, our results suggest that verapamil influences a variety of processes including fibroblast collagen production, neurogenesis, and angiogenesis during tail regeneration in lizard, possibly due to inhibition of intracellular Ca2+ ion by verapamil.

Absence of heterosis in hybrid crested newts

Relationships between phylogenetic relatedness, hybrid zone spatial structure, the amount of interspecific gene flow and population demography were investigated, with the newt genus Triturus as a model system. In earlier work, a bimodal hybrid zone of two distantly related species combined low interspecific gene flow with hybrid sterility and heterosis was documented. Apart from that, a suite of unimodal hybrid zones in closely related Triturus showed more or less extensive introgressive hybridization with no evidence for heterosis. We here report on population demography and interspecific gene flow in two Triturus species (T. macedonicus and T. ivanbureschi in Serbia). These are two that are moderately related, engage in a heterogeneous uni-/bimodal hybrid zone and hence represent an intermediate situation. This study used 13 diagnostic nuclear genetic markers in a population at the species contact zone. This showed that all individuals were hybrids, with no parentals detected. Age, size and longevity and the estimated growth curves are not exceeding that of the parental species, so that we conclude the absence of heterosis in T. macedonicus–T. ivanbureschi. Observations across the genus support the hypothesis that fertile hybrids allocate resources to reproduction and infertile hybrids allocate resources to growth. Several Triturus species hybrid zones not yet studied allow the testing of this hypothesis.