Common Snake Research Articles

Cellular Turnover: A Potential Metabolic Rate-Driven Mechanism to Mitigate Accumulation of DNA Damage.

Oxidative stress, the imbalance of reactive oxygen species and antioxidant capacity, may cause damage to biomolecules pivotal for cellular processes (e.g., DNA). This may impair physiological performance and, therefore, drive life-history variation and aging rate. Because aerobic metabolism is supposed to be the main source of such oxidative risk, the rate of oxygen consumption should be positively associated with the level of damage and/or antioxidants. Empirical support for such relationships remains unclear, and recent considerations suggest even a negative relationship between metabolic rate and oxidative stress. We investigated the relationship between standard metabolic rate (SMR), antioxidants, and damage in blood plasma and erythrocytes for 35 grass snakes (Natrix natrix). Reactive oxygen metabolites (dROMs) and nonenzymatic antioxidants were assessed in plasma, while two measures of DNA damage and the capacity to neutralize H2O2 were measured in erythrocytes. Plasma antioxidants showed no correlation to SMR, and the level of dROMs was positively related to SMR. A negative relationship between antioxidant capacity and SMR was found in erythrocytes, but no association of SMR with either measure of DNA damage was detected. No increase in DNA damage, despite lower antioxidant capacity at high SMR, indicates an upregulation in other defense mechanisms (e.g., damage repair and/or removal). Indeed, we observed a higher frequency of immature red blood cells in individuals with higher SMR, which indicates that highly metabolic individuals had increased erythrocyte turnover, a mechanism of damage removal. Such DNA protection through upregulated cellular turnover might explain the negligible senescence observed in some ectotherm taxa.

Letea Virus: Comparative Genomics and Phylogenetic Analysis of a Novel Reassortant Orbivirus Discovered in Grass Snakes (Natrix natrix).

The discovery and characterization of novel arthropod-borne viruses provide valuable information on their genetic diversity, ecology, evolution and potential to threaten animal or public health. Arbovirus surveillance is not conducted regularly in Romania, being particularly very scarce in the remote and diverse areas like the Danube Delta. Here we describe the detection and genetic characterization of a novel orbivirus (Reoviridae: Orbivirus) designated as Letea virus, which was found in grass snakes (Natrix natrix) during a metagenomic and metatranscriptomic survey conducted between 2014 and 2017. This virus is the first orbivirus discovered in reptiles. Phylogenetic analyses placed Letea virus as a highly divergent species in the Culicoides-/sand fly-borne orbivirus clade. Gene reassortment and intragenic recombination were detected in the majority of the nine Letea virus strains obtained, implying that these mechanisms play important roles in the evolution and diversification of the virus. However, the screening of arthropods, including Culicoides biting midges collected within the same surveillance program, tested negative for Letea virus infection and could not confirm the arthropod vector of the virus. The study provided complete genome sequences for nine Letea virus strains and new information about orbivirus diversity, host range, ecology and evolution. The phylogenetic associations warrant further screening of arthropods, as well as sustained surveillance efforts for elucidation of Letea virus natural cycle and possible implications for animal and human health.

Variation in the formation of crista sellaris and basisphenoid in the skull of the grass snake Natrix natrix embryos (Serpentes, Colubridae)

The crista sellaris is one of the basic structures of the snake chondrocranium. In embryogenesis it ossifies, forming the basisphenoid. This article describes variations of the crista sellaris, which, in turn, leads to variation in the formation of the basisphenoid in the skull of grass snake Natrix natrix (Serpentes, Colubridae) embryos. Several embryos at different developmental stages are investigated. Embryos from one developmental stage are taken simultaneously from one clutch. Thus, variation of the crista sellaris and basisphenoid in the skull of embryos is discovered, including those from one clutch. In several embryos, the crista sellaris is absent or partially formed. The absence of the crista sellaris does not preclude the formation of the basisphenoid. Based on the observed variations of the crista sellaris, the basisphenoid may have a different origin. In embryos with formed crista sellaris, the basisphenoid develops as a complex endochondral bone from three ossification centers (paired-in the polar cartilages and unpaired in the crista sellaris). In embryos without fully formed crista sellaris the basisphenoid develops as a paired bone of mixed origin: endochondral ossification appears in the polar cartilages, but where the crista sellaris is absent, it is formed by dermal ossification. In general, we observed the absence of the crista sellaris in 15% of studied embryos. We assume that it may be due to a reduction of the orbital-temporal region of the chondrocranium in N. natrix embryos. RESEARCH HIGHLIGHTS: The variation of the crista sellaris and basisphenoid formation in grass snake embryos is revealed. Depending on the presence or absence of the crista sellaris, basisphenoid is formed as a complex chondral bone or as a paired bone of mixed origin.

Individual features of geometric figures discrimination by three species of reptiles

Background (context). The individual characteristics of reptiles have been studied less than that of other classes of animals. One of the basic properties of their individuality, impulsivity, on which behavior and the solution of cognitive tasks in humans and animals significantly depend, has not been practically investigated. Objective. To study manifestations of impulsivity in decision-making in visual recognition in three types of reptiles. Design. In ten experiments, each of six individuals of three reptile species chose one of two paths in the task of distinguishing geometric shapes in mazes. The indicators of the percentage of erroneous choices and the average time for making choices were evaluated relative to the corresponding median values, similar to the study of a person’s impulsivity when choosing among similar visual images in the Kagan test. Results. Among the individuals of each species, four individual typological groups were distinguished: impulsive, slow — accurate, fast — accurate, and slow — inaccurate. This confirmed the authors’ hypothesis based on their study of color recognition in common grass snakes. In slow — accurate and slow — inaccurate individuals, repeated turns to the stimuli being compared were observed before they made a decision, apparently reflecting the expanded analysis of visual information, unlike in most impulsive and fast-accurate individuals. Conclusions. The four individual-typological groups identified in the three types of reptiles in the task of visual recognition are similar in terms of impulsivity to the known groups of people identified in a similar task. The differences in the behavioral reactions of individuals of the four typological groups of reptiles before making a decision correspond to the different psychological content of such a choice in these groups. Our results, which were obtained for reptiles for the first time, confirm the concept of impulsivity as one of the fundamental biologically determined characteristics of individuality, which is valid for other species of animals and humans. In the future it would be useful to find out: 1. Whether the following methods of studying impulsivity evaluate the same individual characteristic of animals: the well-known method of choosing the type of reinforcement and the auto method of choosing the path in the labyrinth with visual discrimination; 2. Do the assessments of impulsivity by these methods correlate with assessments of courage in reactions to a new object, territory and food? The practical significance of the work lies in the fact that knowledge of the individual characteristics of reptiles allows us to develop scientifically based recommendations for maintaining their well-being in zoos and nurseries.

New dietary records and geographic variation in the diet composition of the snake Philodryas nattereri in Brazil

Regional data on the natural history of snakes are important for understanding patterns of ecological geographic variation of widely distributed species. In this study, we report new dietary data about the South American dipsadine snake Philodryas nattereri in the Caatinga and Atlantic Forest regions of northeastern Brazil. Our observations in the wild include predation on large-sized lizards ( Iguana iguana ), adult birds ( Columbina picui ), venomous toads ( Rhinella jimi and R. granulosa ), snakes ( Lygophis dilepis ), bird chicks inside nests ( C. picui, Tangara sayaca and Troglodytes musculus ), nocturnal-crepuscular terrestrial mammals ( Galea spixii ) and strictly nocturnal flying mammals ( Artibeus planirostris ). Besides bringing new data about feeding habits of P. nattereri , we also compare its diet composition between the Caatinga and the Cerrado, the Brazilian ecoregions that are part of the South American dry diagonal, by pooling our original data with all available literature records. The diet composition of P. nattereri is significantly different between these two regions: lizards comprise the predominant prey category for P. nattereri in the Caatinga (57.6 %), whereas mammals stand out as the most reported prey category in the Cerrado (67.2 %). Our results evidence generalist and opportunistic feeding habits of P. nattereri , one of the most common snake species in non-strictly forest ecosystems of Brazil.

Toxoplasma gondii infection in selected species of free-living animals in Poland.

Free-living animals can play an important role as a reservoir of Toxoplasma gondi;, however, data concerning this issue in Poland are still limited.The aim of study was to assess the occurrence of T.gondii infection by using molecular methods in free-living animals in selected regions of Poland. Tissues samples of 396 animals (foxes, muskrats, birds, martens, badgers, polecats, raccoons, minks, raccoon dogs, otters, small rodents and insectivores, and grass snakes were collected from various regions of Poland. After samples digestion, DNA was isolated using QIAmp DNA Mini Kit (Qiagen). DNA extraction from small rodents and insectivores samples was performed without digestion. Next, nested PCR (B1 gene) and, for a part of nested PCR positive amplicons, RFLP PCR, were performed according to the method by Grigg and Boothroyd (2001). The other part of nested PCR positive DNA isolates were genotyped using 5 genetic markers: SAG1, SAG2 (5'- and 3'), SAG3, BTUB and GRA6, based on the method by Dubey et al. (2006). These PCR products were sequenced and compared with the NCBI database using Blast. In total, in 50 of the 396 examined animals DNA of T. gondii was detected (12.6%). The highest percentages of positive results in PCR was obtained in martens (40.9%) and badgers (38.5%), lower in birds (27.3%) and the lowest in foxes (7.4%). The RFLP and multilocus PCR analysis showed the dominance of T. gondii clonal type II (or II/III). The results of this study indicate the frequent T. gondii infection among free-living animals in Poland, especially martens and badgers, which may indirectly indicate that these animals contribute to the spread of the parasite in the sylvatic environment in Poland. The genotyping analysis showed the dominance of T. gondii clonal type II (or II/III).

Development of pancreatic acini in embryos of the grass snake Natrix natrix (Lepidosauria, Serpentes).

This study report about the differentiation of pancreatic acinar tissue in grass snake, Natrix natrix, embryos using light microscopy, transmission electron microscopy, and immuno-gold labeling. Differentiation of acinar cells in the embryonic pancreas of the grass snake is similar to that of other amniotes. Pancreatic acini occurred for the first time at Stage VIII, which is the midpoint of embryonic development. Two pattern of acinar cell differentiation were observed. The first involved formation of zymogen granules followed by cell migration from ducts. In the second, one zymogen granule was formed at the end of acinar cell differentiation. During embryonic development in the pancreatic acini of N. natrix, five types of zymogen granules were established, which correlated with the degree of their maturation and condensation. Within differentiating acini of the studied species, three types of cells were present: acinar, centroacinar, and endocrine cells. The origin of acinar cells as well as centroacinar cells in the pancreas of the studied species was the pancreatic ducts, which is similar as in other vertebrates. In the differentiating pancreatic acini of N. natrix, intermediate cells were not present. It may be related to the lack of transdifferentiation activity of acinar cells in the studied species. Amylase activity of exocrine pancreas was detected only at the end of embryonic development, which may be related to animal feeding after hatching from external sources that are rich in carbohydrates and presence of digestive enzymes in the egg yolk. Mitotic division of acinar cells was the main mechanism of expansion of acinar tissue during pancreas differentiation in the grass snake embryos.

A snake in the grass: Genetic structuring of the widespread African grass snake (PsammophylaxFitzinger 1843), with the description of a new genus and a new species

Psammophylax (Fitzinger 1843) is a widespread yet poorly studied genus of African grass snakes. A genetic phylogeny of six of the seven species was estimated using multiple phylogenetic and distance-based methods. To support the genetic analyses, we conducted morphological analyses on the body (traditional morphology) and head (geometric morphometrics) separately. Phylogenetic analyses recovered a similar topology to past studies, but with better resolution and node support. We found substantial genetic structuring within the genus, supported by significantly different head shapes between P. a. acutus and other Psammophylax. Psammophylax a. acutus was recovered as sister to its congeners, and sequence divergence values and morphometrics supported its recognition as a new genus. Increased sampling in East Africa (Tanzania, Kenya, and Ethiopia) revealed that Psammophylax multisquamis is polyphyletic, necessitating the description of a new, morphologically cryptic species from northern Tanzania. The distribution of P. multisquamis sensu stricto is likely restricted to Kenya and Ethiopia. The study has further resolved multiple aspects of Psammophylax systematics, including the taxonomic validity of two central African subspecies, P. variabilis vanoyei (Laurent 1956) and P. tritaeniatus subniger (Laurent 1956). Inclusion of specimens from the more remote parts of Africa, in future analyses, may result in the recovery of additional diversity within Psammophylax.

Population and ecological characteristics of the dice snake, Natrixtessellata(Laurenti, 1768), in lower portions of the Vrbanja River(Republic of Srpska, Bosnia and Herzegovina)

Despite their comparative richness and accessibility in the Republic of Srpska and in Bosnia and Herzegovina in general, population studies of reptiles have not been performed in Srpska until recently. For example, one of the most common snake species in this area is the dice snake; nevertheless, previous studies have only reported its distribution. The aim of the present study was to analyze characteristics of the dice snake population along the Vrbanja River. Animals were processed during 2011 throughout their activity period. In total, 199 individuals of all ages were collected. We observed substantial differences in numbers of animals captured in different habitat types classified according to the level of anthropogenic influence. Unexpectedly, the largest number of snakes was captured in the zone with the highest anthropogenic influence, while the smallest number was observed in the zone with no anthropogenic pressures. The above is probably connected with the observed greater number of their most common prey, as well as the absence of raptors in areas with human impact. In the surveyed area, dice snakes feed predominantly on cyprinid fishes, and their reproductive traits are in accord with literature data.

Distribution and hybridisation of barred and common grass snakes (Natrix helvetica, N. natrix) in Baden-Württemberg, South-western Germany

The distribution and hybridisation zone of the two grass snake species occurring in the German state of Baden-Württemberg are described, based on genetic data from maternally inherited mitochondrial DNA (mtDNA, up to 1983 bp) and biparentally inherited microsatellite DNA (13 loci). In agreement with previously published morphological evidence, the barred grass snake (Natrix helvetica) occurs in the Upper Rhine Valley and the Black Forest, while the common grass snake (N. natrix, ‘yellow lineage’) is distributed across the remaining, more eastern parts of Baden-Württemberg. Cline analyses across two transects running through the region of Karlsruhe and the Black Forest indicate that the hybrid zone is similarly narrow here as in the previously characterised stretch near Lake Constance. With respect to nuclear DNA, the Black Forest constitutes no impediment to gene flow in comparison with lowland regions (Karlsruhe, Lake Constance). However, on the eastern slope of the Black Forest, the abrupt replacement of mtDNA ofN. helveticaby that ofN. natrixindicates male-mediated gene flow and that the Black Forest represents a dispersal barrier for female grass snakes.

Movements and habitat choice of resident and translocated adult female Grass Snakes (Natrix natrix) during the egg-laying period

We used externally applied transmitters to study movements of female grass snakes (Natrix natrix) during the egg-laying period in a near-urban landscape in Sweden. Half of the studied snakes were residents while the other half were translocated individuals with no previous experience of the area. As predicted, resident females moved more goal-oriented and shorter distances than did translocated individuals. Habitat use did not differ between resident and translocated snakes; they were typically found in bushes, reeds, and tall vegetation. Habitat preference (use in relation to availability) showed that bushy habitats, tall grassy vegetation and reedbeds were over-used in proportion to availability, whereas forest and open grass lawns were used less than expected based on availability. Our study highlights the importance of preserving and restoring linear habitat components providing shelter and connectivity in conservation of grass snakes. We suggest that externally applied transmitters are a better option than surgically implanted ones in movement studies of grass snakes, and that translocation as a conservation method for snakes has drawbacks.

Movements and habitat choice of resident and translocated adult female Grass Snakes (Natrix natrix) during the egg-laying period

We used externally applied transmitters to study movements of female grass snakes (Natrix natrix) during the egg-laying period in a near-urban landscape in Sweden. Half of the studied snakes were r ...

Herpetofauna of the Kozubów Landscape Park

Abstract The research was conducted in 2016–2017 in the 6,613-ha Kozubów Landscape Park (KLP). It focused on the occurrence and distribution of amphibians and reptiles, the biology and phenology of selected species and the existing threats. The KLP, established in 1986, is located in the Nida Basin, covering the eastern part of the Wodzisławski Ridge. This area is characterised by diverse landscape features formed on a chalk substrate. A significant part of the KLP (48.8%) is covered by forests growing on the tops and slopes of loess hills intersected by valleys and gorges. Hornbeam forests and fragments of riparian forests have retained a semi-natural character. The steep, non-forested slopes with a southern and south-western exposure are overgrown by thermophilic xerothermic grasslands. Xerothermic plant communities show a relatively low species diversity, because the main type of substrate in this area is loess. Two nature reserves, Polana Polichno and Wroni Dół, are located within the KLP borders. The following amphibian species were found in the KLP: smooth newt (Lissotriton vulgaris L.), great crested newt (Triturus cristatus Laur.), European fire-bellied toad (Bombina bombina L.), common spadefoot toad (Pelobates fuscus Laur.), common toad (Bufo bufo L.), European green toad (Bufotes viridis Laur.), European tree frog (Hyla arborea L.), edible frog (Pelophylax esculentus L.), pool frog (Pelophylax lessonae Cam.), moor frog (Rana arvalis Nilss.) and common frog (Rana temporaria L.). Reptiles are represented by the sand lizard (Lacerta agilis L.), viviparous lizard (Zootoca vivipara Jacquin), slow worm (Anguis fragilis L.), grass snake (Natrix natrix L.), smooth snake (Coronella austriaca Laur.) and common European adder (Vipera berus L.). The study also included the phenology and reproductive biology of common toad and common frog. Major threats to the herpetofauna are posed by grass burning. Unfavourable changes include decreasing water levels and drying out of water bodies.

Neutralization of the lethality of the venom of Dendroaspis polylepis (black mamba) in mice by two polyvalent antivenoms used in Kenyan hospitals: Results of a 2009–2011 study

Abstract The black mamba is a common snake in Sub-Saharan Africa, a region with a high burden of snakebite envenoming. Differences in the composition and toxicity of the venom of this snake as one moves from one region to another within Sub-Saharan Africa, and the variations in manufacturing protocols by different antivenom producers may result in antivenom products of unknown efficacy. This variability may compromise the management of venomous snakebite in the region including those of the black mamba. Therefore, testing the antidotal efficacy of the antivenoms indicated for black mamba venom is warranted. The aim of the present study was to determine the efficacy of two antivenoms routinely used in some hospitals in Kenya between 2009 and 2011. The moving average interpolation method of Weil was used to determine the acute intraperitoneal (i.p) median lethal dose (LD50) of black mamba venom in mice. Symptoms of envenomation and the effects of the venom on hematological parameters were observed. The antidotal efficacy of the two polyvalent antivenoms (antivenom I and II) was then tested against the acute i.p. LD50 of black mamba venom. The acute i.p. LD50 of the whole venom of black mamba in mice was found to be 0.341 mg/kg. Antivenom I afforded 80% protection to mice experimentally envenomed with a 3 LD50 dose of black mamba venom while antivenom II afforded 60% protection to mice experimentally envenomed with a 3 LD50 dose of black mamba venom. Additionally, antivenom II also afforded 40% protection to mice experimentally envenomed with a 4 LD50 dose of black mamba venom. Analgesia, weakness, and altered respiration were observed as neurotoxic symptoms. The LD50 of black mamba venom in mice by the intraperitoneal route is low. Moreover, the data also suggests that the antivenoms tested during the study period had varying efficacy in neutralizing black mamba envenomation in mice.

SAT-158 RENAL TUBULAR DYSFUNCTION, COAGULATION DISTURBANCES AND NOVEL BIOMARKES IN ACUTE KIDNEY INJURY DUE TO SNAKEBITES

Acute kidney injury (AKI) following snakebite is a community-acquired entity, very frequent in developing countries. Bothrops genus is a large group of pit vipers (Lance-Headed) which are the most common snakes in Latin America. To evaluate the pathogenic mechanisms associated with Bothrops venom nephrotoxicity, we assessed the urinary and blood samples of patients after hospital admission because Bothrops erythromelas snakebite.

Herpetofauna of the Pieprzowe Mountains Nature Reserve and adjacent areas

Abstract The study was focused on determining the sites of amphibian and reptile occurrence in the Pieprzowe Mountains Nature Reserve (area 18.01 ha) and adjacent areas (total area 58.81 ha). The investigations also involved the biology of breeding in the selected species, as well as determining threats and protection measures. Situated in the eastern part of the Świętokrzyskie Voivodeship, the steppe-like Pieprzowe (Pepper) Mountains Nature Reserve was established in 1979. Its aim is to protect xerothermic assemblages inhabited by many species of rare plants including the largest European aggregation of roses growing wild. The area is located on a steep, sometimes rugged escarpment, which is part of the Vistula River erosional margin. The escarpment exposes Cambrian black pepper-like shales. The slope base is overgrown by a narrow belt of willow thickets. Above occur assemblages of xerothermic thickets with a few trees. The highest parts of the nature reserve are overgrown with xerothermic grasslands with the prevalence of feathergrass steppe (Festuco-Stipion class). The reserve is surrounded by riparian forests, waterlogged meadows and reservoirs of the Vistula former riverbed, the largest of which is an oxbow lake (5.16 ha). The following species were documented in 2016-2017: smooth newt Lissotriton vulgaris L., great crested newt Triturus cristatus Laur., European fire-bellied toad Bombina bombina L., common toad Bufo bufo L., European green toad Bufotes viridis Laur., European tree frog Hyla arborea L., edible frog Pelophylax esculentus L., pool frog Pelophylax lessonae Cam., marsh frog Pelophylax ridibundus Laur., moor frog Rana arvalis Nilss., common frog Rana temporaria L., sand lizard Lacerta agilis L., grass snake Natrix natrix L. and common European adder Vipera berus L. The studies were focused on biology of breeding and phenology in common toad and common frog. The main threats posed on herpetofauna include: human presence, littering, fire raising and changes of water balance. © IOŚ-PIB

Herpetofauna of the Podkielecki Landscape Protection Area

Abstract The study was conducted in 2016-2017 in the Podkielecki Landscape Protection Area (area 26,485 ha). It was focused on the occurrence and distribution of amphibians and reptiles, the biology of the selected species and the existing threats. Established in 1995, the Podkielecki Landscape Protection Area surrounds the city of Kielce from the north, east and south-east, and adjoins several other protected areas. It covers the western part of the Świętokrzyskie Mountains (part of the Klonowskie and Masłowskie ranges) and the southern part of the Suchedniów Plateau. The studied area is mostly covered by forest and thicket communities (48.1%) and farmlands (39.9%), followed by built-up areas (7.8%), industrial areas (0.5%), roads and railways (2.7%), and surface water bodies (1%). The protected area is developed mainly on Palaeozoic rocks, including Cambrian and Ordovician sandstones, Silurian and Carboniferous shales, and Devonian marls. Podzolic soils predominate among soils. The largest rivers include Lubrzanka, Czarna Nida, Bobrza and Belnianka. There are no natural lakes within the PLPA limits, and the largest artificial reservoirs include the Cedzyna Reservoir, Morawica Reservoir, Suków Sandpit and two sedimentation reservoirs of the Kielce Power Plant. The area includes 2 nature reserves: Barcza and Sufraganiec. The following amphibian species were recognised during the investigations within the borders of the studied area: alpine newt Ichthyosaura alpestris Laur., great crested newt Triturus cristatus Laur., smooth newt Lissotriton vulgaris L., European fire-bellied toad Bombina bombina L., common spadefoot toad Pelobates fuscus Laur., common toad Bufo bufo L., natterjack toad Epidalea calamita Laur., European green toad Bufotes viridis Laur., European tree frog Hyla arborea L., pool frog Pelophylax lessonae Cam., edible frog Pelophylax esculentus L., marsh frog Pelophylax ridibundus Pall., moor frog Rana arvalis Nilss., and common frog Rana temporaria L. The reptiles were represented by sand lizard Lacerta agilis L., viviparous lizard Zootoca vivipara Jacquin, slow worm Anguis fragilis L., grass snake Natrix natrix L. and common European adder Vipera berus L. The study also included the phenology and breeding biology of the common toad and common frog. The most crucial herpetofauna conservation problems identified here include amphibians killed on roads by vehicles. The study area is intersected by very busy roads, in particular: European route no. E77, national roads nos. 73, 74 and S74, and regional roads nos. 745, 750 and 764. For this reason, future road reconstruction projects should consider the assembly of various crossing roads for wildlife, particularly on the 600 m long section of national road no. 74 near Cedzyna Reservoir. Other threats include illegal waste dumping, pollution of surface waters, fire setting, overgrowing and desiccation of small water bodies. © IOŚ-PIB

The loss of sexual size dimorphism in urban populations of a widespread reptile, the European grass snake Natrix natrix.

The loss of sexual size dimorphism in urban populations of a widespread reptile, the European grass snake Natrix natrix.

A long-term study of a snake community in north-western Tuscany (central Italy): population structure and density patterns

We analysed a snake species community of a Mediterranean 0.2 ha ecotonal area during a 21 year time span, monitoring two colubrid and one viperid snake species. We carried out analyses in seven years (1997, 1999, 2002, 2004–2005, 2016–2017) that had similar sampling efforts and, in the last two years of short-term monitoring, we applied a recently proposed monitoring protocol of the Italian Environment Ministry. In total, we captured 172 distinct individuals, 61 whip snakes (Hierophisviridiflavus), 26 barred grass snakes (Natrixhelvetica) and 85 asp vipers (Viperaaspis). Regarding the long-term monitoring period, whip snakes were captured on average about nine times per year, grass snakes were captured four times per year and asp vipers were found 12 times per year. Captures decreased in whip snakes, while increased in grass snakes and remained constant in asp vipers. In 2016 and 2017, we captured 10 whip snakes, 19 grass snakes and 31 asp vipers. Density estimates of snake species (0.5 H.viridiflavus/ha, 0.3 N.helvetica/ha and 0.7 V.aspis/ha) differ, to a certain extent, from published results for some other areas of central, northern and western Europe, perhaps depending on the approach applied for habitat suitability estimation. The average body size between two years differed neither for whip snakes nor for grass snakes, but it decreased significantly in asp vipers.

Do different diets affect oxidative stress biomarkers and metal bioaccumulation in two snake species?

In this study we examined possible differences in heavy metal accumulation and oxidative stress parameters in the liver and muscle of two semi-aquatic snakes: grass snake (Natrix natrix) and dice snake (N. tessellata), that inhabit the same environment but differ in prey diversity. The obtained results revealed some interspecies, inter-tissue, prey-snake and prey-prey differences in heavy metal concentrations. Grass snakes pray contained significantly higher concentrations of Al, Cr and Fe as compared to food of dice snakes. Both investigated snakes accumulated generally lower concentrations of metals than their prey, indicating that they are not at risk of contaminant biomagnification. A significant interspecies difference in accumulation was observed only for Cu and Mn concentrations. On the other hand, analysis of oxidative stress biomarkers showed clear differences between the investigated snake species and the two investigated tissues. The liver of grass snake had increased superoxide dismutase, glutathione reductase and glutathione-S-transferase activities in comparison to dice snake. In muscle, a reverse trend was observed for the activities of these three enzymes, as well as for glutathione peroxidase activity. The higher number of significant correlations observed between oxidative stress biomarkers and heavy metal concentrations in grass snake points to upregulation of the antioxidative system (AOS), which resulted in a lower TBARS concentration. Results show that while the investigated snake species did not differ significantly in the accumulated metals, their defense mechanisms were different. This reveals the complexity of the AOS and points to the cooperation of different AOS components in individuals from natural populations.