Detection of Serpentoplasma sp. (Apicomplexa: Haemohormidiidae) in dice snake (Natrix tesellata) (Colubridae: Natrix) in Azerbaijan.

The purpose of the research is a comparative analysis of the helminth fauna in dice snakes of the grey and black morph inhabiting the Lower Volga region. Materials and methods . A total of 32 grey and 41 black dice snakes Natrix tessellata from three habitats in the Astrakhan region, caught in 2004, 2005, and 2008, were examined using the method of complete helminthological dissection. The parasitological material was processed using standard methods. Statistical analysis was performed using the Shannon, Jaccard, Sorensen, Palia-Kovnatski dominance indices, and the Mann-Whitney criterion. Results and discussion . A comparative analysis of the helminth fauna in dice snakes of the grey and black morph was conducted. A total of 21 species of parasitic worms were found in dice snakes examined: Cestoda – 1, Trematoda – 11, Nematoda – 8, Acanthocephala – 1. All these species of helminths were found in grey dice snakes. In black N. tessellata , 18 species of parasites were recorded. Paralepoderma cloacicola, Camallanus lacustris and Centrorhynchus aluconis were found only in grey morph of the dice snake. The analysis of the total helminth infection in dice snakes of different morphs did not reveal any significant differences, as well as pairwise comparison of the infection of reptiles by common parasite species. It was found that the structure and dominance of parasites in the helminth fauna of grey and black N. tessellata differs. Comparison of the helminth fauna of grey and black dice snakes in both qualitative and quantitative terms showed a high degree of similarity. Analysis of the helminth species diversity in dice snakes of different morphs revealed that the diversity of the parasite fauna of grey and black N. tessellata is approximately at the same level. Similar structure of helminths in dice snakes of different colors indicates the similarity of their topical and trophic niches. Relatively high infection of grey dice snakes with helminths is probably due to differences in physiology. It was established that both morphs of N. tessellata take part in the formation of the helminth fauna of the dice snake.

Infections with blood parasites are common phenomenon in reptiles from all over the world. Apicomplexan are the majority of blood parasites that frequently occur with high levels of parasitaemia in the snakes. The aim of this study was to determine the presence of blood parasites in some snakes Guilan province in the North of Iran. A total of 51 specimens of three snake species were captured including 18 specimens of Natrix natrix, 30 of Natrix tessellata and three from Zamenis longissimus. Blood sampling was carried out from the caudal vein by insulin syringe. The blood smears were stained with Giemsa solution and examined by light microscopy for heamoparasites. We found one species of Hepatozoon sp. as well as two intra-erythrocytic structures that we referred them to Rickettsia and Serpentoplasma in the snakes. The Serpentoplasmawith small amoeboid shape only detected in N. tessellate. But the Rickettsia which is bigger in size and formed roughly spherical inclusions detected in both Natrix species. This finding of haemoparasites represents for the first time in these snakes.

ABSTRACTNon‐indigenous species can have strong impacts on biodiversity by affecting trophic relationships in their new environments. The piscivorous dice snake (Natrix tessellata) has been introduced to Geneva Lake, western Switzerland, where the endangered viperine snake (Natrix maura) is native. Local, dramatic declines in the viperine snake population might be associated with the appearance of the dice snake through dietary overlap between these 2 species, which mainly feed on bullhead (Cottus gobio). In response to this decline, a control program for dice snake was implemented in 2007 to reduce numbers of this introduced snake. In 2010, a new species of fish, the freshwater blenny (Salaria fluviatilis), which shares the same habitat as the bullhead, was introduced into Lake Geneva and has since reached high densities. We determined the impact of freshwater blenny on diet composition and body condition of dice snakes. In addition, we tested for effects of the control program on the body condition of dice snakes and viperine snakes. We collected 294 dice snakes between 2007 and 2013. Based on morphology and a genetic marker (cytochrome b gene), we determined the fish species contained in these snakes’ stomachs. We found a drastic switch in dice snake diet following the arrival of freshwater blenny, as consumption of bullhead declined by 68% and was replaced by the blenny. In addition, the body condition of dice snakes increased significantly after the arrival of freshwater blenny. The body condition of both snake species was positively correlated with the number of dice snakes removed from the study area. This finding has important implications concerning the conservation of the endangered viperine snake, and suggests that the control program of dice snakes should be continued. © 2014 The Wildlife Society.

Ophidiomycosis (formerly snake fungal disease) is an emerging disease in snakes caused by the fungal pathogen Ophidiomyces ophidiicola (Oo). The disease is characterized by skin lesions that can range from mild to severe with associated fatalities documented. Subclinical infections have also been described presenting a wide variability of the impact Oo has on the host. In wild snakes, infections have most often been documented in North America, but increasing numbers of reports are becoming available from other parts of the world, including Europe. While monitoring dice snake (Natrix tessellata) populations in 2018 at Schleuse Hollerich/Lahn, a nature reserve in Germany, three dice snakes were observed with cutaneous granulomas. One year later, snakes with granulomas were also observed, and two dice snakes were captured and examined. Fungal hyphae were found in skin biopsies of the lesions, and Oo was detected by PCR in the shed skin from one of the snakes. After shedding, the snakes appeared clinically healthy and were released back to the location at which they had been found. This is the first report of histologically confirmed ophidiomycosis in dice snakes and the first confirmed report of ophidiomycosis in a wild snake in Germany.

Abstract. Dice snakes (Natrix tessellata, Laurenti, 1768) inhabit oligohaline and brackish waters along the Bulgarian Black Sea coast, where they often forage at sea. Under these conditions, this species should tolerate highly variable blood plasma sodium concentrations for extended time periods, but the effect of high sodium concentrations to blood cell morphology and physiology is largely unknown. In this experiment, we placed adult dice snakes in waters with different salinity for 84 h, representing the three typical saline concentrations in which dice snakes live and forage: 0.2 ‰ NaCl, fresh water, 16 ‰ NaCl, Black Sea water and 36 ‰ NaCl, World Ocean water. We collected blood through cardiocentesis after exposure to each treatment and used Giemsa's solution for staining the formed elements. We registered numerous nuclear abnormalities (nuclear buds, lobes and blebs) in the blood cells of all investigated specimens. In the snakes placed in the waters with high saline concentration (16 and 36 ‰ NaCl) we found numerous cells with ruptured membranes. These snakes also showed increased mitochondrial activity compared to those in fresh water (1.85 and 2.53 times higher, respectively). Our data suggest that even though dice snakes show a remarkable tolerance to waters with increased salinity, prolonged exposure to it induces significant physiological stress in N. tessellata, which poses a clear limit for their ability to stay in the sea for a long time.

The present study was designed to evaluate the responsiveness of modulation of glial fibrillary acidic protein (GFAP) content and its fragmentation in the snake brain as a biomarker of local industrial pollution of aquatic ecosystems. Despite GFAP being a well known cytoskeleton marker of astrocytes’ reactivity in the brain of vertebrates, its expression in the snake brain remains insufficiently described. The GFAP expression and its fragmentation were detected using the immunoblot method in the snake brain. ROS level was determined with dichlorofluorescein diacetate fluorescence. The content of the glial fibrillary acidic protein (GFAP) of filament (cytoskeleton) and soluble (cytosol) fractions in the brain of dice snake Natrix tessellata from three ecosystems with different rates of industrial pollution were studied (two polluted and one clean control site). Characteristic increase in GFAP fragmentation was noted for the snakes from both the researched polluted sites. Significant increase in the content of the GFAP cleaved polypeptide fragments induced by industrial pollution exposure was confirmed in the snakes’ brains. Meaningful GFAP fragmentation was determined in snake brain astrocytes as an increase in cleaved fragments of 47–35 kDa molecular weight for both soluble and cytoskeletal GFAP fractions. We found significant abnormality in the ratio of the GFAP soluble fraction to the cytoskeletal one in contaminant-exposed dice snakes. It should testify to significant metabolic disturbance in nerve cells of the dice snakes. Furthermore, growth of reactive oxygen species level as the main cause of oxidative stress was determined in brains of the snakes exposed to environmental toxicity. Thus, astrocyte cytoskeleton disorders are associated with pollutant-induced redox imbalance in the snake brain. Despite the limited data on glial cell biology in the reptilian brain, the observed results prove that snake astrocytes can respond to the environmental toxicity using typical astroglial response. The presented results evidence that monitoring of molecular characteristics of glial cytoskeleton in dice snakes could be used as reliable biomarker of neurotoxicity and adverse effects of industrial pollution. Further studies are required to elucidate the role of astrocyte cytoskeleton in the response against neurotoxic contaminants.

Effects of the urban environment on the developmental stability, size and body condition of dice snakes (Natrix tessellata) living in artificial lakeside habitats

Based on a two-year monitoring, we analysed the distribution of dice snake populations in the Canton of Ticino (Switzerland). Imperfect detection was taken into account in order to avoid underestimation of the distrub- tion range and hence overestimating the species threat status: we therefore used a model based on a mark-recapture- like approach to estimate detection probability, which was 61.2% (± 6.8%; standard error), and site occupancy, which was 78.0% (± 7.9%). Detection probability depended on habitat characteristics (tree cover and naturalness of the streams and lake shores) while occupancy was best predicted by the number of previous dice snake records at a site. We observed local decline or extinction of some small populations located on secondary streams, apparently because of habitat deterioration. However, populations located on lakes (Lugano, Maggiore) and main rivers (Ticino, Brenno, Maggia, Vedeggio and Tresa) showed no signs of decline and rather high densities. Therefore, the status of Natrix tes- sellata in Ticino should be considered as stable. The endangered status reported by the Swiss Red List for these spe- cies is adequate because of the small area occupied at national level (IUCN criteria B2a, B2b (iii, iv)) and vulnerability of freshwater ecosystems. A specific action plan in favour of the conservation of dice snakes populations in Ticino, Switzerland, will now be based on the collected data.

Aspects of the predator–prey relationship between dice snake,Natrix tessellataand gobiid fish infected withEustrongylides excisuswere studied in Lake Sinoe, Romania. A population of snakes residing here shows a high prevalence of subcutaneous larvae of this nematode. The hypothesis of the altered motility in infected fish leading to increased depredation by snakes was tested by comparing gobiids collected from dice snakes with gobiids caught via electrofishing. Out of a total of seven identified gobiid species, three were used for analysis: syrman gobyNeogobius syrman, mushroom gobyNeogobius eurycephalus, and round gobyNeogobius melanostomus. No significant differences in prevalence and intensity ofE.excisusinfection were found between fish caught by snakes and those obtained by electrofishing. However, significantly higher abundance ofE.excisuslarvae in fish caught by snakes was reported. These findings suggest limited influence of the presence ofE.excisuslarvae in studied gobiids regarding their susceptibility to predation by dice snakes.

Predation exerts a significant selection pressure on prey, shaping a multitude of traits that serve as antipredator defences. In turn, natural selection could favour combinations of antipredator defences with synergistic effects that enhance prey survival. An especially interesting antipredator defence is death feigning (DF), present in a wide variety of taxa and usually characterized by the prey lying motionless often along with defecation, musking, and auto-haemorrhaging. All these aspects of DF should work in conjunction with one another, intensifying the overall effect of the display and in turn facilitating quicker escape. To confirm this hypothesis, we tested 263 dice snakes (Natrix tessellata) directly in the field. We noted the occurrence of smearing faeces and musk and autohaemorrhaging and we measured the duration of DF, expecting to see a negative association between the occurrence of these behaviours and the duration of DF. Our results affirm our hypothesis: dice snakes that smeared themselves in musk and faeces before DF and had auto-haemorrhaging during DF spent significantly less time in DF. Our results highlight the functional integration of antipredator behaviors across different phases of predator-prey interactions, emphasizing the need for future research to prioritize studying the sequential display of behaviors.

The effects of waterborne metals in water on the activities of blood copper-zinc superoxide dismutase (CuZnSOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), glutathione-S-transferase (GST), and acetylcholinesterase (AChE), and on the concentrations of total glutathione (GSH) and lipid peroxides (TBARS) in the blood of dice snakes (Natrix tessellata) caught in Obedska Bara, Sebia (control area), with snakes caught in Pancevacki Rit, a contaminated area in Serbia were examined. The activities of CAT, GSH-Px, GR and AChE, and the concentration of TBARS were significantly decreased, while GST activity and GSH concentration were significantly increased in snakes from the contaminated area compared to specimens from the control area. Significantly increased concentrations of Al, As, B, Ba, Ca, Cu, Fe, K, Li, Mn, Na, Ni and Zn in the water at the contaminated area as compared to control area were detected. The metals Ag, Bi, Cd, Co, Hg, In and Tl were not observed in any of the localities. Cr, Mo and Pb were not detected at the control area but were observed at the contaminated area. The concentrations of Sr were similar at both sites. The concentration of Mg was 2-fold higher at the control site than at the contaminated area. The obtained results show that most of the investigated blood biomarkers correlate with concentrations of metals present in the environment. These findings suggest that dice snakes are sensitive bioindicator species for monitoring the effects of increased metal concentrations in the environment.

ContextHuman-induced landscape modification, such as urbanization, creates new environments that can have adverse effects on flora and fauna, posing threats to biodiversity. Understanding how reptiles respond to urbanization is crucial, especially in light of their ongoing population declines.ObjectivesWe examined the influence of landscape-scale and local-scale urbanization features on the abundance of an aquatic snake species. Our investigation focused on dice snakes (Natrix tessellata) inhabiting a lake with a heavily urbanized shoreline.MethodsWe conducted visual encounter surveys at 25 study sites during the activity period of dice snakes around Lake Balaton in Hungary. We measured both landscape-scale and local-scale variables, including urban land use cover, vegetation cover, road cover, distance of main roads and city size, emergent vegetation cover and the area of artificial rock and concrete shoreline protection structures. We analysed snake survey data using N-mixture models to estimate abundance and examine relationships with landscape-scale and local-scale variables.ResultsUrban land use cover, road cover, the proximity of main roads and the extent of artificial rock and concrete shoreline protection structures positively affected the abundance of snakes. These findings imply that urban habitats may offer new ecological opportunities for dice snakes.ConclusionsThe findings of this study indicate that both landscape-scale and local-scale human-induced landscape modifications may have a positive impact on the abundance of urban snakes. Taken together, our findings suggest that urbanization is a complex phenomenon, affecting species at different levels and with subtle effects.

Predation exerts a significant selection pressure on prey, shaping a multitude of traits that serve as antipredator defences. In turn, natural selection could favour combinations of antipredator defences with synergistic effects that enhance prey survival. An especially interesting antipredator defence is death feigning (DF), present in a wide variety of taxa and usually characterized by the prey lying motionless often along with defaecation, musking and autohaemorrhaging (AH). All these aspects of the DF display should work in conjunction with one another, intensifying the overall effect of the display and in turn facilitating quicker escape. To confirm this hypothesis, we tested 263 dice snakes (Natrix tessellata) directly in the field. We noted the occurrence of smearing faeces, musk and AH, and we measured the duration of DF, expecting to see a negative association between the occurrence of these behaviours and the duration of DF. Our results affirm our hypothesis: dice snakes that smeared themselves in musk and faeces prior to DF and had AH during DF spent significantly less time in DF. Our results highlight the functional integration of antipredator behaviours across different phases of predator-prey interactions, emphasizing the need for future research to prioritize studying the sequential display of behaviours.

Golem Grad is a small island situated in montane Prespa Lake, North Macedonia. Rock crevices, shrubs, and trees provide microhabitats favorable to reptiles. Ruins of old buildings from past centuries offer abundant shelters. Prespa Lake ecosystems have been spared from industrial agriculture and urbanization, and, for these reasons, Golem Grad hosts large populations of Hermann Tortoise (Testudo hermanni), Common Wall Lizard (Podarcis muralis), Nose-horned Viper (Vipera ammodytes), and amphibious Dice Snake (Natrix tessellata). These species also occur on the nearby mainland and in Eastern Europe. Compared with continental populations, the insular vipers are dwarf while insular Dice Snakes exhibit a trend to gigantism. Low-quality food resources (e.g., centipedes) may limit the growth and fecundity of vipers, whereas Dice Snakes benefit from high-quality prey (large schools of fish) that may promote large body size and sustain large populations. Hence, both dwarf and very large snake populations cohabit on Golem Grad.

Using two mitochondrial DNA fragments and 13 microsatellite loci, we examined the phylogeographic structure and taxonomy of two codistributed snake species (Natrix natrix,N. tessellata) in their eastern distribution area, with a focus on Turkey. We found evidence for frequent interspecific hybridization, previously thought to be extremely rare, and for backcrosses. This underscores that closely related sympatric species should be studied together because otherwise the signal of hybridization will be missed. Furthermore, the phylogeographic patterns of the two species show many parallels, suggestive of a shared biogeographic history. In general, the phylogeographies follow the paradigm of southern richness to northern purity, but the dice snake has some additional lineages in the south and east in regions where grass snakes do not occur. For both species, the Balkan Peninsula and the Caucasus region served as glacial refugia, with several mitochondrial lineages occurring in close proximity. Our results show that the mitochondrial divergences in both species match nuclear genomic differentiation. Yet, in the former glacial refugia of grass snakes there are fewer nuclear clusters than mitochondrial lineages, suggesting that Holocene range expansions transformed the glacial hotspots in melting pots where only the mitochondrial lineages persisted, bearing witness of former diversity. On the other hand, the deep mitochondrial divergences inN. tessellataacross its entire range indicate that more than one species could be involved, even though lacking microsatellite data outside of Turkey prevent firm conclusions. On the contrary, our microsatellite and mitochondrial data corroborate thatN. megalocephalais invalid and not differentiated from sympatric populations ofN. natrix. For Cypriot grass snakes, our analyses yielded conflicting results. A critical assessment of the available evidence suggests thatN. natrixis a genetically impoverished recent invader on Cyprus and taxonomically not distinct from a subspecies also occurring in western Anatolia and the southern Balkans. Based on combined mitochondrial and nuclear genomic evidence we propose that for grass snakes the following subspecies should be recognized in our study region: (1)Natrix natrix vulgarisLaurenti, 1768, southeastern Central Europe and northern Balkans; (2)Natrix natrix moreotica(Bedriaga, 1882), southern Balkans, western Anatolia, and Cyprus; and (3)Natrix natrix scutata(Pallas, 1771), eastern Anatolia, Caucasus region, Iran, northeastern distribution range (from eastern Poland and Finland to Kazakhstan and the Lake Baikal region). Thus,Natrix natrix cypriaca(Hecht, 1930) becomes a junior synonym ofN. n. moreoticaandNatrix natrix persa(Pallas, 1814) becomes a junior synonym ofN. n. scutata. Due to insufficient material, we could not resolve the status ofNatrix natrix syriaca(Hecht, 1930) from the Gulf of İskenderun, southeastern Turkey.