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New review of medicinal compounds in toad secretions compiled

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New review of medicinal compounds in toad secretions compiled

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Skin and glandular secretions from the cane toad, Rhinella marinus, have long been used by practitioners of traditional medicine to cure a wide range of ills. Researchers have now compiled a list of all of the chemicals known from the amphibian family Bufonidae, of which it is one of the most common members.
Credit: Brian Gratwicke

https://www.sciencedaily.com/releases/2017/01/170127113042.htm

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Εcological risk assessment constitutes a technological advance as well as a contribution to ecotoxicology practical goals - Business plan

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Εcological risk assessment constitutes a technological advance as well as a contribution to ecotoxicology practical goals - Business plan

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-General methods to biomonitor (use of organisms to monitor contaminants and to imply possible effects to biota or sources of toxicants to humans and apply biomarkers (cellular, tissue, body fluid, physiological or biochemical changes in individuals that are used quantitatively during biomonitoring to imply presence of significant pollutants or as early warning systems for imminent effects)
- Chromosome aberration assay:  structural aberrations such as fragments or intercalations and numerical aberrations
- Micronucleus assay :  Amphibian micronucleus procedure has been standardized.
- A real-time flow-through system, which measures in situ contaminantinduced fluorescence in transgenic amphibians larvae immersed in water sample. The amplification of DNA by the Polymerase Chain Reaction technique enabled the detection of mutations at specific sites and the development of electrochemical DNAbased biosensors.

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The two HerpetoAreas are Attica and Crete, in the country of Greece. We chose some common species to study, like the snake Zamenis situla and that indicates that there are similar physiological and ecological characteristics among species. However, there might be some ecological differences as well, depending on the different habitats presented in each area. Additionaly, different species among reptiles and amphibians might share common physiological traits, but they can also respond in a different way in a similar environment.
https://padlet.com/antonis_35/lgju3uso4t2k

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The similarity of our padlets lies in the fact that we are in the same country, Greece, but we have focused on different regions, Attica and Crete. We share similar habitas, like mountains and lakes, but there are no endemic species in Attica, in contrary to Crete.
https://padlet.com/antonis_35/lgju3uso4t2k

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There are threats in both HerpetoAreas, with some differentiations, but wildlife faces dangers, even extinction, in both cases.
https://padlet.com/antonis_35/lgju3uso4t2k

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Cretan Water Frog (scient. Pelophylax cretensis or Rana cretensis

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Cretan Water Frog (scient. Pelophylax cretensis or Rana cretensis

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Is one of the three endemic species of amphibians of Greece, which is found only on the island of Crete.

Unfortunately, in recent years its population has declined dramatically. One of the most serious threats is the introduction of the American Bullfrog (Rana catesbeiana). Some years ago, someone freed bullfrogs in Agia Lake, resulting in the extinction of the local endemic frog.

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The Historical Speciation of Mauremys Sensu Lato

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The Historical Speciation of Mauremys Sensu Lato

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Inconsistent results between gene flow assessment and phylogenetic analysis revealed the hybrid origin of M. mutica (Southeast Asian). Here ancestral area reconstruction and interspecific gene flow level assessment were first used to explore species origins and evolution of Mauremys sensu lato, which provided new insights on this genus.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0144711

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https://www.hylawerkgroep.be/jeroen/index.php?id=49

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Like all Cretan snakes, the leopard snake rarely gets much above one metre in length and is generally found in sunny areas with some cover, such as a dry-stone wall. Houses also provide the kind of shelter they require, obviously lending to their northern Greek name. They do not, however, object to a swim and I have found them several times in the pools of Aposolemi between Analipsis and Gouves. Should you come across one, it may well rattle its tail in an attempt to scare you off and it is capable of striking and delivering a nip to the fingers of those who try to pick it up. Although the leopard snake does eat birds and small lizards, its diet consists mainly of rodents and their young – a natural control which is important and far preferable, to my mind, to laying out poison!

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Habitat Destruction | Pollution & Pesticides | Climate Change | Invasive Species  | Over-Harvesting | Infectious Diseases

https://www.savethefrogs.com/d/threats/index.html

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Europeans alone consumed roughly 120 million frogs per year in the 1990's. The harvesting of amphibians for the food trade is often unregulated, and in many underdeveloped countries, such as Thailand, is likely a primary contributor to amphibian declines. Even in countries where the import/export of endangered species is controlled, there are virtually no protocols in place to ensure that diseased amphibians do not get transported. Bullfrogs (Rana catesbeiana) are commonly farmed and transported worldwide. They are known carriers of the amphibian chytrid fungus (Batrachochytrium dendrobatidis) and thus are likely to be primary contributors to the global spread of chytridiomycosis, a disease that has decimated amphibian populations worldwide. In a recent study, 62% of the captive-raised bullfrogs sampled in shops in New York, Los Angeles and San Francisco were infected with the chytrid fungus! These three cities alone import over five million amphibians each year. Bullfrogs are also quite adept at establishing populations in areas to which they are introduced. They are large and compete with native amphibians for food and shelter, making them a harmful invasive species when they are outside their natural range (the eastern United States). Read more about over-harvesting here.

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The Amphibian Extinction Crisis - what will it take to put the action into the Amphibian Conservation Action Plan?

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The Amphibian Extinction Crisis - what will it take to put the action into the Amphibian Conservation Action Plan?

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The current mass extinction episode is most apparent in the amphibians. With approximately 7,000 species, amphibians are dependent on clean fresh water and damp habitats and are considered vulnerable to habitat loss (deforestation), changes in water or soil quality and the potential impacts of climate change, and in addition many species are suffering from an epidemic caused by a chytrid fungus. Because of their sensitivity and general dependence on both terrestrial and aquatic habitats they are often regarded as indicators of the health of the environment.

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Exhibition Halls of Natural History Museum of Crete, University of Crete

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http://www.herpetofauna.gr/index.php?module=narticle&page=read&id=24

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Traffic noise affects communication behaviour in a breeding anuran, Hyla arborea

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Traffic noise affects communication behaviour in a breeding anuran, Hyla arborea

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Modern human societies generate new patterns of noise that may affect acoustic communication in many animal species. Whilst animals have evolved several mechanisms to cope with natural background noise, the rapid increase of anthropogenic alteration of acoustic environment could challenge the potential for adjustments of communicative systems. Because acoustic communication is involved in crucial behaviours, noise pollution can be particularly detrimental in affecting breeding success or survival. I investigated the impact of traffic noise on acoustic communication in a tree frog by way of an experimental approach using noise playback. Traffic noise triggered a decrease of the males’ calling activity, with males being more affected when noise amplitude increased. Additionally, the males’ social situation (calling in chorus versus alone) exerted a strong influence on sensitiveness to noise. Males were only weakly affected by noise pollution when calling in a chorus situation, probably because they were more stimulated and because traffic noise emergence was lower. Moreover results showed that in response to noise playback, males are not able to adjust their temporal or frequency call structures to increase efficiency of the information transfer. Understanding species’ ability to adapt their communicative systems to cope with human-made noise constitutes an important contribution to wildlife conservation.

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Traffic noise affects communication behaviour in a breeding anuran, Hyla arborea

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Modern human societies generate new patterns of noise that may affect acoustic communication in many animal species. Whilst animals have evolved sever...

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Physiological Color Change in the Green Treefrog: Responses to Background Brightness and Temperature

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Physiological Color Change in the Green Treefrog: Responses to Background Brightness and Temperature

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We found that (1) males
are generally darker than females but the sexes exhibit similar color change
responses, (2) treefrogs become lighter on brighter backgrounds, (3) treefrogs
become lighter at higher temperatures, and (4) there is a background-by-temperature interaction such that color change responses to one variable depend on
the level of the other. Our results suggest that color change may function both
in predator avoidance and in thermoregulation or water balance. However, further investigations of color change responses to differently hued backgrounds,
of the magnitude and biological significance of color-induced changes in body
temperature and rates of evaporative water loss, and of color change in freeranging animals are needed

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The results suggest control of body temperature in Hyla arborea by microhabitat selection, with shaded areas selected to avoid potentially critical high temperatures during sunny weather. However, occasional basking in open locations, even during hot weather suggests an attempt to elevate body temperature.

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Hypernatremia in Dice Snakes (Natrix tessellata) from a Coastal Population: Implications for Osmoregulation in Marine Snake Prototypes

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Hypernatremia in Dice Snakes (Natrix tessellata) from a Coastal Population: Implications for Osmoregulation in Marine Snake Prototypes

# data[].attributes.body
The widespread relationship between salt excreting structures (e.g., salt glands) and marine life strongly suggests that the ability to regulate salt balance has been crucial during the transition to marine life in tetrapods. Elevated natremia (plasma sodium) recorded in several marine snakes species suggests that the development of a tolerance toward hypernatremia, in addition to salt gland development, has been a critical feature in the evolution of marine snakes. However, data from intermediate stage (species lacking salt glands but occasionally using salty environments) are lacking to draw a comprehensive picture of the evolution of an euryhaline physiology in these organisms. In this study, we assessed natremia of free-ranging Dice snakes (Natrix tessellata, a predominantly fresh water natricine lacking salt glands) from a coastal population in Bulgaria. Our results show that coastal N. tessellata can display hypernatremia (up to 195.5 mmol.l−1) without any apparent effect on several physiological and behavioural traits (e.g., hematocrit, body condition, foraging). More generally, a review of natremia in species situated along a continuum of habitat use between fresh- and seawater shows that snake species display a concomitant tolerance toward hypernatremia, even in species lacking salt glands. Collectively, these data suggest that a physiological tolerance toward hypernatremia has been critical during the evolution of an euryhaline physiology, and may well have preceded the evolution of salt glands.

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François Brischoux,

Yurii V. Kornilev

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Abstract

The widespread relationship between salt excreting structures (e.g., salt glands) and marine life strongly suggests that the ability to regulate salt balance has been crucial during the transition to marine life in tetrapods. Elevated natremia (plasma sodium) recorded in several marine snakes species suggests that the development of a tolerance toward hypernatremia, in addition to salt gland development, has been a critical feature in the evolution of marine snakes. However, data from intermediate stage (species lacking salt glands but occasionally using salty environments) are lacking to draw a comprehensive picture of the evolution of an euryhaline physiology in these organisms. In this study, we assessed natremia of free-ranging Dice snakes ( Natrix tessellata, a predominantly fresh water natricine lacking salt glands) from a coastal population in Bulgaria. Our results show that coastal N. tessellata can display hypernatremia (up to 195.5 mmol.l −1) without any apparent effect on several physiological and behavioural traits (e.g., hematocrit, body condition, foraging). More generally, a review of natremia in species situated along a continuum of habitat use between fresh- and seawater shows that snake species display a concomitant tolerance toward hypernatremia, even in species lacking salt glands. Collectively, these data suggest that a physiological tolerance toward hypernatremia has been critical during the evolution of an euryhaline physiology, and may well have preceded the evolution of salt glands.

Citation: Brischoux F, Kornilev YV (2014) Hypernatremia in Dice Snakes ( Natrix tessellata) from a Coastal Population: Implications for Osmoregulation in Marine Snake Prototypes. PLoS ONE 9(3): e92617. https://doi.org/10.1371/journal.pone.0092617

Editor: Ulrich Joger, State Natural History Museum, Germany

Received: November 5, 2013; Accepted: February 25, 2014; Published: March 21, 2014

Copyright: © 2014 Brischoux and Kornilev. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: Funding was provided by the CNRS (France). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Living in seawater entails physiological consequences such as water loss and salt gain, and coping with these constraints represents one of the principal challenges of secondarily marine vertebrates [1]. Accordingly, marine tetrapods (i.e., mammals, birds, turtles, snakes, lizards and crocodiles) display specific adaptations related to the maintenance of osmotic balance. For instance, marine mammals have specialized nephrons which allow highly concentrated urine [2]. Although marine reptiles lack the ability to excrete excess salt in urine, they have evolved salt glands that secrete concentrated salt solution [3], [4].

The widespread relationship between marine life and presence of specific salt-excretory structures, found across very different taxa, strongly suggests that the ability to excrete excess salt has been critical during the invasion of marine environments by tetrapods. However, as with most evolutionary processes, transitional steps are missing and are seldom represented by fossil remains [5]. In addition, crucial characteristics such as physiology and/or behaviour do not print well within the fossil records [5]. Yet, some research works have proposed scenarios of the evolution of an euryhaline physiology during the transition to marine life [6], [7], [8]. For instance, Dunson and Mazzotti [6] have proposed four successive steps that should ultimately lead to an efficient maintenance of the osmotic balance. The first step consists of a primary reliance on behavioural osmoregulation (e.g., frequent obligate fresh water drinking [9]). The second step involves a reduction in salt gain and water loss through permeable surfaces [10], [11], [12]. The third and fourth steps include the evolution of rudimentary salt secreting features and their subsequent development [4], which would ultimately allow exploiting more saline, thus larger, oceanic areas [13].

Clearly, these successive stages would ultimately allow organisms to progressively become emancipated from regular access to fresh water, and thus to thrive in saline environments. Likely, this has led to the conclusion that marine tetrapods could maintain their water balance without consuming fresh water [14], [15]. However, recent investigations have challenged this paradigm. Specifically, the most detailed studies performed on marine snakes have shown that species having a functional salt gland cannot equilibrate their hydromineral balance without access to fresh water [12], [16]. Dehydration in seawater has been shown to occur in amphibious sea snakes (Laticaudine sea kraits) as well as in fully marine species (Hydrophine sea snakes) [12], [16], [17]. In addition, elevated plasmatic sodium concentrations have been measured in various marine snake species [18]-[25]. These studies have led to the hypothesis that the development of a physiological tolerance to hypernatremia may have been an important feature of the evolution of marine snakes [25]. However, data gathered under experimental conditions show that fresh water species lacking salt glands (including coastal presumably salt tolerant species) rapidly accumulate large salt loads when acclimated in brackish and salt water [24], [26]. In most of these cases, the resulting hypernatremia was lethal [24], [26]. Taken together, these elements highlight the lack of information from groups thought to resemble transitional forms between the land and the sea (species lacking salt glands but occasionally using salty environments) to draw a comprehensive picture of the evolution of an euryhaline physiology in these organisms.

Snakes provide a suitable study system with which to clarify the steps that allowed coping with osmotic challenge [13]. Indeed, this lineage displays a unique gradient of habitat use which allows studying groups thought to resemble transitional forms between the land and the sea [13], [27]. Importantly, these transitional steps can be investigated at several phylogenetic scales along a gradient of habitat use [27]. Species that are salt tolerant, but imperfectly marine (i.e., lacking salt glands) represent a powerful opportunity to investigate the early steps of the evolution of an euryhaline physiology. In the current investigation, we examine such a study system. The European Dice snake ( Natrix tessellata) is a typical semi-aquatic fresh water natricine species that occurs over Eurasia (broadly from Italy to China [28]). Although this species relies primarily on fresh water bodies to forage for fish and amphibians, some populations are known to use, more or less extensively, brackish or saline habitats, thereby offering the possibility to investigate an intermediate step during the evolution to marine life. In this study we report natremia (plasma sodium concentration, an indicator of the osmotic challenge linked to marine life in snakes [25]) measured in free-ranging Dice snakes inhabiting a coastal ecotone between freshwater and the Black Sea in Bulgaria. In combination with a review of plasmatic sodium concentration of snakes, these results are discussed in the light of the secondary transition to marine life in tetrapods.

Materials and Methods

Ethics statement

All procedures were approved by French and Bulgarian regulations (Comité d'éthique Poitou-Charentes approval number CE2013-5 to FB; Ministry of Environment and water of Bulgaria permit to YVK: 298/09.03.2011).

Study species

Natrix tessellata is a medium-sized (up to 130 cm [29]) species with an extended Palearctic distribution: from central Europe to northern Egypt and east as far as north-western China [30], [31]. It is a typical semi-aquatic natricine foraging mainly for fish, and to a lesser extent for amphibians in streams, rivers, and lakes [28].

Although the vast majority of N. tessellata populations rely on fresh water bodies, few do occur in saline environments along the coasts of the Adriatic Sea [28], [32]-[35], the Ionian and Aegean Seas [36], the Black Sea ([37]-[40], this study) and the Caspian Sea [41], [42]. In most of these cases, N. tessellata occurs in brackish waters of lagoons, salt marshes and river mouths.

Study site

We surveyed a population of Dice snakes on the southern Bulgarian Black Sea coast, in the "Poda" Protected Area ( Fig. 1). The Poda wetland (1 km ²) consists of a coastal ecotone inserted between a large predominantly freshwater reservoir (Mandra Lake) and the Black Sea ( Fig. 1). Poda is mainly composed of an alternation of shallow pools of water (usually <1 m deep) intersected by embankment lands and lower, temporarily flooded areas. The proximity of the Mandra Lake and the Black Sea and seasonal climatic fluctuations create a wide variety of aquatic habitats spanning from fresh (<1‰) and brackish (1-10‰) to salt water (>10‰), including some hyperhaline waters during the summer (32-33 ‰, [43], Fig. 1).

The upper panel gives the location of the Poda Protected Areas in the vicinity of Bourgas, Bulgaria. Emergent lands are indicated in white, water is indicated in light grey. The lower panel shows the Poda Protected Area (dashed area). Emergent lands are indicated in white and water is indicated in light grey. Numbers designate salinity (‰) recorded for three ponds, two locations on the shore of the Black Sea, and one location at the mouth of the Mandra Lake. The two arrows show sites where tracks from snakes commuting between the land and the Black Sea were observed.

Field procedures

In April 2012, a total number of 19 snakes were captured by hand. Snakes were typically found while basking in the sun. Individuals were measured (snout-vent length [SVL] and total length [TL], ±0.5 cm), weighted (±1 g), and sexed by eversion of the hemipenis. Feeding and reproductive status were assessed by gentle palpation.

Only large adult females (>140 g, N = 13) were blood-sampled to avoid putative detrimental effects of the procedure on smaller individuals, and to avoid sex effects on plasmatic parameters. Blood (∼400 μl) was sampled through cardiocentesis using 30 G-needles. A small fraction (10 μl) of the blood was collected in a micro-capillary tube and centrifuged on site in a minihaematocrit Compur M1101 (Bayer) for 3 min to record haematocrit (packed blood cell volume, %). The remaining blood was centrifuged (3 min at 8,000 G) and the plasma was separated and stored at −25°C until assays were processed. Plasma sodium concentrations were assessed with an ISE module on a Pentra C 200 (Horiba Medical Ltd) compact chemistry analyzer.

At the end of the procedures (usually <30 min), snakes were released at the location of capture.

Water samples were collected from water bodies where N. tessellata were observed foraging and/or in the vicinity of which we collected snakes. These sampled stations included 3 ponds within Poda, 2 sites along the coast of the Black Sea as well as 1 site situated at the mouth of the Mandra Lake ( Fig. 1). Salinity (‰) was assessed with a Pocket Salt Meter (PAL-ES2, Atago).

Analyses

We quantified a body condition index (BCI) using residual scores from the linear regression between body size (SVL) and body mass (both variables were log transformed for linearity [44]). We excluded individuals with prey in the stomach from the BCI calculations.

Relationships between natremia and possible correlates (BCI, Hct) were investigated using Spearman rank correlations.

Results and Discussion

Free-ranging N. tessellata display highly variable plasma sodium concentrations (mean 169.9±13.2 mmol.l −1) ranging from normonatremia (which range from 130 to 160 mmol.l −1 in non-mammalian tetrapods [45]) to hypernatremia (up to 195.5 mmol.l −1, Fig. 2). Most individuals (N = 10, 77%) displayed hypernatremia, and only three snakes had values within the range of normonatremia (130-160 mmol.l −1 [45]). Classically, deviations of the osmotic balance trigger several behavioural and physiological adjustments in snakes. For instance, dehydrated and/or hypernatremic individuals tend to seclude themselves in well-buffered shelters in order to reduce additional water loss [8], [9]. Such behaviour is usually accompanied by a thermal depression and decreased metabolism which result in a strong reduction in activity levels [46], [47]. Apparently, the high natremia we recorded did not trigger such adjustments in N. tessellata. Indeed, all the individuals we captured were basking in the sun, or actively moving in the open, and tried actively to evade capture. Remnants of food were palpated in three individuals that did not display particularly low plasma sodium (155.6, 167.4 and 173.8 mmol.l −1 Na⁺ respectively). In addition, BCI was not related to plasma sodium (Spearman rank correlation, rs = −0.47, p>0.05), suggesting an absence of long-term effect of hypernatremia on foraging.

The dashed lines indicate the range of normonatremia (130-160 mmol.l −1 [45]) and the horizontal black line indicates mean normonatremia (145 mmol.l −1). For clarity, individuals are ranked by ascending order of natremia.

The elevated natremia we found in some individuals could be the result of mere dehydration (i.e., the more dehydrated an individual, the more concentrated its body fluids). However, this hypothesis seems unlikely as we did not find any relationship between plasma sodium and BCI (see above) or haematocrit (Spearman rank correlation, rs = 0.20, p>0.05), two parameters known to correlate with hydration state [17], [48]. Our results rather suggest that free-ranging N. tessellata gained salt during their day-to-day activities. Indeed, measurements of environmental salinity in Poda showed that most potential foraging areas were saline (up to 14.3‰, Fig. 1, see also [43]). Likely, Dice snakes foraged in water bodies that were brackish or saline, or indeed at sea (as witnessed by tracks of snakes commuting to the Black Sea, Fig. 1); and gained salt passively through permeable surfaces. Marine snakes display a significant reduction in salt gain and water loss through permeable surfaces [10]-[12], [49], and future studies should assess skin permeability to water and sodium in N. tessellata and compare coastal versus inland populations.

Voluntary or incidental (e.g., during prey capture) salt water drinking is an additional process that leads to salt gain [15]. Accordingly, marine forms usually display an increased ability to discriminate water salt content and to avoid salt water drinking [12], [16], [26], [50], [51]. We do not know whether N. tessellata is able to discriminate water salt content and/or to avoid salt water drinking and such issues need to be clarified. In addition to salt water drinking avoidance, many marine taxa can rely on behavioural osmoregulation such as fresh water drinking. Indeed, dehydrated and hypernatremic marine snakes are known to drink large amounts of fresh water when available to restore osmotic balance [9], [12], [16], [25]. Interestingly, two individuals (151.3 and 162.6 mmol.l −1 Na⁺ respectively) regurgitated copious amounts of fresh water upon capture, suggesting that these individuals have drank shortly before. The variety of aquatic habitats found in Poda (fresh, brackish and salt water, Fig 1) over a small spatial scale, may allow hypernatremic Dice snakes to easily access fresh water, and thus to periodically restore osmotic balance. Accordingly, specific environments characterized by low and/or variable salinity may have facilitated evolutionary transitions to marine life in snakes by allowing regular access to relatively fresh water over short time-scales and decreasing the cost of osmotic maintenance [13].

More generally, a review of plasmatic sodium concentration of snakes experimentally maintained in fresh water or seawater gives additional insights to our results ( Fig. 3 and references therein). These data suggest that when kept in fresh water, irrespective of their primary habitat (i.e., fresh- versus seawater) all species shared similar normonatremia (∼140-150 mmol.l −1, Fig. 3). Similarly, in full-strength seawater, plasma sodium increased in all species regardless from their osmoregulatory attributes (i.e., presence/absence of salt glands, Fig. 3, [25]). Importantly, survival differed among species and treatments, with strictly fresh water species ( Nerodia fasciata and N. sipedon) having decreased short-term (i.e., hours) survival in osmotically challenging treatments ( Fig. 3). Survival decreased also for salt tolerant species, although to a lesser extent, with only one species ( Thamnophis valida) out of three having its short-term survival decreased in full-strength seawater ( Fig. 3). The other salt tolerant species survived for several days in full-strength seawater. Survival stayed high (100%) in both groups of marine adapted snakes ( Fig. 3). Overall, these patterns seem to indicate that along a continuum of habitats use between fresh- and seawater, snake species display a concomitant physiological tolerance toward high plasma sodium, even in species lacking salt glands ( Figs. 2 and 3). In turn, this physiological flexibility would allow reducing detrimental effects of salt gain such as decreased activity levels and decreased short-term survival [26]. Such resistance would allow individuals to periodically access fresh water, and hence to occasionally restore their osmotic balance. Ultimately, in marine species having salt glands, such flexibility would allow excreting excess salt when natremia exceeds high thresholds [22], which would substantially decrease energetic costs linked to salt gland functioning [25].

These data were available from strictly fresh water species ( Nerodia fasciata and N. sipedon [24], [26]), salt tolerant species lacking salt glands ( N. clarckii clarckii, N. clarckii compressicauda, Thamnophis valida [24], [26]), amphibious sea kraits with functional salt glands ( Laticauda saintgironsi, L. laticaudata, L. semifasciata [24], [25]) and fully marine sea snakes with functional salt glands ( Acrochordus granulatus, Hydrophis elegans, H. cyanocinctus, Pelamis platurus [18], [19], [21]-[23]. The dashed lines indicate the range of normonatremia (130-160 mmol.l −1 [45]) and the horizontal black line indicates mean normonatremia (145 mmol.l −1). Numbers above the bars indicate survival rates (no number  = 100%). Data are mean values per species ± SD.

In conclusion, the combination of these data strongly suggest that the development of a physiological tolerance toward deviations of the osmotic balance (e.g., increased plasma sodium) might have been a critical innovation in the evolution of an euryhaline physiology and may well have preceded the evolution of salt glands. Although only few populations of N. tessellata are found in saline environments, our results show that these populations may be salt tolerant, and use saline water bodies despite lacking salt glands. In this respect, N. tessellata seems a promising study model (i.e., a marine snake prototype) of the secondary transition to marine life in vertebrates.

Acknowledgments

We thank Bruno Michaud for natremia assays and Leslie Babonis for sharing data on sea krait natremia. Andéaz Dupoué, Frédéric Angelier, Olivier Lourdais and an anonymous referee provided insightful comments on an earlier draft of the MS.

Author Contributions

Conceived and designed the experiments: FB YVK. Performed the experiments: FB YVK. Analyzed the data: FB YVK. Contributed reagents/materials/analysis tools: FB YVK. Wrote the paper: FB YVK.

References

1. 26. Dunson WA (1980) The relation of sodium and water balance to survival in sea water of estuarine and freshwater races of the snakes Nerodia fasciata, N. sipedon, and N. valida. Copeia 2: 268-280.

2. 28. Mebert K (Ed.) (2011) The Dice Snake, Natrix tessellata: Biology, Distribution and Conservation of a Palaearctic Species. Mertensiella 18, DGHT, Rheinbach, Germany.

3. 30. Gruschwitz M, Lenz S, Mebert K, Lanka V (1999) Natrix tessellata (Laurenti, 1768) - Würfelnatter. - In: Böhme W (Ed.): Handbuch der Amphibien und Reptilien Europas Band 3/II Schlangen (Serpentes) II:. - AULA-Verlag, Wiesbaden, Germany: 581-644.

4. 36. Ioannidis Y, Mebert K (2011) Habitat preferences of Natrix tessellata at Strofylia, northwestern Peloponnese, and comparison to syntopic N. natrix. Mertensiella 18: 302-310.

5. 51. Kidera N, Mori A, Tu MC (2013) Comparison of freshwater discrimination ability in three species of sea kraits (Laticauda semifasciata, L. laticaudata and L. colubrina). J Comp Physiol A 199: 191-195.

# data[].attributes.attachment_link.title
Hypernatremia in Dice Snakes (Natrix tessellata) from a Coastal Population: Implications for Osmoregulation in Marine Snake Prototypes

# data[].attributes.attachment_link.description
The widespread relationship between salt excreting structures (e.g., salt glands) and marine life strongly suggests that the ability to regulate salt balance has been crucial during the transition to marine life in tetrapods.

# data[].attributes.headline
Feeding behavior of the dice snake (Natrix tessellata) 

# data[].attributes.subject
Feeding behavior of the dice snake (Natrix tessellata) 

# data[].attributes.body
Using measurable behavioral components and corporal characteristics we recorded and analyzed the
feeding behavior of the piscivorous dice snake (Natrix tessellata).The analyzed parameters were: searching time,
searching speed, attack speed, prey handling time, ingestion time, body condition index (BCI) and fish body size
parameters. The correlation between these parameters and their effect on successful prey capture and consumption
was also examined. Searching time and searching speed was not affected by the other parameters of the snakes or
fish, however in case of repeated attacks the searching speed strongly correlated with the BCI. Attack speed was also
strongly influenced by the BCI. The successful outcome of an attack depends on the searching speed: a high
searching speed reduces the possibility of successful prey capture. Prey handling time is higher when fish is caught
by trunk and ingested either from head or from tail, in comparison with grasping on fish head or tail and starting
ingestion from the grasped body part. In two cases the fish caught by tail was ingested from head and in one case
caught by head and ingested from tail. In these exceptional cases the prey handling time also became high. The
ingestion time is independent of BCI but it is strongly affected by the weight and size of fish and also by the
direction of ingestion.

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Τhe possible effects of climate change on organisms-Theme 2

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Τhe possible effects of climate change on organisms-Theme 2

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The effect of climate change on organisms in Europe is a combination of all the previous first 4 options (1-4) but it is mainly driven by the second one.

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Fossil amphibians and reptiles from Plakias, Crete: A glimpse into the earliest late Miocene herpetofaunas of southeastern Europe

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Fossil amphibians and reptiles from Plakias, Crete: A glimpse into the earliest late Miocene herpetofaunas of southeastern Europe

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Fossil amphibians and reptiles from the earliest late Miocene (early Tortonian, MN 9) of Plakias (Crete, Greece) are described in this paper.

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Fossil amphibians and reptiles from Plakias, Crete: A glimpse into the earliest late Miocene herpetofaunas of southeastern Europe

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Fossil amphibians and reptiles from the earliest late Miocene (early Tortonian, MN 9) of Plakias (Crete, Greece) are described in this paper. Most of ...

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The Turkish gecko (scient. Hemidactylus turcicus) or Mediteranean house gecko is one of the most common reptiles in Crete, which is closely related to the Moorish gecko. Indeed, many people tend to confuse the two species that have similar characteristics but do not belong in the same species.

The house gecko has darker colors (in day) than Moorish gecko and reaches a total length of 10cm. At night the color its body colors turn to semi-translucent. Like Moorish gecko, it feeds on small arthropods and usually lurks on insects attracted to lights.

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Podarcis cretensis, endemic species, occupies shrubland, rocky areas and dry river beds.

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The artificial lake of Agia is located 9 km from Chania and receives the White Mountains water through many underground springs.
Hosts the largest variety of aquatic plants in Crete, but also very important species of fauna such as rare species of frogs. Also, many migratory birds find shelter there. Nowadays, there are problems in the area like the irrigation and the introduction of the American bullfrogs,  wiping out the endemic frog of Crete, Pelophylax cretensis.