Article

Effect of Salinity on the Survival, Ions and Urea Modulation in Red-eared Slider(Trachemys scripta elegans)

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Abstract

To understand the tolerance to salinity and osmoregulation of the introduced Trachemys scripta elegans, the salinity stress of four groups (salinity 5‰, 15‰, 25‰ and control group) were conducted. Inorganic ions, osmotic pressure, glucose and aldosterone of blood and urine in T. s. elegans (BW: 125.60 ± 19.84 g) were analyzed at 30 d, 60 d and 90 d stress. The results showed that: 1) inorganic ions concentration of blood and urine increased with ambient salinity, which indicated that high influx of ions was combined with higher outflow when exposed to saline water in T. s. elegans. However, blood aldosterone decreased with increasing salinity, which indicated that an increased sodium intake resulting in a diminished aldosterone production. However, with elapsed time, inorganic ions in urine decreased, which indicated that inorganic ions in blood would be accumulated, and Na+ and Clin the plasma inevitably build up to harmful levels, at last death was happening when T. s. elegans was exposed to salinity 25 during 90 d salinity stress; 2) blood osmotic pressure increased as ambient salinity increased, it would reach 400 mOsm/kg in the group of salinity 25, which was about 1.5 fold of the control group. Higher blood osmotic pressure was due to both higher blood ions and urea concentrations. There may be another mechanism to avoid an excess of NaCl together with an important loss of water using one of the end-products of nitrogen metabolism; 3) blood glucose in each group except the group of salinity 5 decreased with time elapsed and with salinity increased. Therefore, we can conclude that T. s. elegans is an osmoregulator that limits the entry of Na+ and Cl-, but can also tolerate certain degrees of increases in plasma Na+ and Cl-. When ambient salinity was lower than 15‰, T. s. elegans can increase blood osmotic pressure by balancing the entry of NaCl with the secretion of aldosterone decreased, and by accumulating blood urea for osmoregulation effectors, and survive for at least three months. These results could provide theoretical basis for salinity tolerance and the invasion on physiological mechanism for T. s. elegans.

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... When subjected to ambient salinity change, T. s. elegans increased serum glucose levels, and the activities of creatine kinase (CK), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), and alkaline phosphatase (ALP) in liver (Shu et al., 2012). Our previous studies have shown that T. s. elegans can increase blood osmotic pressure by balancing the entry of sodium and chloride ions with a decrease in the secretion of aldosterone, and by accumulating plasma urea for osmoregulation when ambient salinity was lower than 15 (Hong et al., 2014). However the molecular basis of these adaptive responses has not been studied in T. s. elegans. ...
... As a normally freshwater species, the red-eared slider T. s. elegans, does not possess salt glands, and requires osmoregulation to survive when entering environments of higher salinity (e.g., brackish or estuarine water). The physiological research has shown that T. s. elegans can increase blood osmotic pressure by balancing the entry of NaCl with the decreased secretion of aldosterone, and accumulating urea and free amino acids in blood (Hong et al., 2014). In our study, many DEGs were classified into some dominant categories including the macromolecule metabolic process, ion transport and ion transmembrane et al., 2009;Rider et al., 2006). ...
... Genes associated with transporting molecules related to metabolic processes were also modulated in association with an up-regulation of genes involved in ATP energy production. As salinity level increases, acclimation of T. s. elegans to elevated salinity conditions requires investment of energy to maintain their homeostatic balance (Hong et al., 2014). In our study, the DEGs related to energy production and conversion including ATP6, COX1, COXIII, CYTb, and CYP17A1 increased with ambient salinity increased, which suggested that a requirement for more energy by T. s. elegans during raised salinity conditions. ...
Article
The red-eared slider (Trachemys scripta elegans), identified as one of the 100 most invasive species in the world, is a freshwater turtle originally from the eastern United States and northeastern Mexico. Field investigations have shown that T. s. elegans can survive and lay eggs in saline habitats. In order to understand the molecular mechanisms of salinity adaptation, high-throughput RNA-Seq was utilized to identify the changes in gene expression profiles in the liver of T. s. elegans in response to elevated salinity. We exposed individuals to 0, 5, or 15 psu (practical salinity units) for 30 days. A total of 157.21 million reads were obtained and assembled into 205138 unigenes with an average length of 620 bp and N50 of 964 bp. Of these, 1019 DEGs (differentially expressed genes) were found in the comparison of 0 vs. 5 psu, 1194 DEGs in 0 vs. 15 psu and 1180 DEGs in 5 vs. 15 psu, which are mainly related to macromolecule metabolic process, ion transport, oxidoreductase activity and generation of precursor metabolites and energy by GO (Gene Ontology) enrichment analyses. T. s. elegans can adapt itself into salinity by balancing the entry of sodium and chloride ions via the up-regulation expression genes of ion transport (potassium voltage-gated channel subfamily H member 5, KCNH5; erine/threonine-protein kinase 32, STK32; salt-inducible kinase 1, SIK1; adiponectin, ACDC), and by accumulating plasma urea and free amino acid via the up-regulation expression genes of amino acid metabolism (ornithine decarboxylase antizyme 3, OAZ3; glutamine synthetase, GLUL; asparaginase-like protein 1b, ASRGL; L-amino-acid oxidase-like, LAAO; sodium-dependent neutral amino acid transporter B, SLC6A15s; amino acid permease, SLC7A9) in response to osmotic regulation. An investment of energy to maintain their homeostatic balance is required to salinity adaptation, therefore, the genes related to energy production and conversion (F-ATPase protein 6, ATP6; cytochrome c oxidase subunit I, COX1; cytochrome c oxidase subunit III, COX3; cytochrome b, CYTb; cytochrome P450 17A1, CYP17A1) were up-regulated with the increase of gene expression associated with lipid metabolism (apolipoprotein E precursor, APoE; coenzyme Q-binding protein, CoQ10; high-density lipoprotein particle, SAA) and carbohydrate metabolism (HK, MIP). These findings improve our understanding of the underlying molecular mechanisms involved in salinity adaptation and provide general guidance to illuminate the invasion potential of T. s. elegans into saline environments.
... The increase of plasma osmolality with salinity has also been reported in different other freshwater species (e.g. Gilles-Baillien 1970;Seidel 1975;Hong et al. 2014). ...
... In contrast to plasma, and except in Trachemys scripta elegans (Hong et al. 2014), there are no data on urine chloride concentration in other studied freshwater turtle species. In M. l. saharica, the percentages of excreted chloride in urine were 30 and 72%, respectively in freshwater and brackish/salt waters. ...
... In brackish/saline waters, the corresponding values were at the upper limit of the range in other species (4.5 mM). As for the urine, potassium concentrations in M. l. saharica kept in brackish/saline waters were lower than those for other species (Gilles-Baillien 1970;Hong et al. 2014); this might be because of the fact that this mono-cation, just like sodium, can also usually be adsorbed onto urates. ...
Article
The marginal populations of the Sahara blue-eyed pond turtle, Mauremys leprosa saharica, in the southern-most species distribution range in the pre-Saharan areas of north-west Africa, are faced with extreme environmental conditions of arid climate and anthropogenic and climate change mediated water and land salinisation. In the current study, we investigated a small and isolated population of M. l. saharica at Sidi El Mehdaoui oasis in the Lower Draa River, southern Morocco, in order to assess its osmo- and iono-regulatory abilities and tolerance to salinity and dehydration. Upon capture, turtles were weighed and measured for shell dimensions and blood and voided urine were taken. Tests of exposure to different levels of water salinity (0%, 35%, and 50% seawater) and maintenance out of water (estivation simulation) were carried out. Osmolalities and Na⁺, Cl⁻, K⁺, and urea concentrations were determined in plasma and voided urine, and glycaemia was measured in blood, before and after tests. Turtles were able to survive in brackish waters with a salinity as high as 24% seawater (8.4 ppt). Their voided urine was hypotonic to plasma, which indicated that they could use their bladder water reserves for osmo- and iono-regulation until the iso-osmocity level beyond which osmotic and ionic anhomeostasy can occur. Experimental tests showed that the osmo- and iono-regulatory capacities of these turtles are relatively limited, and not enough effective to allow them to survive for long-term periods in brackish/saline waters or out of water, because of dehydration indicated by progressive weight loss to a critical threshold. The increased drought, water salinisation and habitat fragmentation related to anthropogenic activities and climate change, represent great threats that can create habitats exceeding the species’ threshold for a long-term persistence of the vulnerable small marginal populations of the Saharan pond turtle. So, conservation measures of these populations and their habitats are urgently needed.
... While these mechanisms are effective means for tolerating saline waters for a few freshwater turtle species (Bower et al., 2016;Dunson and Dunson, 1975), they are often ineffective for many others that are highly sensitive to salinities >10 ppt (Agha et al., 2018). Further, in previous studies where turtles were chronically exposed to increased salinity (17.5-35 ppt), rapid body water loss occurred, which resulted in increased plasma osmolality and electrolytes, decreased muscle moisture, body mass loss and, in some cases, mortality after 7 days of salinity exposure (Bentley et al., 1967;Bower et al., 2016;Dunson and Seidel, 1986;Dunson, 1979;Hong et al., 2014). Because these results have been found for a limited number of species, further investigation of how freshwater turtles respond to acute and chronic salinity stress is important for conservation planning, as over 90% of coastal freshwater turtles around the world will likely be affected by sea-level rise and resulting salinity by 2100 (Agha et al., 2018). ...
... All hoop traps were ∼1.8 m long, 63.5-cm hoop diameter with 3.8 cm squared mesh, made with knotted nylon netting tied to three galvanized steel hoops (Memphis Net and Twine, Memphis, TN). We determined our sample size based on variation in blood chemistry from other salinity tolerance studies on freshwater turtles (Bower et al., 2016;Hong et al., 2014). We individually marked captured turtles by creating notches in 1-3 marginal scutes on their carapace. ...
... tanks to ensure balanced sample size and distributions of sex and populations among treatments (Table 2). We selected these experimental treatments based on the upper tolerance specified for other freshwater turtle species (Bower et al., 2016;Dunson and Mazzotti, 1989;Hong et al., 2014) and maximum water salinities (∼12 ppt) in areas where Western Pond Turtles have been observed and/or captured in Suisun Marsh (Bay-Delta Live, 2018). This salinity gradient also best represented the range of salinities that these turtles may potentially be exposed to in the near future in inland parts of their range (Palaima, 2012;Agha et al., 2018). ...
Article
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Sea-level rise, drought and water diversion can all lead to rapid salinization of freshwater habitats, especially in coastal areas. Increased water salinities can in turn alter the geographic distribution and ecology of freshwater species including turtles. The physiological consequences of salinization for freshwater turtles, however, are poorly known. Here, we compared the osmoregulatory response of two geographically separate populations of the freshwater Western Pond Turtle (Actinemys marmorata)—a species declining across its range in western North America—to three constant salinities: 0.4 ppt, 10 ppt and 15 ppt over 2 weeks. We found that turtles from a coastal estuarine marsh population regulated their plasma osmolality at lower levels than their conspecifics from an inland freshwater creek population 45 km away. Plasma osmolalities were consistently lower in estuarine marsh turtles than the freshwater creek turtles over the entire 2-week exposure to 10 ppt and 15 ppt water. Furthermore, estuarine marsh turtles maintained plasma osmolalities within 1 SD of their mean field osmolalities over the 2-week exposure, whereas freshwater creek turtles exceeded their field values within the first few days after exposure to elevated salinities. However, individuals from both populations exhibited body mass loss in 15 ppt water, with significantly greater loss in estuarine turtles. We speculate that the greater ability to osmoregulate by the estuarine marsh turtles may be explained by their reduced feeding and drinking in elevated salinities that was not exhibited by the freshwater creek population. However, due to mass loss in both populations, physiological and behavioural responses exhibited by estuarine marsh turtles may only be effective adaptations for short-term exposures to elevated salinities, such as those from tides and when traversing saline habitats, and are unlikely to be effective for long-term exposure to elevated salinity as is expected under sea-level rise.
... However, the energetic cost of osmoregulation is higher in hypersaline treatment, in which the ion concentrations of blood and water are disparate, potentially making less energy available for growth. Therefore, when the turtles are subjected to stress from salinity, the blood glucose quickly increases, as reported by Shu et al. [31] and Hong et al. [32]. ...
... BUN significantly increased with water salinity. This result is in agreement with data on redeared slider reared at 5, 15, and 25 ppt [32]. Possible reasons might include increased urea retention in urinary bladder [40] or increased rate of urea synthesis [41]. ...
Article
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Northern river terrapins (Batagur baska Gray, 1831) are Asia’s largest turtles living in both freshwater and brackish water. In the current study, the optimal salinity for head-starting programs of this critically endangered species was investigated in order to serve the well-being of turtles before release to natural habitat. Forty-eight terrapins (54.64 ± 0.18 g initial body weight) were randomly distributed to four salinity levels (0, 4, 8, and 12 ppt) and reared for eight weeks, using three replicates with four terrapins each. At the end of rearing trial, growth performance and feed utilization parameters were superior in terrapins reared at 4 ppt, followed by 8 ppt in the rank order of treatments. Negative stress responses were observed in terrapins reared at 12 ppt, as the fecal activity of amylase-to-trypsin ratio was changed significantly, but not that of proteolytic enzymes. The fecal thermal transition properties indicated an abundance of nutrients in the post-absorptive phase for terrapins reared at 4 ppt, followed by the 8 ppt treatment group. The preferred 4 ppt salinity had no negative effects on the health status of the terrapins in terms of carapace elemental composition or hematological parameters. Second-order polynomial regression suggests 4.35 ppt as the optimal salinity for maximal weight gain. Findings from the current study could be directly used in ex situ conservation programs of northern river terrapins before release to natural habitat.
... For example, mean conductivity levels increased from ~ 9900 to ~ 10,094 μS/cm near Red Bluff Dam and from ~ 8000 to ~ 20,467 μS/cm approximately 152 river km downstream from Red Bluff Dam. Freshwater organisms are typically not adapted to such high salinity levels, and high concentrations of salts can be toxic 8,39 . Studies have shown that excess salinity can alter food webs in freshwater systems 8,40 , and can trigger trophic cascades in ecological communities 40 . ...
Article
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The lower Pecos River located in the southwest USA, is a naturally saline river system that has been significantly altered in relatively recent years. Climate change, coupled with anthropogenic disturbances such as dam construction have led to portions of the river becoming more susceptible to increased salinization and declines in water quality. These alterations have been documented to be detrimental to multiple freshwater communities; however, there is a lack of knowledge on how these alterations influence long-lived species in the river, such as freshwater turtles, where the effects can appear over dramatically different temporal scales. The Rio Grande Cooter (Pseudemys gorzugi) is a species of concern known to occur in the Pecos River. To understand the current distribution and habitat requirements for P. gorzugi in the Pecos River, we used a single-season, single-species occupancy modeling framework to estimate occurrence while accounting for the sampling process. Day of year, water surface area, and water visibility had the greatest influence on the ability to detect the species given a sampling unit is occupied. Conductivity (a measure of salinity) had the greatest influence on the occupancy probability for the species, where sites with higher conductivity coincided with lower occupancy probabilities. This study indicates that increased salinization on the lower Pecos River is a cause for concern regarding freshwater turtle populations within the Chihuahuan Desert.
... Regarding salinity, both species appear to tolerate a certain degree of salinity: M. leprosa has been recorded in brackish estuarine waters in Portugal [137] and in coastal brackish lagoons along the Mediterranean coast of the Iberian Peninsula [102]. T. s. elegans has been found in brackish lagoons (<10 ppm) in South Carolina, USA [138], and in environments with salinities ranging between 0.1‰ and 26‰ in China [139]. In agreement with these results, we did not find strong differences in the environmental preferences of both species. ...
Article
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The global degradation of wetlands is increasing their susceptibility to invasions, which is greatly determined by a niche overlap between native and invasive species. We analyze its role in regulating the coexistence of the native Mediterranean stripe-necked terrapin Mauremys leprosa and the invasive Red-eared Slider Trachemys scripta elegans in a coastal wetland. We analyzed both water chemistry and landscape attributes, using variance-partitioning analysis to isolate the variance explained by each set of variables. Then, the influence of environmental variables on species co-occurrence patterns was assessed by using latent variable models (LVM), which account for correlation between species that may be attributable to biotic interactions or missing environmental covariates. The species showed a very low niche overlap, with clear differences in their response to environmental and landscape filters. The distribution of T. s. elegans was largely explained by landscape variables, preferring uniform landscapes within the daily movement buffer, whereas at larger scales, it was associated with a high diversity of habitats of small and uniform relative sizes. A high percentage of the distribution of M. leprosa was unexplained by the measured variables and may be related to the competitive exclusion processes with T. s. elegans. The species was positively related with large patches with high perimeter values or ecotone area at medium spatial scales, and it was benefited from a marked heterogeneity in the patches’ size at larger scale. According to latent variable models, both species had wide eutrophication and salinity tolerance ranges, but they showed different environmental preferences. T. s. elegans was related to eutrophic freshwater environments, whereas M. leprosa was related to more saline and less eutrophic waters. Our results suggest that M. leprosa modifies its habitat use in order to avoid interaction with the T. s. elegans. Thus, management actions aimed at removing the invasive species from the territory and promoting habitat heterogeneity might be needed to protect M. leprosa and avoid local extinctions.
... Our previous studies have shown that T. s. elegans can survive for more than 3 months in saline environments (<15‰; Hong et al., 2014) or promote the antioxidant defense system against the oxidative stress induced by salinity (Ding et al., 2019) and that during this time, they increase their plasma triglyceride and glucose levels, probably supporting increased fuel/energy needs for survival in the saline environment (Shu et al., 2012). Transcriptomic analyses of T. s. elegans exposed to saline environments have shown that lipid metabolism pathways are differentially regulated, relative to controls in freshwater, suggesting a strong link between lipid metabolism and salinity-tolerance (Hong et al., 2018). ...
Article
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Aquatic animals have developed various mechanisms to live in either hyperionic or hypoionic environments, and, as such, not many species are capable of surviving in both. The red-eared slider turtle, Trachemys scripta elegans, a well-known freshwater species, has recently been found to invade and inhabit brackish water. Herein, we focus on some of the metabolic adaptations that are required to survive and cope with salinity stress. The regulation of the adenosine monophosphate (AMP)-activated protein kinase (AMPK), a main cellular “energy sensor,” and its influence on lipid metabolism were evaluated with a comparison of three groups of turtles: controls in freshwater, and turtles held in water of either 5‰ salinity (S5) or 15‰ salinity (S15) with sampling at 6, 24, and 48 h and 30 days of exposure. When subjected to elevated salinities of 5 or 15‰, AMPK mRNA levels and AMPK enzyme activity increased strongly. In addition, the high expression of the peroxisome proliferator activated receptor-α (PPARα) transcription factor that, in turn, facilitated upregulation of target genes including carnitine palmitoyltransferase (CPT) and acyl-CoA oxidase (ACO). Furthermore, the expression of transcription factors involved in lipid synthesis such as the carbohydrate-responsive element-binding protein (ChREBP) and sterol regulatory element-binding protein 1c (SREBP-1c) was inhibited, and two of their target genes, acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS), were significantly decreased. Moreover, exposure to saline environments also increased plasma triglyceride (TG) content. Interestingly, the content of low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) in plasma was markedly higher than the control in the S15 group after 30 days, which indicated that lipid metabolism was disrupted by chronic exposure to high salinity. These findings demonstrate that activation of AMPK might regulate lipid metabolism in response to salinity stress through the inhibition of lipid synthesis and promotion of lipid oxidation in the liver of T. s. elegans. This may be an important component of the observed salinity tolerance of these turtles that allow for invasion of brackish waters.
... Differences in urea sensitivity were also noted between control and anoxic conditions for both liver and red muscle PK (Tables 3 and 4). Urea has been noted in previous studies as important in the osmoregulation of turtles during periods of dehydration and for tolerating increased salinity (Uchiyama et al., 2009;Hong et al., 2014). However, T. s. elegans undergoes anoxia at the bottom of lakes and is not faced with dehydration stress, so urea accumulation is negligible on a physiological level. ...
Article
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Background Pyruvate kinase (PK) is responsible for the final reaction in glycolysis. As PK is a glycolytic control point, the analysis of PK posttranslational modifications (PTM) and kinetic changes reveals a key piece of the reorganization of energy metabolism in an anoxia tolerant vertebrate. Methods To explore PK regulation, the enzyme was isolated from red skeletal muscle and liver of aerobic and 20-hr anoxia-exposed red eared-slider turtles ( Trachemys scripta elegans ). Kinetic analysis and immunoblotting were used to assess enzyme function and the corresponding covalent modifications to the enzymes structure during anoxia. Results Both muscle and liver isoforms showed decreased affinity for phosphoenolpyruvate substrate during anoxia, and muscle PK also had a lower affinity for ADP. I50 values for the inhibitors ATP and lactate were lower for PK from both tissues after anoxic exposure while I50 L-alanine was only reduced in the liver. Both isozymes showed significant increases in threonine phosphorylation (by 42% in muscle and 60% in liver) and lysine methylation (by 43% in muscle and 70% in liver) during anoxia which have been linked to suppression of PK activity in other organisms. Liver PK also showed a 26% decrease in tyrosine phosphorylation under anoxia. Discussion Anoxia responsive changes in turtle muscle and liver PK coordinate with an overall reduced activity state. This reduced affinity for the forward glycolytic reaction is likely a key component of the overall metabolic rate depression that supports long term survival in anoxia tolerant turtles. The coinciding methyl- and phospho- PTM alterations present the mechanism for tissue specific enzyme modification during anoxia.
... 1980198019801993;1994;Shu et al. 2012Hong et al. 2014 Clark & Gibbons 1969;Hart 1983 Mann-Whitney U test ...
Article
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... Tot i que les variables ambientals no siguin determinants per a la distribució de l'espècie al Delta, els resultats obtinguts indicarien que aquesta prefereix ambients amb baixa salinitat i amb nivells elevats d'eutrofització, una tipologia d'ambient d'elevada productivitat idoni per a espècies de tortugues aquàtiques continentals considerades generalistes (Lindeman, 1996;Souza and Abe, 2000). Aquestes preferències mostrades per l'espècie al Delta del Llobregat serien molt similars a les descrites en altres zones d'introducció (Ferronato et al., 2009;Hong et al., 2014;Souza and Abe, 2000) i a la seva distribució nativa . La població estudiada de T. s. elegans del Delta del Llobregat representa aproximadament el 40% dels registres de tortugues aquàtiques continentals a la zona. ...
Thesis
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... As well as increases in Na ? , Mg 2? and Ca 2? values in red-eared slider, Trachemys scripta elegans (Hong et al. 2014), and increase in Na ? , K ? ...
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The aim of this study was to assess the effects of vitamin C (vitC) on the growth, skeletal abnormalities (vertebral column and lack of operculum), blood biochemical parameters, haematocrit, survival and resistance to salinity stress in common carp fry (0.5 ± 0.08 g). Fish were fed diets containing vitC at different levels: 0 (control), 50, 100 and 1000 mg kg−1 diet for 48 days. The results showed that there was a significant increase in final weight, weight gain and specific growth rate in those fish fed vitC diets compared with the control (P < 0.05). Food conversion rate of fish fed vitC diets was significantly (P < 0.05) lower than the control group. On the other hand, abnormalities in the operculum and vertebral column were found in fish fed the vitC-free diet, but did not significantly different compared with treatment groups (P < 0.05). Challenges were carried out after 48 days of feeding, to determine the effect of vitamin C on resistance to different salinities (0, 6 and 12 ppt). Cortisol, haematocrit (fish fed control diet), sodium, potassium, calcium and magnesium levels increased with the increase in salinity (P < 0.05). Haematocrit levels of fish fed the vitamin C-supplemented diets were not significantly affected by different salinities (P > 0.05). In addition, supplementation of vitC significantly increased survival rate and resistance to salinity stress challenge of fed fish. These results confirm that vitC improves growth performance, skeletal development, blood parameters, survival and resistance to salinity stress of common carp fry, a very important fish species in the Caspian Sea.
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To explore the adaptation mechanism of Hainan medaka, Oryzias curvinotus, to salinity, this study performed a histological and RNA‐Seq comparative analysis of female medaka liver with different salinities (0, 15 and 30 practical salinity unit [psu]). In the 30 psu group, the volume of hepatocytes was increased and cytoplasmic fat accumulated. A total of 83,758 unigenes were assembled by RNA‐Seq, of which 31,147 were annotated. In total, 922 differentially expressed genes (DEGs) were obtained, and the detection results of 24 DEGs by quantitative polymerase chain reaction (qPCR) were consistent with the RNA‐Seq data. Gene ontology (GO) enrichment showed that DEGs were mainly involved in biological processes, such as substance synthesis and transport, energy metabolism, signal transduction, and had catalytic activity and binding functions. Kyoto Encyclopedia of Genes and Genomes enrichment analysis showed that DEGs were significantly enriched in steroid biosynthesis, glycerophospholipid metabolism, peroxisome proliferator‐activated receptor signaling pathway, and insulin signaling pathway that regulate lipid metabolism. The results of this study highlight the response of the liver transcriptome to long‐term environmental salinity changes and provide a basis for the application of the medaka genetic resources.
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Environmental enrichment supports the well-being and welfare of captive animals. In the current study, the most suitable form of enrichment device for captive green turtles (Chelonia mydas) was investigated, to support head-start programs rearing turtles for release into their natural habitat. Fifteen-day-old turtles (113-114 g initial weight, n = 75) were randomly distributed into 15 experimental plastic tanks, comprising 5 treatments across three pools of each condition. The turtles in the experimental groups were exposed to four forms of enrichment devices (RS, ring shape; HSQS, hollow square shape; SS, sphere shape; CS, cylinder shape), and their outcomes related to growth, feed utilization, behavior, reduction of injury from conspecifics, and several health parameters were compared to those of a control group. At the end of the 10-week trial, the growth and feed utilization parameters did not differ across the five groups (p > .05). Of the turtles in the experimental treatments, those in the RS treatment spent more time interacting with the enrichment device, followed by the HSQS group. The percentage of wounds suffered through biting was significantly reduced in the groups exposed to enrichment devices, notably in the turtles exposed to the SS device, followed by the RS device. Significant differences between experimental groups in the specific activities of the major intestinal protein-digesting enzymes (trypsin and chymotrypsin) were observed. There were no effects noted in the hematological parameters and the main carapace elemental profile as compared to the control treatment. These findings suggest that the RS device is most appropriate in enriching the environment of juvenile green turtles in captivity programs, as well as in zoos or aquaria.
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Globally, the increase in sea levels is leading to salinization of freshwater, which might influence the freshwater organisms such as red-eared slider, Trachemys scripta elegans. The turtle can invade brackish water environments, in which it must deal with elevated salinity in the gastrointestinal tract that could impact the intestinal function. The intestinal barrier provides a front-line of organismal defense against the chemical and biological environmental insults. In this study, the adaptive functions of the intestinal barrier including intestinal histomorphology, genes involved in intestinal barrier functions, and the intestinal micro-ecosystem were analyzed in the turtles exposed to freshwater (S0), 5‰ salinity (S5) and 15‰ salinity (S15) water for 30 days. The results showed that the intestine of T. s. elegans maintained normal histomorphological structure in the S5 group, whereas the villus height, crypt depth and the number of goblet cells in the S15 group were lower than that in the S5 and S0 groups. In addition, the relative expression levels of epithelial tight junction-related genes and intestinal immune-related genes in the gut were significantly upregulated in the S15 group, compared to the freshwater group. Mucin-2 gene expression was downregulated, but mucin-1 transcript levels were upregulated in salinity-treated groups. Furthermore, the abundances of phylum Proteobacteria, and genera Morganella and Aeromonas in the intestine were particularly enhanced in the S15 group than the S0 and S5 groups. Taken together, these results indicate that the intestinal barrier plays a protective role in T. s. elegans adaptation to brackish water environments. Our results provide a perspective on the evolution of salinity tolerance and help to evaluate the potential danger of the turtle to other species, and understand the challenges that other species must meet with rising sea levels.
Article
The freshwater red-eared slider (Trachemys scripta elegans) is found not only in freshwater but also in coastal saline habitats. Hyperosmotic salinity can induce cell damage. p53, regarded as the guardian of the genome, is very important and versatile in response to the change of environment. In this study, the role of p53 in T. s. elegans under environmental salinity change will be explored. The results indicated that amino acid sequence of p53 showed high similarity to p53 of other species. In addition, the expression of p53 showed differences in various tissues under normal condition. Under salinity stress, the mRNA levels of p53 in the liver increased significantly at 48 h with 15‰ group (15 practical salinity units-exposed group). In the heart, p53 mRNA levels increased at 6 h in 5‰ (5 practical salinity units) and 15‰ groups. Furthermore, the changes of p21 mRNA expression levels in liver and heart were similar to p53, while cyclin D1, cyclin-dependent kinase4 (CDK4) and cyclin-dependent kinase6 (CDK6) showed opposite changes to p53. Moreover, Bax and caspase 3 mRNA expression levels were similar to p53, respectively, while Bcl-2 showed opposite changes. The positive cells of apoptosis were found in the liver of 15‰ at 48 h and 30 d of chronic stress. Taken together, these results indicated that the T. s. elegans may protect itself by regulating cell cycle progression and apoptosis of damaged cells under salinity stress, which played an important role for T. s. elegans in salinity adaptation.
Article
The red-eared slider (Trachemys scripta elegans), a freshwater turtle, is an invasive species in many parts of the world where it survives in both freshwater and coastal saline habitats. High salinity can induce reactive oxygen species (ROS) production and lead to oxidative damage. In this study, we investigate the antioxidant defense mechanisms of T. s. elegans in response to salinity stress. The results showed that the mRNA expression levels of superoxide dismutase (SODs), catalase (CAT) and glutathione peroxidase (GSH-PXs) were significantly increased in both 5 psu and 15 psu groups at the early stages of salinity exposure (generally 6–48 h), but typically returned to control levels after the longest 30 d exposure. In addition, hepatic and cardiac mRNA levels of the NF-E2-related factor 2 (Nrf2), showed a similar upregulation as an early response to stress, but decreased at 30 d in the 5 psu and 15 psu groups. The mRNA levels of the negative regulator of Nrf2, kelch-like ECH associating protein 1 (Keap1), exhibited the opposite pattern. Moreover, mRNA expression levels of target of rapamycin (TOR) and ribosomal protein S6 kinase 1 (S6K1) in liver and heart showed roughly similar patterns to those for Nrf2. Furthermore, the content of malondialdehyde (MDA) was significantly increased in liver, especially in the 15 psu group by ~2.5-fold. Taken together, these results indicate that T. s. elegans may activate the TOR-Nrf2 pathway to modulate antioxidant genes transcription in order to promote enhanced antioxidant defense in response to salinity stress.
Chapter
The red-eared slider (Trachemys scripta elegans) is listed as one of the 100 worst invasive species in the world. At present, it is widely distributed in aquatic habitats in China. In order to collect detailed ecological data in invaded regions, to clarify the invasive status, ecological impacts and adaptative mechanisms, and to provide data for legislation and management, we conducted a series of studies on the invasion ecology of the exotic red-eared slider from 2008 to 2014 in China. The results showed that this slider species has a high ecological tolerance and behavioral plasticity, which result in a strong competitive ability and a large preponderance in local communities. The slider poses a big threat to native biodiversity and ecosystems in China. All our results suggest that we should enact laws to ban the import of sliders and to make a scientific management of turtle farms, pet markets, and animal release. In addition, the propaganda and public education should be regularly done to enhance the knowledge and public awareness of negative effects of biological invasions.
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Plasma aldosterone concentrations have been measured by radioimmunoassay in two lizard species,Uromastix acanthinurus andTiliqua rugosa, and control levels were 36.044.73 ng/100 ml and 31.745.60 ng/100 ml respectively, which fall within the range reported for this hormone in mammals. Chronic salt loading for a period of 7 days depressed aldosterone levels in both species but chronic water loading produced a significant elevation only in the case ofUromastix acanthinurus. Plasma aldosterone and sodium concentrations were significantly correlated inUromastix (r=0.77) but the correlation was doubtful in the case ofTiliqua (r=0.41). Dexamethasone blockade for a period of 4 days depressed aldosterone levels inTiliqua rugosa but synthetic ACTH at a dosage of 2 I.U./100 g did not increase aldosterone concentrations in either species, although plasma corticosterone concentrations were elevated by the treatment. The extent to which aldosterone may be implicated in the regulation of sodium metabolism in reptiles and its possible action on extra-renal routes of electrolyte excretion is discussed.
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The aim of the present study was to investigate the effects of different salinities (0‰, 6‰ and 12‰) and temperatures (23, 27 and 31 °C) on the food consumption, growth, blood biochemistry and haematocrit of Goldfish. After 45 days of exposure to different salinities and temperatures, Goldfish showed a good adaptation to these salinities and temperatures in terms of blood biochemistry (glucose and triglyceride) and haematocrit. Salinities (0‰ and 6‰) and temperatures (23 and 27 °C) did not affect the weight gain, specific growth rate, final biomass and feed conversion rates, but these parameters were significant (PPCarassius auratus, a freshwater stenohaline fish, showed good growth in saline waters with maximum 12‰ salinity and 31 °C temperature.
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Slider turtles, Chrysemys scripta, attain biologically and statistically significantly larger sizes on Atlantic Coast islands than do natural populations on the mainland. The sizes of individuals on these islands are comparable to those reported previously for turtles from a unique aquatic situation in a thermally altered reservoir. Higher quality diets and warmer temperatures appear to be satisfactory explanations for the island and reservoir situations.
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Large numbers of red-eared sliders (Trachemys scripta elegans) have been imported into Europe for several years as part of the pet trade. These alien turtles have entered habitats where they interact with native pond turtles (Emys orbicularis). We investigated competition for basking sites, because optimal basking sites may be a restricted resource in the wild. We used experimental ponds to compare basking-place selection between single-species groups and mixed-species groups. Both species preferred basking places in open deep water. In mixed groups the sliders outcompeted the European turtles for preferred basking places. Although competition for basking places is only one component of resource partitioning between these two species, it provided an insight into the relationships between an introduced and a native species. Behavioural asymmetries like those detected in our experiments argue for the caution principle in the animal trade.
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Recent massive imports of slider turtles, (Trachemys scripta elegans) into Europe as pets have induced frequent release of these exotic turtles in natural habitats. As a consequence, T. s. elegans is now widely distributed in most wetlands. Moreover, reproduction of this species has been repeatedly observed in Europe under Mediterranean climatic conditions. In this context, we studied competition between this introduced species and the European pond turtle (Emys orbicularis) under experimental conditions. We compared weight variation and survival between control groups and mixed groups during three years of monitoring. We found both weight loss and high mortality in E. orbicularis of the mixed groups. This study argues for applying a precaution principle and stopping slider turtle introductions in all wetlands in Europe.
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When held in air for up to 24 h, crayfish accumulated Ca(2+) and Mg(2+) in their haemolymph in direct proportion to raised levels of lactate. K(+) levels were highly variable, with elevated levels associated with morbidity. Lactate accumulation in the haemolymph was reflected in proportional increases in lactate levels in the carapace and muscle. Pieces of carapace incubated in saline containing elevated levels of lactate accumulated lactate to up to half the dissolved concentration. Measured levels in the carapace, relative to its water content, implied that lactate accumulated in the carapace in a combined form, possibly complexed to calcium. The exoskeleton seems to provide a reserve of buffering capacity and a sink for lactate during anaerobic metabolism. A similar mechanism has been identified in pond turtles.
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Sea turtles can regulate levels of the majority of the solutes (the monovalent ions) in their body fluids via the secretions of the post-orbital salt glands. The concentration of these secretions can be twice that of sea water. In some cases, the osmotic concentration of the urine may be greater than that of the plasma but this concentration is probably more important for waste removal than for osmoregulation. An examination of the salt and water regulation of sea turtles provides an opportunity to consider other more fundamental of our notions about vertebrate regulation and adaptation. (1) Although both marine and desert environments may be described as desiccating, the physiological adaptations required by these environments are completely different. (2) The inference from mammals that the kidney is the primary organ of osmoregulation is not supported in the cases of other vertebrate classes. (3) The capacity for accurate regulation of body water and solute levels does not necessarily imply that such homeostatic regulation occurs.
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Pseudemys nelsoni and Trachemys decussata inhabit brackish water in mainland areas of extreme southern Florida and on Grand Cayman Island. They appear to be intermediate in their salinity tolerance between truly freshwater forms and the highly specialized estuarine terrapin (Malaclemys). Unfed P. nelsoni (730-1240 g) had especially low rates of mass loss (primarily net water loss) in 100% sea water (about 0.4% initial mass/day). Smaller T. decussata (200-240 g) had higher values (about 0.8% /day), yet these rates were still lower than four values obtained on typical freshwater species (1.8-7.6% /day) held in 100% sea water. Mean whole body water effluxes in 100% sea water of adult P. nelsoni and T. decussata larger than 60 g were low (0.24-0.47 ml/100 g·h). Hatchling T. decussata had much higher rates of water efflux (1.0 ml/100 g·h). Sodium effluxes in 100% sea water were low (less than 100 μmol/100 g·h) in all size classes. There was no stimulation in sodium efflux after salt loading in P. nelsoni, nor in T. decussata after dehydration in saline solutions. This implies the lack of salt glands in these species. Sodium influx in 100% sea water was very low in adult P. nelsoni and in T. decussata larger than 200 g. There was a progressive increase in sodium influx with declining size in T. decussata, so that hatchlings underwent a considerable net uptake of sodium in sea water. Hatchling T. decussata fed fish ad libitum were unable to maintain mass or grow when the salinity exceeded 41% sea water. Juveniles of about 80 g grew at salinities up to 59% sea water, representing a significant increase in tolerance above that of the hatchlings. Additionally, 80 g turtles grew significantly faster in 25% sea water than in fresh water. Large individuals (>200 g) of both species tolerated immersion in 100% sea water for prolonged periods (at least 10-24 days). Their natural habitats vary seasonally in salinity, but remain on average quite dilute due to rainfall.
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The effect of salinity on survival, growth, haematological parameters and osmoregulation was evaluated in tambaqui. This study addressed two questions. Firstly, tambaqui (33.9 ± 3.4 g) reared in freshwater were subjected to gradual increases in salinity until 100% mortality. Two daily increments of salinity were tested with three replicates: 1 and 2 g L−1 day−1, while control group was kept in freshwater. For 1 g L−1 day−1, the first mortality appeared from a salinity of 11 g L−1 and the last dead fish was observed at a salinity of 20 g L−1, whereas for 2 g L−1 day−1, the mortalities occurred only between 20 and 22 g L−1. The main sub-lethal effects observed were food intake stopped, erratic swimming behaviour, increased mucus production and the dark pattern of pigmentation that appeared at 13 and 16 g L−1 for both treatments. Secondly, juveniles (57.4 ± 6.3 g) were reared at 0, 5, 10 and 15 g L−1, in triplicate, for 84 days. At the end of the experiment, the results indicated that the survival, growth, haematological parameters and osmoregulatory of fish were significantly affected by salinity. Survival was unaffected by 10 g L−1, whereas higher salinity (15 g L−1) had a detrimental effect. Differences in final weight, specific growth rates (SGR) and mean daily feed intake (MDFI) among treatments were significant. There were no significant trends in feed conversion rate (FCR) at salinities of 0, 5 and 10 ppt. In these salinities, FCR ranged between 1.2 ± 0.1 and 1.3 ± 0.1, whereas FCR at salinity of 15 g L−1 increased to 5.8 ± 4.4. At the end of the experiments, analysis of blood revealed that all haematological parameters were affected by increase in salinity. From the present investigation, it can be concluded that exposure to salinity significantly affects the survival, growth and physiological response of tambaqui.
Article
Osmotic adjustment is achieved by blood and intracellular fluids in the diamond-back terrapin when acclimatized either to fresh water or to sea water. The muscle adjusts its composition to a higher blood osmotic pressure by greater concentrations in ammonia, in taurine and in urea and to a lesser extent in all amino acids (aspartate excepted). The inorganic ion content is not affected. In the bladder mucosa ammonia, taurine and all amino acids are more concentrated in sea-water animals. But essentially urea is responsible for the higher osmotic pressure. Of the inorganic ions only potassium shows a (slight) increase in sea-water animals. In the colon mucosa there is a slight increase in the total amino acid content, in the concentrations of sodium and chloride, and a larger increase in urea. In the jejunum mucosa the concentrations of amino acids, urea and K are much higher in sea-water animals. The results are discussed within the framework of isosmotic regulation of intracellular fluids.
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Adaptation of cells to hypertonicity often involves changes in gene expression. Since the concentration of salt in the interstitial fluid surrounding renal inner medullary cells varies with operation of the renal concentrating mechanism and generally is very high, the adaptive mechanisms of these cells are of special interest. Renal medullary cells compensate for hypertonicity by accumulating variable amounts of compatible organic osmolytes, including sorbitol, myo-inositol, glycine betaine, and taurine. In this review we consider how these solutes help relieve the stress of hypertonicity and the nature of transporters and enzymes responsible for their variable accumulation. We emphasize recent developments concerning the molecular basis for osmotic regulation of these genes, including identification and characterization of osmotic response elements. Although osmotic stresses are much smaller in other parts of the body than in the renal medulla, similar mechanisms operate throughout, yielding important physiological and pathophysiological consequences.
Article
The Chinese soft-shelled turtle, Pelodiscus sinensis, is well adapted to aquatic environments, including brackish swamps and marshes. It is ureotelic, and occasionally submerges its head into puddles of water during emersion, presumably for buccopharyngeal respiration. This study was undertaken to test the hypothesis that the buccophyaryngeal cavity constitutes an important excretory route for urea in P. sinensis. Results indicate that a major portion of urea was excreted through the mouth instead of the kidney during immersion. When restrained on land, P. sinensis occasionally submerged their head into water (20-100 min), during which urea excretion and oxygen extraction occurred simultaneously. These results indicate for the first time that buccopharyngeal villiform processes (BVP) and rhythmic pharyngeal movements were involved in urea excretion in P. sinensis. Urea excretion through the mouth was sensitive to phloretin inhibition, indicating the involvement of urea transporters (UTs). In addition, saliva samples collected from the buccopharyngeal surfaces of P. sinensis injected intraperitoneally with saline contained ~36 mmol N l(-1) urea, significantly higher than that (~2.4 mmol N l(-1)) in the plasma. After intraperitoneal injection with 20 μmol urea g(-1) turtle, the concentration of urea in the saliva collected from the BVP increased to an extraordinarily high level of ~614 μmol N ml(-1), but the urea concentration (~45 μmol N ml(-1)) in the plasma was much lower, indicating that the buccopharyngeal epithelium of P. sinensis was capable of active urea transport. Subsequently, we obtained from the buccopharyngeal epithelium of P. sinensis the full cDNA sequence of a putative UT, whose deduced amino acid sequence had ~70% similarity with human and mouse UT-A2. This UT was not expressed in the kidney, corroborating the proposition that the kidney had only a minor role in urea excretion in P. sinensis. As UT-A2 is known to be a facilitative urea transporter, it is logical to deduce that it was localized in the basolateral membrane of the buccopharyngeal epithelium, and that another type of primary or secondary active urea transporter yet to be identified was present in the apical membrane. The ability to excrete urea through the mouth instead of the kidney might have facilitated the ability of P. sinensis and other soft-shelled turtles to successfully invade the brackish and/or marine environment.
Article
Summary1. Freshwater fishes are the most northerly of freshwater ectotherms, followed by frogs. North American freshwater snakes, turtles, and salamanders do not range farther north than southernmost Canada.2. Freezing and desiccation are the main challenges during terrestrial hibernation of ectotherms. Oxygen depletion, water balance, and ionic balance are the major problems for air breathing ectotherms that hibernate underwater.3. The importance of accumulation of energy stores for overwintering among fishes depends upon the length and severity of the winters, whether or not there is springtime reproduction, body size, latitude, and the availability and use of food during overwintering.4. Fishes can decrease energy demands during the winter by reductions in activity, metabolic depression, and entrance in semi-torpidity.5. Adaptations for coping with hypoxia and anoxia among overwintering freshwater fishes may include metabolic depression, a decrease in blood O2 affinity, microhabitat selection, air breathing, short-distance migration, biochemical modifications aimed at adjusting glycolytic rates, and alcoholic fermentation.6. Freshwater turtles have a worldwide northern limit of approximately 50° N, which means that some species spend about half of their lives hibernating.7. Aquatic turtles normally hibernate underwater, although occasionally they hibernate on land. In water they usually hibernate in a hypoxic or anoxic (mud) environment and in relatively shallow water. Wintertime movements of unknown frequency occur in some species.8. The hatchlings of many turtle species can overwinter in the nest. Among northern species this behaviour is most common among painted turtles, whose hatchlings can withstand freezing.9. Mortality among adult turtles is probably highest during the hibernation cycle.10. Temperature appears to the most important cue for entry and exit from hibernation among freshwater turtles.11. Little is known of the energetics of overwintering turtles. Energy stores for overwintering may be more important at lower latitudes than at higher ones, due to the higher metabolic rates of overwintering, but non-feeding, southern turtles.12. The ability of turtles to tolerate submergence is a function of temperature, degree of water oxygenation, latitude of origin, efficacy of extrapulmonary respiratory pathways, and metabolic rate.13. For turtles that hibernate in an anoxic hibernaculum, and for those without sufficient extrapulmonary uptake of O2 to allow metabolism to be completely aerobic, the most important physiological perturbation is an acidosis developed from a continuing production of lactate. If sufficient O2 can be obtained, the most likely factors limiting hibernation time are water balance and ion balance.14. Mechanisms of turtles for coping with acidosis include metabolic depression, integumental CO2 loss, bicarbonate buffering, and changes in ion concentrations that minimize the decrease in SID (strong ion difference). The most important among the latter are a decrease in plasma [Cl-] and large increases in plasma calcium and magnesium.15. Turtles are unique among reptiles in their ability to maintain both cardiovascular and nervous system function during prolonged anoxia.16. Turtles gain weight from water uptake during submerged hibernation, but apparently maintain some kidney function; however, osmoregulation is one of the least known areas of the physiology of hibernation.17. Recovery of turtles upon emergence commences with a rapid hyperventilatory compensation of pH, followed by a slower adjustment of ion levels. Basking speeds recovery greatly.18. While hibernation of turtles in the northern parts of their ranges is most likely very stressful physiologically, northern range limits are more likely to be determined by reproductive restraints than by the rigors of extended hibernation.19. The superior ability of turtles to tolerate anoxia may be more the result of an annual hibernation than of their diving habits during active periods of the year.20. Freshwater snakes usually hibernate on land. However, they appear to be capable of aquatic hibernation and may not do so because of the risk of death from anoxia.21. Some species of terrestrial snakes are known to hibernate underwater, and are able to do so in the laboratory for months. In the field, this behaviour is considered opportunistic, as there is no evidence to suggest that any snakes can tolerate extended anoxia.
1.1. Urine of normally hydrated green turtles was isosmotic relative to plasma (320 mOsm/kg).2.2. Green turtles kept out of water for 10–20 days produced urine with a mean concentration of 450 mOsm/kg; plasma concentration for these animals was 390 mOsm/kg.3.3. Mean urine composition of dehydrated animals was 16 mmol/1 Na+, 38 mmol/l K+, 2.4 mmol/1 Ca2+, 74 mmol/1 NH3, 5.8 mmol/1 Cl− and 34 mmol/1 urea. The balance of the urine composition presumably consists of unknown organic anions.4.4. Salt gland secretions were composed primarily of sodium and chloride ions and had a mean concentration of 1845 mOsm/kg for dehydrated animals; normally hydrated animals had a mean concentration of 768 mOsm/kg.
Article
The effects of isolation-related and vegetational parameters on presence and relative abundance of snakes in patchy forested fragments of Mediterranean central Italy are studied. The most abundant species was Coluber viridiflavus (accounting for 47.7% of the total snake sample observed) followed by Vipera aspis (22%), Elaphe longissima (21.5%), Natrix natrix (7.7%), and Coronella austriaca (1.1%). There was a clear trend for bigger species to be less distributed among the various forest fragments than the smaller species. Presence of Coluber viridiflavus, Coronella austriaca and Natrix natrix was not influenced by woodland area, whereas that of Vipera aspis and Elaphe longissima was positively influenced by woodland area. Woodland isolation parameters did not influence the presence of Coluber viridiflavus, Coronella austriaca and Natrix natrix, but of Vipera aspis and Elaphe longissima. Discriminant stepwise analysis suggested that specific environmental features influenced the occurrence and abundance of the various snake species, Vipera aspis being the taxon more affected by isolation-related parameters. Some conservation implications of our observations are also discussed.
Article
The blood of the diamondback terrapin going from fresh water to 50% sea water shows an increase in its osmotic pressure which is mainly due to an increase in Na and Cl concentrations. The blood of terrapins living in sea water compared with the blood of terrapins living in 50 % sea water shows a higher osmotic pressure which is the result solely of a higher urea concentration; Na and Cl concentrations are no longer affected in this second stage of adaptation. Urine of 50% sea-water terrapins and of sea-water terrapins is generally isosmotic to the blood while the urine of fresh-water terrapins is usually hypo-osmotic. The bladder appears to play an essential part in reducing water loss in the seawater terrapins but is not implicated in the salt balance. When each animal is considered individually, the urea concentration in the urine is always higher than in the serum, suggesting that the high urea concentration in the blood of terrapins adapted to sea water is due to an urea accumulation in the bladder.
Article
Plasma aldosterone concentration has been measured by radioimmunoassay in a tortoise species Testudo hermanni Gmelin. Control levels were very low, 8.26 ± 0.2 ng/100 ml, if compared with the determination carried out in other reptilian species with the same RIA method. A sodium-loaded diet for a prolonged period (30 days) depressed aldosterone levels but administration of a diuretic produced a significant elevation. Plasma aldosterone, sodium, and potassium concentrations were significantly correlated. Administration of a mammalian inhibitor of aldosterone (spironolactone) was not followed by a significant plasma aldosterone or electrolyte changes. These data are consistent in supporting the hypothesis that aldosterone is involved in hydromineral regulation, at least in terrestrial chelonians, with a direct action on the renal proximal tubule.
Article
Freshwater turtles, Chrysemys picta bellii, were submerged in groups of 7 at 3 degrees C in O2-free water for 1, 2, 4, 8 and 12 weeks. Blood samples from these turtles and from 10 normoxic turtles at 3 degrees C were analyzed for plasma concentrations of lactic acid, total CO2, Na+, K+, Cl-, Ca2+, total calcium, total magnesium and osmolality. Total lactate rose during anoxia to a mean peak value of 145 mM, but the decrease in HCO-3 and Cl- and increase in K+ balanced less than 40% of the lactate. Total calcium and total magnesium rose respectively by 9.5 and 6.0 times the normoxic values after 12 weeks, at which time free [Ca2+] was 25.0 mEq (37% of the total calcium). To evaluate the possible role of bound calcium in ion balance, test solutions with calcium, but with and without 145 mM lactate, were tested for free Ca2+. In the presence of lactate, over two-thirds of the total calcium combined with lactate- to form a calcium lactate complex (possibly CaLactate+). Based on these data, it is concluded that most of the bound plasma calcium in the anoxic turtles was combined with lactate. By assuming that magnesium reacts similarly with lactate, a complete account of plasma ion balance is accomplished and the turtle's plasma ionic response to extreme lactic acidosis is described. Plasma osmolality increased during anoxia by 100 mOsm and matched the mM rise in total measured and calculated ions.
Article
Eastern painted turtles (Chrysemys picta picta) from Connecticut were submerged at 3 degrees C in normoxic and anoxic water to simulate potential respiratory environments within their hibernacula. Those in normoxic water could survive submergence for at least 150 d, while those in anoxic water could survive for a maximum of about 125 d. Turtles in normoxic water developed a slight metabolic acidosis as plasma lactate accumulated to about 50 mM in 150 d, while anoxic turtles developed a severe lactic acidosis as plasma lactate reached about 200 mM in 125 d; there was no respiratory acidosis in either group. Plasma [Na+] changed little in either group, [Cl-] fell by about one-third in both, and [K+] increased by about fourfold in anoxic turtles but only slightly in those in normoxic water. Total plasma magnesium and calcium increased profoundly in anoxic turtles but moderately in those in normoxic water. Consideration of charge balance indicates that all major ions were measured in both groups. Plasma glucose remained unchanged in anoxic turtles until after about 75 d of submergence, when it increased and continued to increase with the duration of anoxia, with much variation among individuals; glucose remained unchanged throughout in turtles in normoxic water. Hematocrit doubled in 150 d in turtles in normoxic water; in anoxic turtles, an initial increase was no longer significant by day 100. Plasma osmolality increased markedly in anoxic turtles, largely because of accumulation of lactate, but anoxic turtles only gained about half the mass of turtles in normoxic water, who showed no increase in osmolality. The higher weight gain in the latter group is attributed to selective perfusion and ventilation of extrapulmonary gas exchange surfaces, resulting in a greater osmotic influx of water. The physiologic responses to simulated hibernation of C. picta picta are intermediate between those of Chrysemys picta bellii and Chrysemys picta dorsalis, which correlates with the severity of the winter each subspecies would be expected to encounter.
Article
Many aquatic turtles possess paired evaginations of the cloaca called cloacal bursae. Despite more than two centuries of study, little consensus exists as to the function(s) of these organs. We tested a recent suggestion that bursae could function in water uptake ("cloacal drinking"). Turtles (Trachemys scripta) were dehydrated (68-86% of maximum body mass) and given the opportunity to drink orally or cloacally. Dehydration caused increases in hematocrit and osmolality of extracellular fluid (ECF), but only after loss of 10-12% of maximum body mass, suggesting that turtles osmoregulated by reabsorbing water from the urinary bladder. Turtles drank eagerly when they could submerge their heads, and drinking was accompanied by an increase in body mass and a decrease in ECF osmolality. However, dehydrated turtles with tail and anus submerged showed no changes in mass or osmolality, suggesting that water absorption is not a significant function of the cloacal bursae in this species. Evidence for other putative functions is reviewed, leading to a pluralistic view: in cryptodires, bursae apparently function primarily in buoyancy control and secondarily in ion transport and nesting, but several pleurodires have been shown recently to use them in aquatic respiration.
Article
This study aimed to determine effects of 6-day progressive increase in salinity from 1 per thousand to 15 per thousand on nitrogen metabolism and excretion in the soft-shelled turtle, Pelodiscus sinensis. For turtles exposed to 15 per thousand water on day 6, the plasma osmolality and concentrations of Na+, Cl- and urea increased significantly, which presumably decreased the osmotic loss of water. Simultaneously, there were significant increases in contents of urea, certain free amino acids (FAAs) and water-soluble proteins that were involved in cell volume regulation in various tissues. There was an apparent increase in proteolysis, releasing FAAs as osmolytes. In addition, there might be an increase in catabolism of certain amino acids, producing more ammonia. The excess ammonia was retained as indicated by a significant decrease in the rate of ammonia excretion on day 4 in 15 per thousand water, and a major portion of it was converted to urea. The rate of urea synthesis increased 1.4-fold during the 6-day period, although the capacity of the hepatic ornithine urea cycle remained unchanged. Urea was retained for osmoregulation because there was a significant decrease in urea excretion on day 4. Increased protein degradation and urea synthesis implies greater metabolic demands, and indeed turtles exposed to 15 per thousand water had significantly higher O2 consumption rate than the freshwater (FW) control. When turtles were returned from 15 per thousand water to FW on day 7, there were significant increases in ammonia (probably released through increased amino acid catabolism) and urea excretion, confirming that FAAs and urea were retained for osmoregulatory purposes in brackish water.