Salinity tolerances of two Australian freshwater turtles,<i>Chelodina expansa</i>and<i>Emydura macquarii</i>(Testudinata: Chelidae)

Bower, Deborah S.; Scheltinga, D. M.; Clulow, Simon; Clulow, John; Franklin, Craig E.; Georges, Arthur

doi:10.1093/conphys/cow042

Cited by 28 publications

(41 citation statements)

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“…Furthermore, populations of B. borneoensis , a species that frequently occurs in estuarine habitats of SE Asia, survived for at least 14 days in 100% seawater (Dunson & Moll, ), and populations of Pseudemys nelsoni , a habitat generalist of the southeastern USA, tolerated 100% seawater for up to 24 days (Dunson & Seidel, ). In addition, the Chinese softshell turtle ( Pelodiscus sinensis ) appears to be tolerant of increased salinity for short periods, as it survived in up to 50% seawater (17.5‰ salinity) for up to a week (Lee et al, ); similarly, the largest of the long‐necked turtles, C. expansa, survived at 15‰ for 50 days (Bower et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…Flexible behaviour of multiple freshwater turtle species in the absence of physiological adaptations allows them to temporarily occupy brackish water environments (Greenberg & Maldonado, ). Behavioural mechanisms include activities like movements between saline and freshwater areas, frequent retreats to freshwater sources higher upstream, and reduced feeding and drinking that would result in ingestion of higher salinity water (Hart & Lee, ; Harden, Midway, & Williard, ; Bower et al, ). For example, M. terrapin and B. baska can identify high‐salinity conditions and avoid drinking or feeding when water salinity is too high (Davenport & Ward, ).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, ranges may have shifted more recently into saline environments, generating contemporary brackish water records (Kukushkin & Jablonski, ). Furthermore, in Australia, wide‐ranging aquatic turtles found in large catchments tolerating expanses of saline conditions reflects an extensive history of evolutionary adaption to salinity as well as a recent adaptation to dry periods (Bower et al, ). During extended periods of drought, freshwater turtles could have been isolated in ponds with high salinity, forcing these turtles to adapt or perish (Bower et al, ).…”

Section: Resultsmentioning

confidence: 99%

“…Behavioural strategies allow some vertebrates to reduce the physiological impact of saline conditions (e.g. 0.5–35‰; Remane & Schlieper, ), and these can include moving along salinity gradients, drinking fresh water from surface sources, and reducing feeding (Greenberg et al, ; Bower et al, ). Other freshwater fauna have morphological and physiological adaptations (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Other freshwater fauna have morphological and physiological adaptations (e.g. salt glands, regulation of blood, urea, and intercellular fluids) that enable them to tolerate, rather than avoid, saline conditions (Gray, ; Bower et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Salinity tolerances and use of saline environments by freshwater turtles: implications of sea level rise

et al. 2018

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The projected rise in global mean sea levels places many freshwater turtle species at risk of saltwater intrusion into freshwater habitats. Freshwater turtles are disproportionately more threatened than other taxa; thus, understanding the role of salinity in determining their contemporary distribution and evolution should be a research priority. Freshwater turtles are a slowly evolving lineage; however, they can adapt physiologically or behaviourally to various levels of salinity and, therefore, temporarily occur in marine or brackish environments. Here, we provide the first comprehensive global review on freshwater turtle use and tolerance of brackish water ecosystems. We link together current knowledge of geographic occurrence, salinity tolerance, phylogenetic relationships, and physiological and behavioural mechanisms to generate a baseline understanding of the response of freshwater turtles to changing saline environments. We also review the potential origins of salinity tolerance in freshwater turtles. Finally, we integrate 2100 sea level rise (SLR) projections, species distribution maps, literature gathered on brackish water use, and a phylogeny to predict the exposure of freshwater turtles to projected SLR globally. From our synthesis of published literature and available data, we build a framework for spatial and phylogenetic conservation prioritization of coastal freshwater turtles. Based on our literature review, 70 species (∼30% of coastal freshwater turtle species) from 10 of the 11 freshwater turtle families have been reported in brackish water ecosystems. Most anecdotal records, observations, and descriptions do not imply long-term salinity tolerance among freshwater turtles. Rather, experiments show that some species exhibit potential for adaptation and plasticity in physiological, behavioural, and life-history traits that enable them to endure varying periods (e.g. days or months) and levels of saltwater exposure. Species that specialize on brackish water habitats are likely to be vulnerable to SLR because of their exclusive coastal distributions and adaptations to a narrow range of salinities. Most species, however, have not been documented in brackish water habitats but may also be highly vulnerable to projected SLR. Our analysis suggests that approximately 90% of coastal freshwater turtle species assessed in our study will be affected by a 1-m increase in global mean SLR by 2100. Most at risk are freshwater turtles found in New Guinea, Southeast Asia, Australia, and North and South America that may lose more than 10% of their present geographic range. In addition, turtle species in the families Chelidae, Emydidae, and Trionychidae may experience the greatest exposure to projected SLR in their present geographic ranges. Better understanding of survival, growth, reproductive and population-level responses to SLR will improve region-specific population viability predictions of freshwater turtles that are increasingly exposed to SLR. Integrating phylogenetic, physiological, and spatial frameworks t...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Salinity tolerances and use of saline environments by freshwater turtles: implications of sea level rise

et al. 2018

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Osmoregulation by Vertebrates in Aquatic Environments

Lillywhite

Evans

2021

Encyclopedia of Life Sciences

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Because the salt concentration of body fluids in aquatic vertebrates differs from that of their environment, they face net influx or efflux of water and salt across their permeable skin or exposed membranes. In fishes, these diffusional movements of both salts and water largely involve the gills. Other vertebrates have less permeable body surfaces, but water and salts are gained in drinking that is incidental to eating prey, which also can be an important source of salt intake. Kidneys function importantly in freshwater fishes to remove excess water, and ions are actively transported inwards across gill tissue as well as acquired in food. Marine fishes tend to dehydrate in seawater, so they drink seawater to make up a water deficit and secrete excess salt across the gills. Marine elasmobranch fishes accumulate urea in body fluids to minimise the gradient for osmotic exchange and secrete excess ions via a specialised rectal gland that functions accessory to the kidney. In other vertebrates, inhabitants of fresh water must counteract a key problem of acquiring sufficient ions while excreting nitrogenous waste as ammonia or urea, whereas marine species must avoid excess salt intake while avoiding dehydration. Vertebrates without gills have evolved either extrarenal salt glands that excrete excess salt, or in the case of mammals, a specialised kidney that can excrete highly concentrated urine. Relatively few, non‐fish taxa drink seawater as a route for water gain, while most others have dependency on dietary, metabolic or free drinking water. Osmoregulation involves the maintenance of volume, distribution and ionic composition of body fluids in organisms. With the exception of hagfish, extant vertebrates maintain osmotic concentrations of body fluids at levels that are roughly one‐third that of seawater. Aquatic vertebrates living in fresh water must counteract excessive influx of water and losses of ions to the surrounding environment, whereas those living in marine environments tend to dehydrate and gain excess salt. Freshwater fishes eliminate excess water by means of producing a copious flow of dilute urine, while acquiring ions from surrounding water by transporter mechanisms located in the gills. Marine fishes acquire needed water by drinking seawater and excreting excess salt gained by diffusion and drinking by transport mechanisms in the gills. Marine vertebrates other than fishes and mammals have evolved extrarenal salt glands that excrete excess salts, and water is gained largely from dietary, metabolic and freshwater drinking sources. Marine mammals excrete salt loads and urea from kidneys that have effective concentrating abilities, while gaining water from diet and metabolism.

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Abundance and nutritional status of freshwater turtles to guide delivery of environmental flows in the Murray‐Darling Basin, south‐eastern Australia

Francis

Brandis

Chessman

2022

Aquatic Conservation

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Almost half of Australian freshwater turtle species are formally listed as threatened, but little is known about the effects of water management and other factors on the abundance and health of freshwater turtles in arid and semi‐arid regions. This study investigated how river flows (including the controlled release of water from an upstream storage facility, or ‘environmental flow’) and water quality might affect the abundance and nutritional status of three freshwater turtle species in three dryland rivers of the Murray–Darling basin in south‐eastern Australia. No response in abundance or nutritional status of the broad‐shelled turtle, Chelodina expansa, the eastern long‐necked turtle, Chelodina longicollis, and the Macquarie turtle, Emydura macquarii, was detected in relation to river flows, possibly because of the small magnitude of the environmental flow. However, for C. expansa, the catch per unit effort (CPUE) was negatively related to increasing macrophyte cover, electrical conductivity (EC, an indicator of salinity), and turbidity. CPUE for C. longicollis was positively related to macrophyte cover and EC, and for E. macquarii it was positively related to macrophyte cover. Haematological measurements suggested that the turtles had healthy nutritional status. Body condition and blood glucose and protein were related significantly to EC, whereas haematological measurements varied significantly among species and between spring and summer. The main conclusion is that water management measures to help the conservation of these turtles should include sufficient environmental flow to produce overbank flooding, thereby creating and maintaining a wide range of habitat suitable for the differing needs of the individual species.

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Salinity tolerances of two Australian freshwater turtles,Chelodina expansaandEmydura macquarii(Testudinata: Chelidae)

Abstract: Two species of Australian freshwater turtle were submerged in either water of 0‰ or 15‰ over 50 days. Turtles in 15‰ water reduced feeding and had raised plasma ionic concentrations of sodium, chloride, urea and uric acid to decrease dehydration and enable survival.

Cited by 28 publications

References 38 publications

Salinity tolerances and use of saline environments by freshwater turtles: implications of sea level rise

Salinity tolerances and use of saline environments by freshwater turtles: implications of sea level rise

Osmoregulation by Vertebrates in Aquatic Environments

Abundance and nutritional status of freshwater turtles to guide delivery of environmental flows in the Murray‐Darling Basin, south‐eastern Australia

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