Food abundance and diet variation in freshwater turtles from the mid-Murray River, Australia

2018 ◽  
Vol 66 (1) ◽  
pp. 67 ◽  
Author(s):  
Kristen Petrov ◽  
Jessica Lewis ◽  
Natasha Malkiewicz ◽  
James U. Van Dyke ◽  
Ricky-John Spencer
Keyword(s):  
Green Algae ◽  
Prey Availability ◽  
Foraging Strategies ◽  
Freshwater Turtles ◽  
Food Items ◽  
Filamentous Green Algae ◽  
Invertebrate Diversity ◽  
Murray River ◽  
Specialist Species ◽  
Chelodina Longicollis

Consumers usually respond to variations in prey availability by altering their foraging strategies. Generalist consumers forage on a diversity of resources and have greater potential to ‘switch’ their diet in response to fluctuations in prey availability, in comparison to specialist consumers. We aimed to determine how the diets of two specialist species (the eastern long-necked turtle (Chelodina longicollis) and the broad-shelled turtle (Chelodina expansa) and the more generalist Murray River short-necked turtle (Emydura macquarii) respond to variation in habitat and prey availability. We trapped and stomach-flushed turtles, and compared their diets along with environmental variables (turbidity, macrophyte and filamentous green algae cover, and aquatic invertebrate diversity and abundance) at four wetlands in north-central Victoria. Diets of E. macquarii differed from those of both Chelodina species, which overlapped, across all four sites. However, samples sizes for the two Chelodina species were too small to compare among-wetland variation in diet. Dietary composition of E. macquarii was variable but did not differ statistically among sites. Emydura macquarii preferentially selected filamentous green algae at three of the four sites. Where filamentous green algae were rare, total food bolus volume was reduced and E. macquarii only partially replaced it with other food items, including other vegetation, wood, and animal prey. Many turtles at these sites also had empty stomachs. Thus, filamentous green algae may be a limiting food for E. macquarii. Although E. macquarii has previously been described as a generalist, it appears to have limited ability to replace filamentous green algae with other food items when filamentous green algae are rare.

Ecological and physiological impacts of salinisation on freshwater turtles of the lower Murray River

2012 ◽  
Vol 39 (8) ◽  
pp. 705 ◽  
Author(s):  
Deborah S. Bower ◽  
Clare E. Death ◽  
Arthur Georges
Keyword(s):  
Saline Lake ◽  
South Australia ◽  
Freshwater Turtle ◽  
Plasma Sodium ◽  
Freshwater Species ◽  
Freshwater Turtles ◽  
Brackish Lake ◽  
Ecological Processes ◽  
Murray River ◽  
Chelodina Longicollis

Context The increasing intensity and extent of anthropogenically mediated salinisation in freshwater systems has the potential to affect freshwater species through physiological and ecological processes. Determining responses to salinisation is critical to predicting impacts on fauna. Aims We aimed to quantify the response of wild-caught turtles from freshwater lakes that had become saline in the lower Murray River catchment. Methods Plasma electrolytes of all three species of freshwater turtle from South Australia were compared among two freshwater sites (Horseshoe Lagoon and Swan Reach), a brackish lake (Lake Bonney) and a saline lake (Lake Alexandrina). Key results Chelodina longicollis, C. expansa and Emydura macquarii from a brackish lake had higher concentrations of plasma sodium and chloride than those from freshwater habitats. However, osmolytes known to increase under severe osmotic stress (urea and uric acid) were not elevated in brackish sites. Turtles from the highly saline lake were colonised by an invasive marine worm which encased the carapace and inhibited limb movement. Conclusions Freshwater turtles in brackish backwaters had little response to salinity, whereas the C. longicollis in a saline lake had a significant physiological response caused by salt and further impacts from colonisation of marine worms. Implications Short periods of high salinity are unlikely to adversely affect freshwater turtles. However, secondary ecological processes, such as immobilisation from a marine worm may cause unexpected impacts on freshwater fauna.

Road mortality of the eastern long-necked turtle (Chelodina longicollis) along the Murray River, Australia: an assessment using citizen science

2018 ◽  
Vol 66 (1) ◽  
pp. 41 ◽  
Author(s):  
Claudia Santori ◽  
Ricky-John Spencer ◽  
James U. Van Dyke ◽  
Michael B. Thompson
Keyword(s):  
Citizen Science ◽  
Management Practices ◽  
Habitat Destruction ◽  
Road Mortality ◽  
Freshwater Turtles ◽  
Introduced Predators ◽  
Murray River ◽  
Time Of Year ◽  
Rain Events ◽  
Chelodina Longicollis

Turtles face a variety of threats (e.g. habitat destruction, introduced predators) that are pushing many species towards extinction. Vehicle collisions are one of the main causes of mortality of adult freshwater turtles. To conceptualise the level of threat that roads pose to Australians turtles, we analysed data gathered through the citizen science project TurtleSAT along the Murray River. We recorded 124 occurrences of turtle road mortality, which included all three local species (Chelodina expansa, Chelodina longicollis, and Emydura macquarii). Chelodina longicollis was the most commonly reported species killed on roads. We found that rain and time of year affect the likelihood of C. longicollis being killed on roads: increased turtle mortality is associated with rain events and is highest during the month of November, which coincides with their nesting season. Chelodina longicollis was most likely to be killed on the Hume Highway and roads around major urban centres; therefore, we recommend that governing bodies focus management practices and increase awareness at these locations. The degree of road mortality that we detected in this study requires mitigation, as it may contribute to the decline of C. longicollis along the Murray River.

Declines of freshwater turtles associated with climatic drying in Australia

2011 ◽  
Vol 38 (8) ◽  
pp. 664 ◽  
Author(s):  
Bruce C. Chessman
Keyword(s):  
River Flow ◽  
Freshwater Turtle ◽  
Severe Drought ◽  
Freshwater Turtles ◽  
Catch Per Unit Effort ◽  
Unit Effort ◽  
Murray River ◽  
Floodplain Inundation ◽  
Global Impacts ◽  
Chelodina Longicollis

Context While much attention has been paid to the effects of global temperature increases on the geographical ranges and phenologies of plants and animals, less is known about the impacts of climatically driven alteration of water regimes. Aims To assess how three species of freshwater turtle in Australia’s Murray–Darling Basin have responded to long-term decline in river flow and floodplain inundation due to climatic drying and water diversions. Methods Turtle populations were sampled in a section of the Murray River and its floodplain in 1976–82 following a wet period and in 2009–11 at the end of the most severe drought on record. Catch per unit effort, proportional abundance in different habitat types and population structure were assessed in both periods. Key results Catch per unit effort in baited hoop nets declined by 91% for the eastern snake-necked turtle (Chelodina longicollis) and 69% for the Murray turtle (Emydura macquarii), but did not change significantly for the broad-shelled turtle (Chelodina expansa). In addition, total catches from a range of sampling methods revealed a significantly reduced proportion of juvenile C. longicollis and E. macquarii in 2009–11, suggesting a fall in recruitment. Key conclusions The decline of C. longicollis was likely due mainly to drought-induced loss of critical floodplain habitat in the form of temporary water bodies, and that of E. macquarii to combined effects of drought and predation on recruitment. C. expansa seems to have fared better than the other two species because it is less vulnerable to nest predation than E. macquarii and better able than C. longicollis to find adequate nutrition in the permanent waters that remain during extended drought. Implications Declining water availability may be a widespread threat to freshwater turtles given predicted global impacts of climate change and water withdrawals on river flows. Understanding how each species uses particular habitats and how climatic and non-climatic threats interact would facilitate identification of vulnerable populations and planning of conservation actions.

scholarly journals Urban mosquitoes and filamentous green algae: their biomonitoring role in heavy metal pollution in open wastewater channels in Nairobi, Kenya

2021 ◽  
Author(s):  
Geoffrey Kariuki Kinuthia ◽  
Veronica Ngure ◽  
Luna Kamau
Keyword(s):  
Heavy Metals ◽  
Green Algae ◽  
Toxic Elements ◽  
Tap Water ◽  
Aquatic Organisms ◽  
Industrial Area ◽  
Metal Exposure ◽  
Water Control ◽  
Filamentous Green Algae ◽  
Us Epa

Abstract Background Levels of Mercury (Hg), Lead (Pb), Chromium (Cr), Cadmium (Cd), Thallium (Tl), and Nickel (Ni) in samples of wastewater, filamentous green algae (spirogyra) and urban mosquitoes obtained from open wastewater channels in Nairobi industrial area, Kenya, was established. Industrial wastewater may contain hazardous heavy metals upon exposure. Aquatic organisms in wastewater may accumulate the toxic elements with time. Therefore, human population living in informal settlements in Nairobi industrial area risk exposure to such toxic elements. Biomonitoring using aquatic organisms can be key in metal exposure assessment. Results Pb, Cr, & Ni levels ranged from 3.08 to 15.31 µg/L while Tl, Hg, & Cd levels ranged from 0.05 to 0.12 µg/L in wastewater. Pb, Cr, Ni, & Cd levels were above WHO, Kenya & US EPA limits for wastewater but Hg was not. Metals in tap water (control) which ranged from 0.01 to 0.2 µg/L was below WHO, US EPA, & Kenya standard limits. Pb, Cr, Tl, & Ni levels in assorted field mosquitoes were 1.3 to 2.4 times higher than in assorted laboratory-reared mosquitoes. Hg & Cd concentrations in laboratory-reared mosquitoes (0.26 mg/L & 1.8 mg/L respectively) was higher than in field mosquitoes (0.048 mg/L & 0.12 mg/L respectively). Pb, Cr, Ni, & Cd levels in green filamentous algae were 110.62, 29.75, 14.45, & 0.44 mg/L respectively and above WHO limits for vegetable plants. Hg level in algae samples (0.057 mg/L) was below WHO standard limits but above Kenya & US EPA limits in vegetables. Correlations for Pb & Hg (r = 0.957; P < 0.05); Cd & Cr (r = 0.985; P < 0.05) in algae samples were noted. The metal concentrations in the samples were in the order, wastewater < mosquitoes < filamentous green algae. Conclusion Samples of wastewater, mosquitoes and filamentous green algae from open wastewater channels and immediate vicinity, in Nairobi industrial area (Kenya) contained Hg, Pb, Cr, Cd, Tl, and Ni. Urban mosquitoes and filamentous green algae can play a role of metal biomonitoring in wastewater. The possibility of urban mosquitoes transferring the heavy metals to their hosts when sucking blood should be investigated.

Foraging modes of carnivorous plants

2019 ◽  
Vol 66 (1-2) ◽  
pp. 101-112 ◽  
Author(s):  
Aaron M. Ellison
Keyword(s):  
Prey Availability ◽  
Soil Nutrient ◽  
Optimal Foraging Theory ◽  
Foraging Theory ◽  
Carnivorous Plants ◽  
Foraging Strategies ◽  
Nutrient Concentrations ◽  
Future Research ◽  
Single Location ◽  
Foraging Modes

Abstract Carnivorous plants are pure sit-and-wait predators: they remain rooted to a single location and depend on the abundance and movement of their prey to obtain nutrients required for growth and reproduction. Yet carnivorous plants exhibit phenotypically plastic responses to prey availability that parallel those of non-carnivorous plants to changes in light levels or soil-nutrient concentrations. The latter have been considered to be foraging behaviors, but the former have not. Here, I review aspects of foraging theory that can be profitably applied to carnivorous plants considered as sit-and-wait predators. A discussion of different strategies by which carnivorous plants attract, capture, kill, and digest prey, and subsequently acquire nutrients from them suggests that optimal foraging theory can be applied to carnivorous plants as easily as it has been applied to animals. Carnivorous plants can vary their production, placement, and types of traps; switch between capturing nutrients from leaf-derived traps and roots; temporarily activate traps in response to external cues; or cease trap production altogether. Future research on foraging strategies by carnivorous plants will yield new insights into the physiology and ecology of what Darwin called “the most wonderful plants in the world”. At the same time, inclusion of carnivorous plants into models of animal foraging behavior could lead to the development of a more general and taxonomically inclusive foraging theory.

Direct and indirect toxic effects of cotton-derived cellulose nanofibres on filamentous green algae

2015 ◽  
Vol 122 ◽  
pp. 399-405 ◽  
Author(s):  
Michele Munk ◽  
Humberto M. Brandão ◽  
Sophie Nowak ◽  
Ludovic Mouton ◽  
Juliana C. Gern ◽  
...  
Keyword(s):  
Green Algae ◽  
Toxic Effects ◽  
Filamentous Green Algae ◽  
Cellulose Nanofibres

Long- versus short-range foraging strategies of hoary (Lasiurus cinereus) and silver-haired (Lasionycteris noctivagans) bats and the consequences for prey selection

1985 ◽  
Vol 63 (11) ◽  
pp. 2507-2515 ◽  
Author(s):  
Robert M. R. Barclay
Keyword(s):  
Short Range ◽  
Prey Availability ◽  
Prey Selection ◽  
Foraging Strategy ◽  
Foraging Strategies ◽  
Lasiurus Cinereus ◽  
Echolocation Calls ◽  
Straight Line ◽  
Lasionycteris Noctivagans ◽  
Selection Of

Habitat use, temporal activity, foraging behaviour, and prey selection of hoary bats (Lasiurus cinereus) and silver-haired bats (Lasionycteris noctivagans) were studied at Delta Marsh, Manitoba. Bat activity was assessed by monitoring echolocation calls with ultrasonic detectors. Prey availability was determined using sticky and Malaise traps and dietary information was obtained from fecal analysis. Both species were active all night and foraged primarily in the lee of a narrow forested ridge. Lasionycteris noctivagans foraged in a manner that indicates that it detects and pursues prey over short distances. These bats fly slowly, are highly manoeuverable, and were commonly observed feeding on swarms of insects in small clearings. They use echolocation calls that support the notion of a short-range foraging strategy and feed opportunistically on whatever insects are available. Lasiurus cinereus, on the other hand, uses a long-range prey detection and pursuit foraging strategy. They fly rapidly along straight line paths in open areas and use echolocation calls designed to detect insects at a distance. The diet consists primarily of large insects (moths, beetles, and dragonflies), but the bats nonetheless feed opportunistically. The foraging strategy likely restricts the availability and profitability of small insects as prey.

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