Effect of water temperature and oxygen levels on the diving behavior of two freshwater turtles: Rheodytes leukops and Emydura macquarii

Rheodytes leukops is a bimodally respiring turtle that extracts oxygen from the water chiefly via two enlarged cloacal bursae that are lined with multi-branching papillae. The diving performance of R. leukops was compared to that of Emydura macquarii, a turtle with a limited ability to acquire aquatic oxygen. The diving performance of the turtles was compared under aquatic anoxia (0 mmHg), hypoxia (80 mmHg) and normoxia (155 mmHg) at 15, 23, and 30degreesC. When averaged across all temperatures the dive duration of R. leukops more than doubled from 22.4 +/- 7.65 min under anoxia to 49.8 +/- 19.29 min under normoxic conditions. In contrast, aquatic oxygen level had no effect on the dive duration of E. macquarii. Dive times for both species were significantly longer at the cooler temperature, and the longest dive recorded for each species was 538 min and 166 min for R. leukops and E. macquarii, respectively. Both species displayed a pattern of many short dives punctuated by occasional long dives irrespective of temperature or oxygen regime. Rheodytes leukops, on average, spent significantly less time (42 +/- 2 sec) at the surface per surfacing event than did E. macquarii (106 +/- 20 sec); however, surface times for both species were not related to either water temperature or oxygen level.

Incubation of Rigid-shelled Turtle Eggs: do Hydric Conditions Matter?

Rigid-shelled eggs of the broad-shelled river turtle Chelodina expansa were incubated at 28 degreesC in wet (-100 kPa), intermediate (-350 kPa) and dry (-750 kPa) conditions. Incubation period was influenced by clutch of origin, but was independent of incubation water potential. Rates of water gained from the environment and pre-pipping egg mass were influenced by incubation water potential - eggs incubating at higher (less negative) water potentials absorbing more water from their environment. Hatchlings from wet conditions had greater mass but a smaller amount of residual yolk than hatchlings from dry conditions and it is suggested that the amount of yolk converted to tissue is influenced by the amount of water absorbed by the egg during incubation. Water content of yolk-free hatchlings from the -100-kPa treatment was greater than those from the 350-kPa and -750-kPa treatments, but the water content of residual yolks was similar across all hydric conditions.

Seasonal changes in the diving performance of the bimodally respiring freshwater turtle Rheodytes leukops in a natural setting

The objective of this study was to investigate how seasonally fluctuating environmental conditions influence the diving performance of the highly aquatic, bimodally respiring turtle Rheodytes leukops in a natural setting. Over four consecutive seasons (Austral autumn 2000 to summer 2001), the diving behaviour of adult turtles was recorded via pressure-sensitive time-depth recorders within Marlborough Creek, central Queensland, Australia. Short surfacing intervals recorded for R. leukops in winter suggest that the species utilizes aquatic respiration as an overwintering strategy to prevent the development of a metabolic acidosis during the long inactive dives observed during the season. As water temperature increases and aquatic P-O 2 decreases, R. leukops switches from facultative to obligate air-breathing, presumably because of the increased metabolic cost associated with aquatic respiration under summer conditions. Increases in mean surfacing time from winter to spring and summer are attributed to seasonal changes in behaviour possibly associated with foraging rather than to the physiological state of the turtle, given that no difference in median surfacing time among seasons was observed.

Seasonal changes in the diel surfacing behaviour of the bimodally respiring turtle Rheodytes leukops

The purpose of this study was to determine whether a relationship existed between the diel surfacing trends of the bimodally respiring freshwater turtle Rheodytes leukops and daily fluctuations in specific biotic and abiotic factors: The, diel surfacing behaviour of adult R. leukops was recorded over four consecutive seasons (Austral autumn 2000 - summer 2001) within Marlborough Creek, central Queensland, Australia, using pressure-sensitive time-depth recorders. Additionally, diurnal variations in water temperature and aquatic Po-2 level, as well as the turtle's behavioural state (i.e., active versus resting), were monitored. In autumn and summer, surfacing frequency increased significantly during the daylight hours, with peak levels normally occurring around dawn (0500-0700) and. dusk (1700-1900). However, no consistent diel surfacing trend was recorded, for the turtles in winter or spring, owing to considerable variation among individual R. leukops. Diurnal surfacing trends recorded for R. leukops in, autumn and summer are attributed to periods of increased activity (possibly associated with foraging) during the daylight hours and not to daily variations in water temperature or aquatic Po-2 level. Turtles generally remained at a depth greater than 1 m throughout the day, where the effect of diel fluctuations in water temperature, (

Blood-respiratory and acid-base changes during extended diving in the bimodally respiring freshwater turtle Rheodytes leukops

Changes in blood-gas, acid-base, and plasma-ion status were investigated in the bimodally respiring turtle, Rheodytes leukops, during prolonged dives of up to 12 h. Given that R. leukops routinely submerges for several hours, the objective of this study was to determine whether voluntarily diving turtles remain aerobic and simultaneously avoid hypercapnic conditions over increasing dive lengths. Blood PO2, PCO2, and pH, as well as plasma concentrations of lactate, glucose, Na+, K+, Cl-, total Ca, and total Mg were determined in venous blood collected from the occipital sinus. Blood PO2 declined significantly with dive length; however, oxy-haemoglobin saturation remained greater than 30% for all R. leukops sampled. No changes were observed in blood PCO2, pH, [HCO3-], or plasma glucose, with increasing dive length. Despite repeated dives lasting more than 2 h, plasma lactate remained less than 3 mmol l(-1) for all R. leukops sampled, indicating the absence of anaerobiosis. Compensatory acid-base adjustments associated with anaerobiosis (e.g. declining [Cl-], increasing total [Ca] and [Mg]) were likewise absent, with plasma-ion concentrations remaining stable with increasing dive length. Results indicate that R. leukops utilises aquatic respiration to remain aerobic during prolonged dives, thus effectively avoiding the development of a metabolic and respiratory acidosis.

Patterns of lipid storage and mobilisation in the female green sea turtle (Chelonia mydas)

Reproductive data from southern Queensland indicate that vitellogenesis in female Chelonia mydas takes approximately 8 months and is followed by a migration to a breeding area. At Heron Island, females lay multiple clutches over approximately 3 months. To investigate how females mobilise and store lipid during the breeding season we collected plasma, yolk, and fat tissue samples from females at a variety of stages during the nesting season. In breeding females, concentrations of plasma triglyceride increased seasonally. They reached peak concentrations during vitellogenesis and courtship, remained high throughout the nesting season, and then declined to a nadir after the last clutch. Plasma protein concentration increased throughout the breeding season, peaking following the last clutch for the season. Yolk lipids were highest during courtship and were similar throughout the nesting season, suggesting that uptake of lipid by ovarian follicles is completed prior to the beginning of the nesting season. Plasma triglyceride decreases in females with prolonged periods of unsuccessful nesting, and total lipid levels in adipose tissue and follicle yolks were significantly lower in atretic females. It appears that: (1) endogenous energy reserves can be reduced by stochastic environmental events (such as those reducing nesting success), and (2) a metabolic shift signalling the end of the nesting season is characterised by a drop in plasma triglycerides and slight increase in total plasma protein.

Composition and energy density of eggs from two species of freshwater turtle with twofold ranges in egg size

Lipid, protein, ash, carbohydrate and water content and energy density of eggs were measured from different clutches over a range of egg size in two species of freshwater turtle. Dry egg contents consisted of protein (54-60%), lipid (25-31%) and ash (5-6%) while carbohydrate was found to be negligible (

Effect of water depth and water velocity upon the surfacing frequency of the bimodally respiring freshwater turtle, Rheodytes leukops

This study examines the effect of increasing water depth and water velocity upon the surfacing behaviour of the bimodally respiring turtle, Rheodytes leukops. Surfacing frequency was recorded for R. leukops at varying water depths (50, 100, 150 cm) and water velocities (5, 15, 30 cm s(-1)) during independent trials to provide an indirect cost-benefit analysis of aquatic versus pulmonary respiration. With increasing water velocity, R. leukops decreased its surfacing frequency twentyfold, thus suggesting a heightened reliance upon aquatic gas exchange. An elevated reliance upon aquatic respiration, which presumably translates into a decreased air-breathing frequency, may be metabolically more efficient for R. leukops compared to the expenditure (i.e. time and energy) associated with air-breathing within fast-flowing riffle zones. Additionally, R. leukops at higher water velocities preferentially selected low-velocity microhabitats, presumably to avoid the metabolic expenditure associated with high water flow. Alternatively, increasing water depth had no effect upon the surfacing frequency of R. leukops, suggesting little to no change in the respiratory partitioning of the species across treatment settings. Routinely long dives (>90 min) recorded for R. leukops indicate a high reliance upon aquatic O-2 uptake regardless of water depth. Moreover, metabolic and temporal costs attributed to pulmonary gas exchange within a pool-like environment were likely minimal for R. leukops, irrespective of water depth.

Lesions caused by cardiovascular flukes (Digenea : Spirorchidae) in stranded green turtles (Chelonia mydas)

Evidence of infection with spirorchid flukes (Digenea: Spirorchidae) was sought at necropsy of 96 stranded green turtles, Chelonia mydas, that were examined during the course of a survey of marine turtle mortality in southeastern Queensland, Australia. Three species of spirorchid (Hapalotrema mehrai, H. postorchis, and Neospirorchis schistosomatoides) were identified. Severe disease due to spirorchid fluke infection (spirorchidiasis) was implicated as the principal cause of mortality in 10 turtles (10%), and appeared to be one of multiple severe problems in an additional 29 turtles (30%). Although flukes were observed in only 45% of stranded C. mydas in this study, presumed spirorchid fluke infection was diagnosed in an additional 53% of turtles, based principally on characteristic necropsy lesions and to a lesser extent on the histopathological detection of spirorchid eggs. Characteristic necropsy lesions included miliary spirorchid egg granulomas, which were observed most readily on serosal surfaces, particularly of the small intestine. Cardiovascular lesions included mural endocarditis, arteritis, and thrombosis, frequently accompanied by aneurysm formation. Resolution of thrombi was observed to occur via a combination of granuloma formation about indigestible components (spirorchid fluke egg shells) and exteriorization through the vessel wall, which resulted in granulomatous nodules on the adventitial surface. Septic aortic thrombosis complicated by disseminated bacterial infection, observed in five turtles, was recorded for the first time. Egg granulomas were ubiquitous in turtle tissues throughout this study. Although they generally appeared to be mild or incidental lesions, they were occasionally associated with severe multifocal granulomatous pneumonia or meningitis.

Glossocercus chelodinae (MacCallum, 1921) n. comb. (Cestoda : Dilepididae) from freshwater turtles in Australia and a redefinition of the genus Bancroftiella Johnston, 1911

Glossocercus chelodinae (MacCallum, 1921) n. comb. is redescribed from fresh material recovered from the intestine of an Australian freshwater turtle, Chelodina expansa. G. chelodinae can be distinguished from all other species of the genus by the shape of its rostellar hooks. it is suggested that this species has colonised fish-eating turtles from fish-eating birds. The morphological relationships among Parvitaenia, Bancroftiella and Glossocercus are discussed. The diagnosis of Bancroftiella is amended and marsupials are eliminated as hosts. Bancroftiella sudarikovi Spasskii & Yurpalova, 1970 becomes a synonym of Glossocercus glandularis (Fuhrmann, 1905); only B. tennis Johnston, 1911, the type-species, and B. ardeae Johnston, 1911 remain in the genus.

Notopronocephalus peekayi gen. et sp. n. (Digenea: Pronocephalidae) from Australian freshwater turtles

Notopronocephalus peekayi gen, et sp, n. is described from the intestine of Elseya latisternum Gray, 1867, E. dentata (Gray, 1863) and Emydura signata Ahl, 1932 from rivers in Queensland. The new genus is distinguished by the absence of ventral glands, simple (neither diverticulate nor sinuous) caeca terminating at the anterior margin of the testes, excretory arms not uniting in forebody, single ovary, two opposite testes close to the posterior end of the body, intracaecal genital pore, vitelline follicles anterior to the testes, cirrus-sac orientated obliquely and not divided into two portions, and the uterus intracaecal. This is the first pronocephalid to be described from an Australian freshwater turtle and the first from the family Chelidae.

Conservation and economic benefits of wildlife-based marine tourism: Sea turtles and whales as case studies

Tourism development can have positive and/or negative impacts on wildlife. However, if tourism is developed in accordance with the basic tenets of wildlife tourism such an activity can be sustainable and can aid the conservation of species. Based on two case studies in Queensland, Australia, this article outlines the various economic and conservation benefits arising from wildlife-based tourism. Some of the benefits are direct, such as tangible economic benefits, others are less tangible, such as increased visitors’ willingness to pay in principle for the conservation of species. Wildlife-based tourism is shown to foster political support for the conservation of species utilized for such tourism by various mechanisms. Non-consumptive uses of wildlife are not only sustainable, but may provide a viable alternative to consumptive uses.