Comparative water metabolism of Barrow Island macropodid marsupials: Hormonal versus behavioural-dependent mechanisms of body water conservation

Abstract

Seasonal variations in rates of water turnover were measured over a 7-year period in four species of macropodid marsupials (Lagorchestes conspicillatus, Bettongia lesueur, Petrogale lateralis and Macropus robustus isabellinus), on Barrow Island off the arid Pilbara coast of Western Australia. These ranged from over 100 mL kg(-0.82) d(-1) in wet seasons to as low as 28.2 mL kg(-0.82) d(-1) in dry seasons in the Spectacled hare wallaby, L. conspicillatus. Plasma osmolality increased significantly in both Barrow Island euros (M. robustus isabellinus) and Spectacled hare wallabies in November 1994, in the driest year yet recorded on the island. In contrast, there was no change in plasma osmolality of the other two species (Black-footed rock wallaby, P. lateralis and Lesueur's burrowing bettong, B. lesueur) that exploit cool and humid thermal refugia such as caves and underground warrens to avoid diurnal temperature extremes. Plasma levels of the marsupial antidiuretic hormone (ADH), lysine vasopressin (LVP), were for the most part below the detectable limit of the assay of 0.41 pg mL(-1) in rock wallabies and bettongs, but reached high levels of 16.7+/-4.6 pg mL(-1) and 20.25+/-5.1 pg mL(-1) in euros and hare wallabies, respectively, in dry seasons. LVP levels were positively correlated with plasma osmolality in both euros and hare wallabies, and negatively correlated with total body water content in euros, supporting its rôle as an antidiuretic hormone in these two species. The study highlights the importance of environmental features, such as caves and underground warrens, which are critical for the long-term survival of endangered species such as the Black-footed rock wallaby and the Lesueur's bettong. These species appear to lack ADH-controlled renal systems for the conservation of body water and are thus dependent on behavioural strategies for the maintenance of fluid homeostasis in arid environments.

Effect of Cadmium Contaminated Diet in Controlling Water Behavior by Meriones shawi

“…In deprived water Meriones we show that water intake was provided from preformed water of food and by metabolic water production as described by Speakman [48] and King and Bradshaw [49]. Our findings are in agreement with previous reports showing that renal concentrating mechanisms are the first line of defense against water depletion [4,12,50]. It is well established that modifications of serum osmolality during depletion are detected via osmoreceptors by magnocellular mainly located in the hypothalamic supraoptic nucleus (SON) and paraventricular nucleus (PVN) in the brain [39,51].…”

“…It appears that water intake and water loss are finely balanced by Meriones shawi. Water intake was provided from preformed water of food and by metabolic water production as described by King and Bradshaw [7]. Water loss was limited by the production of very dry feces.…”

Testing the ability of topoclimatic grids of extreme temperatures to explain the distribution of the endangered brush‐tailed rock‐wallaby (Petrogale penicillata)

“…Other species may not be sensitive to extremes because they are not active or physiologically sensitive in the season or at the time of day when extremes occur. Rock-wallabies fit into these categories to some extent because they use shelters to escape climatic extremes (Bradshaw et al, 2001;King & Bradshaw, 2008;DECC, 2008a), but our results suggest that they still favour warmer locations within the landscape to make this strategy more effective. Other species may use burrowing or nest hollows more effectively to reduce the impacts of climatic extremes.…”

Reduced MHC class II diversity in island compared to mainland populations of the black-footed rock-wallaby (Petrogale lateralis lateralis)

“…The black-footed rock-wallaby (Petrogale lateralis lateralis) inhabits outcrops of weathered and fissured rock in semi-arid and arid regions of Western Australia (Eldridge and Close 1995), which are crucial for shelter during high temperatures to reduce loss of body water (King and Bradshaw 2008), and the species can survive in very small areas of habitat, provided that rock piles exist (Main and Yadav 1971). The black-footed rock-wallaby has declined in the extent of its distribution on the mainland by over 90% since European settlement due to fox predation and land clearing.…”