Osmoregulation and electrolyte balance in a fully marine mammal, the dugong (Dugong dugon).

Dugongs (Dugong dugon) are fully marine mammals that live independently of fresh water so must balance water and electrolytes in a hyperosmotic environment. To investigate osmoregulation, matched plasma and urine from 51 live wild dugongs were analysed for osmolality, major electrolytes (Na, Cl, K), urea, creatinine, and glucose. Maximum urine osmolality (1468 mOsm kg ) and Na, K, and Cl concentrations (757, 131.

Strategic (adaptive) hypothermia in bull dromedary camels during rut; could it increase reproductive success?

In this study of body temperatures (T(b)) in free ranging dromedary camels, we found that bulls in rut start the days cooler. Daily minima during rut averaged 0.6 degrees C lower than at other times (95% CI 0.

The exceptional longevity of an egg-laying mammal, the short-beaked echidna (Tachyglossus aculeatus) is associated with peroxidation-resistant membrane composition.

The echidna Tachyglossus aculeatus is a monotreme mammal from Australia that is exceptionally long-living. Its documented maximum lifespan of 50 years is 3.7 times that predicted from its body mass.

Respiratory properties of blood in flatback turtles (Natator depressus).

Oxygen equilibrium curves and other respiratory-related variables were determined on blood from the flatback turtle (Natator depressus) and, for comparison, on some samples from the loggerhead turtle (Caretta caretta). The oxygen carrying capacity of the flatback turtle, 4.9-8.

Respiration by buried echidnas Tachyglossus aculeatus.

Short-beaked echidnas have an impressive ability to submerge completely into soil or sand and remain there, cryptic, for long periods. This poses questions about how they manage their respiration, cut off from a free flow of gases. We measured the gradient in oxygen partial pressure (PO2) away from the snouts of buried echidnas and oxygen consumption (VO2) in five individuals under similar conditions, in two substrates with different air-filled porosities (fa).

Temperature and the respiratory properties of whole blood in two reptiles, Pogona barbata and Emydura signata.

We investigated the capacity of two reptiles, an agamid lizard Pogona barbata and a chelid turtle Emydura signata, to compensate for the effects of temperature by making changes in their whole blood respiratory properties. This was accomplished by measuring the P50 (at 10, 20 and 30 degrees C), hematocrit (Hct), haemoglobin concentration ([Hb]) and mean cell haemoglobin concentration (MCHC) in field acclimatised and laboratory acclimated individuals. The acute effect of temperature on P50 in P.

The evolution of endothermy and its diversity in mammals and birds.

Many elements of mammalian and avian thermoregulatory mechanisms are present in reptiles, and the changes involved in the transition to endothermy are more quantitative than qualitative. Drawing on our experience with reptiles and echidnas, we comment on that transition and on current theories about how it occurred. The theories divide into two categories, depending on whether selection pressures operated directly or indirectly on mechanisms producing heat.

Body temperature in captive long-beaked echidnas (Zaglossus bartoni).

The routine occurrence of both short-term (daily) and long-term torpor (hibernation) in short-beaked echidnas, but not platypus, raises questions about the third monotreme genus, New Guinea's Zaglossus. We measured body temperatures (T(b)) with implanted data loggers over three and a half years in two captive Zaglossus bartoni at Taronga Zoo, Sydney. The modal T(b) of both long-beaks was 31 degrees C, similar to non-hibernating short-beaked echidnas, Tachyglossus aculeatus, in the wild (30-32 degrees C) and to platypus (32 degrees C), suggesting that this is characteristic of normothermic monotremes.