Human migration is important in the international spread of exotic Salmonella serovars in animal and human populations.

The exposure of indigenous humans and native fauna in Australia and the Wallacea zoogeographical region of Indonesia to exotic Salmonella serovars commenced during the colonial period and has accelerated with urbanization and international travel. In this study, the distribution and prevalence of exotic Salmonella serovars are mapped to assess the extent to which introduced infections are invading native wildlife in areas of high natural biodiversity under threat from expanding human activity. The major exotic Salmonella serovars, Bovismorbificans, Derby, Javiana, Newport, Panama, Saintpaul and Typhimurium, isolated from wildlife on populated coastal islands in southern temperate areas of Western Australia, were mostly absent from reptiles and native mammals in less populated tropical areas of the state. They were also not recorded on the uninhabited Mitchell Plateau or islands of the Bonaparte Archipelago, adjacent to south-eastern Indonesia. Exotic serovars were, however, isolated in wildlife on 14/17 islands sampled in the Wallacea region of Indonesia and several islands off the west coast of Perth. Increases in international tourism, involving islands such as Bali, have resulted in the isolation of a high proportion of exotic serovar infections suggesting that densely populated island resorts in the Asian region are acting as staging posts for the interchange of Salmonella infections between tropical and temperate regions.

Reproduction in the marsupial dibbler, Parantechinus apicalis; differences between island and mainland populations.

Details of the reproductive endocrinology of the dibbler, Parantechinus apicalis, an endangered member of the Family Dasyuridae, are presented from two geographically-separated populations, living either on the mainland or on islands in Jurien Bay, Western Australia. Plasma free cortisol in males measured in the island population during 1998/9 did not differ between the breeding and non-breeding season, but during the March rut in 2000, when males died after breeding, free cortisol levels were significantly raised. Post-mating mortality in dibbler males is facultative, rather than obligatory and the cortisol data implicate the same physiological sequelae described in other dasyurids. In females, a single annual oestrus was recorded during late summer to autumn in both populations with an onset earlier by 12 days in the mainland animals. Faecal steroids excreted as progesterone metabolites (PM) and oestradiol-17ß were measured during the annual oestrous period and showed significantly higher PM concentrations in island animals. Oestradiol, although raised, was not different between the two populations. A profile of PM levels throughout gestation revealed a small peak at the time of ovulation, followed by slowly rising levels to peak 8 days before birth, indicating slow development of the corpora lutea. Using collective data, the presumptive day of ovulation could be identified, allowing the calculation of a presumptive gestation length of 45days in dibblers from mainland populations. This gestation length compares with that of a related species, Pseudantechinus macdonnellensis, reported at 45-55 days. A surprising finding is the significantly shorter gestation period of approximately 38 days in island animals compared with those from the mainland. This and other differences between reproductive parameters of island and mainland populations are discussed in the context of the 'island syndrome'.

Stress in an Island kangaroo? The Barrow Island euro, Macropus robustus isabellinus.

Selected physiological parameters were monitored over a 4-year period in the Barrow Island euro, Macropus robustus isabellinus, in Western Australia in a study of this species' homeostatic capabilities in an extremely arid habitat where individuals are exposed to high environmental temperatures and a lack of free water for much of the year. Evidence was found of a significant change in the animal's milieu intérieur on only one occasion on Barrow Island: in November 1994, following a protracted 8-month drought. Euros had significantly elevated levels of plasma osmolality, cortisol, anti-diuretic hormone (lysine vasopressin - LVP), and a reduced eosinophil count. This suggests that these animals may have been dehydrated, despite the operation of appropriate physiological responses to water deprivation. Lower eosinophil counts also suggest that immune function may have been suppressed as a result of the elevated corticosteroid levels. Comparisons with the mainland sub-species of the euro revealed the presence of a non-generative normocytic hypochromic anaemia in Barrow Island euros that potentially compromises their aerobic capacity. Barrow Island is Australia's most important A Class Reserve, harbouring 8 species of marsupials, 4 of which are now extinct, or virtually so, on the adjacent mainland. This study reveals the remarkable effectiveness of the euro's homeostatic capacities, however, its future conservation depends on ensuring that potential stress due to declining water availability and environmental change is avoided.

Successfully determining the sex of adult Varanus mertensi (Reptilia: Varanidae) using a combination of both hemipenile eversion and the ratio of androgens:estradiol in plasma.

In remote field localities, given limited access to specialized equipment, determining the sex of captured adult varanid lizards before release can be problematic. Determining the sex of the tropical semiaquatic Varanus mertensi, a species with significant tail musculature, is difficult using traditional hand-pressure-induced hemipenile eversion. As an alternative, we propose an extended technique for identifying the sex of adult V. mertensi. We recommend using a combination of the traditional field-based hemipenile eversion technique and a measurement of the ratio of androgens to estradiol in plasma samples taken from field-captured animals.

Adrenocortical function and a field population of a macropodid marsupial (Setonix brachyurus, Quoy and Gaimard).

Concentrations of corticosteroids and aldosterone have been measured in the plasma and related to the maximum cortisol binding capacity, to the concentration of sodium and potassium of the plasma and to the condition of the animals, in a natural population of the quokka (Setonix brachyurus, Quoy & Gaimard) on Rottnest Island, Western Australia. A marked population in one area has been repetitively sampled at approximately 6 week intervals over a period of 2 years. Animals were found to be in significantly better condition during the hot-dry season. Their plasma concentrations of corticosteroids, 1.09 +/- 0.11 (S.E.M.) and 1.47 +/- 0.14 microgram/100 ml and their plasma sodium concentrations, 147 +/- 0.87 and 142 +/- 1.17 mequiv/1, for the hot-dry and cold-wet seasons respectively, were both significantly different (P less than 0.05). Plasma concentrations of aldosterone were 8.40 +/- 0.57 and 7.06 +/- 0.53 ng/100 ml for the hot-dry and cold-wet seasons. The level of aldosterone fell to levels comparable to those found in salt-replete laboratory animals only during the month of July. In the laboratory, salt deprivation resulted in a significant rise in the concentration of plasma aldosterone, 2.33 +/- 0.57 (S.E.M.) ng/100 ml when salt-replete and 16.95 +/- 2.74 ng/100 ml when salt-deprived (P less than 0.001). Total plasma corticosteroid levels were unaffected by changes in the sodium content of the diet. Injections of ACTH at a rate of 2 i.u./kg caused a significant rise in the levels of plasma corticosteroids which were essentially identical in both high- and low-condition animals. Both temperature fell to a significantly lower level in low-condition animals held in cages after injection of ACTH. These results indicate that the seasonal mortality of th quokka on Rottnest Island does not result from any breakdown in adrenal function, despite a substantial decline in the condition of the animals.

Effect of hypothalamic lesions on water metabolism of the toad Bufo marinus.

The rate of cutaneous water uptake after dehydration was significantly depressed in functionally neurohypophysectomized toads (Bufo marinus), which consequently regained weight much more slowly than intact toads when returned to water. Toads bearing hypothalamic lesions were able to develop an antidiuresis when removed from water to a saturated atmosphere, but the antidiuresis was solely glmerular in origin and was established more slowly than in intact animals. The fractional reabsorption of filtrate increased significantly and the relative free water clearance decreased significantly in intact toads after removal from water. These changes in tubular function, which were not seen in lesioned toads, were responsible for the development of a more rapid and effective antidiuresis in intact animals. Injections of iso-osmotic saline, oxytocin (250 mu./100 g) and vasopressin (50 mu./100 g) had no significant effect on rates of cutaneous water uptake in both intact and lesioned toads. Injections of hyperosmotic saline, however, significantly increased rates of water uptake in both groups of toads, but to a much greater extent in the intact animals. Fluid retention arising from a marked antidiuresis occurred after the injection of vasopressin and hyperosmotic saline, and there was some evidence of an antidiuretic effect of oxytocin with the doses used here. These results and their bearing on the question of the functional significance of the neurohypophysis in anuran amphibians are discussed.

Characterization and properties of a progesterone receptor in the uterus of the quokka (Setonix brachyurus).

A progesterone receptor system, with a high specificity for progestins, was detected in the uterine tissue of the marsupial, Setonix brachyurus (quokka), using the synthetic progestin 17 alpha, 21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (R5020). The apparent equilibrium dissociation constant of the ligand binding to the cytosolic component was 2.2 nmol/l, and to the nuclear component 4.8 nmol/l. Significant loss of binding ability of the receptor occurred when cytosol was pretreated with dextran-coated charcoal. All binding studies were performed, therefore, in the presence of endogenous steroid which was demonstrated to affect the dissociation constant but have no effect on the estimation of the concentration of binding sites. Cytosolic binding was increased sixfold by oestradiol-17 beta treatment in vivo, and the translocation of the bound complex into the nucleus was effected by progesterone. It is suggested that the binding component described plays a role in the action of progesterone on the uterine tissue of the quokka.

Difference in concentration of progesterone in plasma between pregnant and non-pregnant quokkas (Setonix brachyurus).

The plasma progesterone concentrations during pregnancy and the oestrous cycle of the quokka were measured daily after each had been initiated by the removal of pouch young. Progesterone levels ranged from 0.6 ng/ml in the early stages of the oestrous cycle to about 2.5 ng/ml at the peak of the luteal phase. There was no significant difference between pregnant and non-pregnant states before the removal of the pouch young nor in the latter half of the cycle. However, the plasma progesterone concentration on days 3--4 after removal of the pouch young was significantly greater in pregnant animals when compared with non-pregnant animals at the same stage and also when compared with the levels before removal of young. This early peak in the concentration of progesterone in peripheral plasma is discussed in relation to the development of the previously dormant blastocyst.

Blood corticosteroids in Australian marsupial and placental mammals and one monotreme.

Peripheral blood corticosteroid levels were determined in nine species of Australian marsupial (Eastern grey kangaroo, black-tailed, Bennett's and pademelon wallabies, quokka, wombat, koala and Western native and tiger cats), one species of monotreme (echidna) and one placental Australian mammal (dingo). Animals were obtained or bled with minimal disturbance and came from areas considered to have adequate sodium content of the vegetation. Aldosterone, corticosterone, cortisol, 11-deoxycorticosterone and 11-deoxycortisol were measured and levels found to be similar to five introduced eutherian species (sheep, cow, dog, fox and man) with the exception of the koala and the wombat. Cortisol was the predominant corticosteroid, except in the koala, which produced corticosterone in relatively the greatest quantity, and the wombat which produced more 11-deoxycortisol. Steroid levels were generally low in the wombat. ACTH administered to the koala changed its pattern of corticosteroid secretion from predominantly corticosterone to cortisol. In the dingo, administration of ACTH caused rises in corticosteroid levels similar to those seen in most other eutherian mammals.

Determination of 18O by prompt nuclear reaction analysis: application for measurement of microsamples.

A method is described for the routine determination of 18O concentrations in microsamples of biological fluids. The method utilizes the prompt nuclear reaction 18O(p, alpha o)15N, and 846-keV protons from a 3-MeV Van de Graaff Accelerator are focused on approximately 2,000-A-thick Ta2O5 targets prepared by anodic oxidation from 50-microliter samples of water distilled from blood or other biological fluids. The broad cross section of the resonance peak for this nuclear reaction (47 keV) ensures high yields, especially at small reaction angles, and the high-energy alpha particles produced by the reaction (4 MeV) are readily separated from scattered protons by the use of an aluminized Mylar foil of suitable thickness. Background levels of 18O (0.204 atom%) can be detected with run times of approximately 5-8 min, and the sensitivity of the method is of the order of 0.05 atom %. Experimental error due to sample preparation was found to be 1.7%, and counting errors were close to theoretical limits so that total error was of the order of 2.5%. Duplicate samples were analyzed by use of the 18O(p, alpha o)15N reaction at Lucas Heights, Australia, and the 18O(p,n)18F reaction by the method of Wood et al. (Anal. Chem. 47: 646-650, 1975) at the University of California, Los Angeles, and the agreement was excellent (y = 1.0123x - 0.0123, r = 0.991, P less than 0.001). The theoretical limitations and the general applicability of the method in biological studies designed to estimate the rate of metabolism of free-ranging animals are discussed.

Measurement of the rate of protein turnover and synthesis in the marsupial Honey possum (Tarsipes rostratus).

Rates of protein turnover and synthesis were measured in wild-caught Honey possums (Tarsipes rostratus) in the southwest of Western Australia and compared between males and females with and without pouch young. Possums were injected with 50 microg of (15)N-glycine and ammonia collected within 24 h was used as the nitrogen end-product in a single-injection protocol. The overall mean rate of protein synthesis measured was 7.7+/-0.5 g kg(-0.75) day(-1), which falls within the range of values reported for other marsupial species. Whole body rates of nitrogen flux and protein synthesis did not vary significantly between males and females with and without young, but females with pouch young showed significantly lower rates of protein synthesis when expressed in relation to metabolic body size. This difference was no longer apparent, however, if the mass of the females was corrected for the estimated mass of the young in the pouch averaging 9.3+/-1.6 g kg(-0.75) day(-1) and suggesting that the young should not be considered as part of the metabolic body pool. Whole body rates of protein degradation were significantly reduced in females carrying pouch young, suggesting that protein may be being diverted from the pool to milk production. Calculations indicate that the daily fraction of the female's nitrogen synthesis rate that needs to be diverted to pouch young to sustain their growth is less than 5%, and may not be detectable with the current methodology.

Salmonella infections in Antarctic fauna and island populations of wildlife exposed to human activities in coastal areas of Australia.

Salmonella infections in Antarctic wildlife were first reported in 1970 and in a search for evidence linking isolations with exposure to human activities, a comparison was made of serovars reported from marine fauna in the Antarctic region from 1982-2004 with those from marine mammals in the Northern hemisphere. This revealed that 10 (83%) Salmonella enterica serovars isolated from Antarctic penguins and seals were classifiable in high-frequency (HF) quotients for serovars prevalent in humans and domesticated animals. In Australia, 16 (90%) HF serovars were isolated from marine birds and mammals compared with 12 (86%) HF serovars reported from marine mammals in the Northern hemisphere. In Western Australia, HF serovars from marine species were also recorded in humans, livestock, mussels, effluents and island populations of wildlife in urban coastal areas. Low-frequency S. enterica serovars were rarely detected in humans and not detected in seagulls or marine species. The isolation of S. Enteritidis phage type 4 (PT4), PT8 and PT23 strains from Adélie penguins and a diversity of HF serovars reported from marine fauna in the Antarctic region and coastal areas of Australia, signal the possibility of transient serovars and endemic Salmonella strains recycling back to humans from southern latitudes in marine foodstuffs and feed ingredients.

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

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.

Reproduction and embryonic diapause in a marsupial: insights from captive female Honey possums, Tarsipes rostratus (Tarsipedidae).

The reproductive physiology of the polyoestrous Honey possum (Tarsipes rostratus) is virtually unknown except that it shares with the kangaroos and wallabies the phenomenon of embryonic diapause. Its tiny size necessitates an alternate approach to study their reproductive cycle. We have accordingly utilised faecal steroid analysis. Baseline faecal cortisol levels in the Honey possum, at 4.1+/-0.3 mug g-1, are approximately 100-fold those of other mammals and are associated with adrenal glands that, on a mass-specific basis, are almost 10 times larger than the adrenals of other mammalian, including marsupial, species. Histological examination of the adrenal glands revealed no abnormalities, however, but their hypertrophy and the peaks recorded in faecal levels following disturbance suggest that the Honey possum is vulnerable to chronic stressors in the captive situation. Mean faecal progestagens (124.4+/-107.3 ng g-1) and oestradiol-17beta (4.1+/-1.1 ng g-1) in 4 non-pregnant females maintained long term were not different from those of 5 pregnant females (101.4+/-61.0 ng g-1 and 4.3+/-1.5 ng g-1, respectively) and, on analysis, revealed a cyclicity of 24+/-1.2 days. We would predict from this evidence that the gestation period, in the absence of lactation, is approximately 23 days. Four of the pregnant females, monitored from July to November under conditions of 10:14 L:D photoperiod, showed a fall in levels of progestagens from 175.9+/-10.8 ng g-1 in July and August to 30.9+/-9.4 ng g-1 in October, while mean faecal levels of oestradiol-17beta increased from 3.8+/-0.4 ng g-1 in July to 5.7+/-0.3 ng g-1 in October. September and October are months of peak reproductive activity in the wild and we suggest that these hormonal modulations may represent an entrained reproductive rhythm. Blastocysts appear to develop at varying rates, both within the one uterus, and between the two uteri of a single female. In addition, the time taken to reach the blastocyst stage may be longer than in any other marsupial studied to date. An association of the age of the pouch young with the stage reached by the developing blastocyst does not support the conclusion that blastocysts, once formed, grow slowly during lactation or diapause. Contrary to previous reports, we have documented what appears to be a lactational inhibition on blastocysts in diapause and have estimated the length of the 'delayed' reproductive cycle in two females as less than 2 weeks. Reactivation of blastocysts in Tarsipes has been shown to be stimulated by shortening day lengths after the summer solstice, a response similar to the annual breeding period of macropodid marsupials. Results from studying Honey possums in captive conditions suggest that the control of diapause in Tarsipes appears to be three-fold; lactational, photoperiodic and an entrained rhythm.

Kidney function and the role of arginine vasotocin in three agamid lizards from habitats of differing aridity in Western Australia.

Western Australian agamid lizards are diverse and inhabit mesic to very arid areas of the state. Although reptilian kidneys are unable to elaborate hyperosmotic urine, we hypothesised that the renal system of lizards inhabiting arid areas would display an enhanced ability to conserve water under the control of the antidiuretic peptide hormone, arginine vasotocin (AVT). To examine this, the renal physiological and endocrine responses to osmotic challenge in three closely-related Australian agamid lizards inhabiting arid, semi-arid, and mesic environments were studied. The species studied were Pogona minor (mesic), Ctenophorus salinarum (semi-arid), and Ctenophorus nuchalis (arid). Circulating AVT was assayed and renal variables such as glomerular filtration rate (GFR), urine flow rate (V), and fractional reabsorption of filtrate FRH2O were measured in response to hypernatraemia, water load, and dehydration. Hypernatraemia and dehydration induced antidiuresis in all three species through similar mechanisms involving both glomerular and tubular responses. However, in salt-loaded P. minor the response was largely glomerular in nature, as FRH2O did not increase relative to the hydrated condition. The magnitude of the antidiuretic response was also greater in P. minor, indicating a greater sensitivity to osmotic challenge. Plasma concentrations of AVT were significantly correlated with FRH2O in P. minor (r2=0.38, P=0.025), but with GFR in C. nuchalis (r2=0.16, P=0.041). We found that the control and mechanisms of renal function among these lizards were largely similar, and there was little support for the hypothesis that arid lizards possess physiological adaptations not present in closely-related mesic lizards. Yet, differences remain in their response to hypernatraemia which may reflect the aridity of their different environments, or their varying habits.

Estradiol-17 beta secretion by the newly formed corpus luteum of a macropodid marsupial, the quokka (Setonix brachyurus).

The production of significant amounts of estradiol-17 beta from the 2-day-old corpus luteum of the macropodid marsupial, Setonix brachyurus (quokka), was shown using an in vitro perifusion system. Sliced corpora lutea and finely chopped extra-luteal ovarian tissue (cortex plus interstitial tissue) were perifused separately for 2 hr, in tandem for the next hour (with the perifusate from the ovarian tissue directed into the chamber containing the corpora lutea), and separately again for a further 2 hr. Overall production rates of estradiol measured by radioimmunoassay were 1.0 pg (mg hr)-1 from luteal tissue and 0.64 pg (mg hr)-1 from the extra-luteal tissue. Androgen production rates were 0.18 ng (mg hr)-1 and 0.06 ng (mg hr)-1 from luteal and extra-luteal tissues, respectively, and progesterone was produced at a rate of 0.80 ng (mg hr)-1 from luteal tissue and 16.5 pg (mg hr)-1 from extra-luteal tissue. Production rates of all three steroids from the perifused tissue increased significantly when the ovary and corpus luteum were perfused in tandem. The secretion of C19 and C18 steroids from the young corpus luteum suggests that luteinization is not yet complete at this stage in the reproductive cycle of the quokka, and the tissue would be better described as a "postovulatory follicle." This is supported in the literature by the occurrence of mitoses in granulosa cells for 6-7 days after resumption of the delayed cycle. This delayed maturation of the macropodid corpus luteum, which is associated with the secretion of significant quantities of estradiol and only a transient spike of progesterone, is discussed in relation to the longer cycles and gestation periods characteristic of macropodid marsupials.

In vitro uterine contractions in the viviparous lizard Tiliqua rugosa: effects of gestation and steroid pretreatment in vivo.

Uterine contractility was investigated in the viviparous lizard Tiliqua rugosa. Arginine vasotocin (AVT) induces rhythmic contractions in vitro in strips of uterine tissue from ovariectomized female T. rugosa. The strength of these contractions was related to the dosage of AVT and reduced by pretreatment in vivo with both progesterone and estradiol-17 beta. The frequency of spontaneous and AVT-induced contractions was enhanced by estradiol-17 beta pretreatment. The strength of AVT-induced contractions in pregnant females was not significantly different from that recorded in nonpregnant females. Spontaneous rhythmic contractions were present only in pregnant females. Ovariectomy did not affect either spontaneous or AVT-induced contractions in pregnant females. The data indicate that ovarian steroids modulate uterine contractility in T. rugosa. It is suggested that, following a decline in plasma progesterone levels, estrogen may be involved in the onset of parturition.