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In a number of marsupial species, females exhibit characteristic, stereotyped parturient behavior that facilitates the passage of the neonates to the pouch. In macropodids, this parturient behavior can be induced in non-pregnant females and males by treatment with either prostaglandin F2alpha (PGF2alpha) or oxytocin (OT). This study investigated the effects of PGF2alpha and OT on behavior of Tasmanian devils. Animals tended to sit or lie down quickly, with little vocalization, after treatment with PGF2alpha or OT, while after saline, the animals remained alert, seldom sat, and frequently vocalized. Hormone treatment caused increased respiration. Urogenital and pouch grooming, a characteristic element of parturient behavior in macropodids, was seen in only one devil after hormone treatment. However, no pouch or urogenital grooming was seen in videotape of a devil giving birth, so this may not be a feature of parturient behavior in this species. Overall behavior of males and females was very similar suggesting that the behavioral effects observed may be due to direct neural action of PGF2alpha or OT, rather than an indirect response to uterine or vaginal contractions caused by the hormones. This study is the first to demonstrate that OT results in PGF2alpha secretion as PGFM levels rose after OT injection.

The Tasmanian bettong (Bettongia gaimardi, a marsupial) is a rat-kangaroo that increases nonshivering thermogenesis (NST) in response to norepinephrine (NE). This study attempted to assess whether brown adipose tissue (BAT), a specialized thermogenic effector, is involved in NST in the bettong. Regulatory NST, indicated by resting oxygen consumption (Vo2) of the whole body, was measured under conscious conditions at 20 degrees C with various stimuli: cold (4 degrees -5 degrees C) or warm (25 degrees C) acclimation, NE injection, and the beta3-adrenoceptor agonist (BRL) 37344. In line with the functional studies in vivo, the presence of BAT was evaluated by examining the expression of the uncoupling protein 1 (UCP1) with both rat cDNA and oligonucleotide probes. Both NE and BRL 37344 significantly stimulated NST in the bettong. After cold acclimation of the animals (at 4 degrees -5 degrees C for 2 wk), the resting Vo2 was increased by 15% and the thermogenic effect of NE was enhanced; warm-acclimated animals showed a slightly depressed response. However, no expression of UCP1 was detected in bettongs either before or after cold exposure (2 wk). These data suggest that the observed NST in the marsupial bettong is not attributable to BAT.

The Tasmanian pademelon, Thylogale billardierii, is a medium-sized wallaby that adapts well to captivity and, unlike the well-studied tammar wallaby, is capable of breeding all year round. It may, therefore, be a useful model species for research into the reproductive biology of macropod marsupials. This paper presents necessary background data on histological changes in the reproductive organs and the rate of embryonic growth during gestation in T1 billardierii. After Day 4 RPY (removal of young from the pouch) the gravid and non-gravid uteri differ significantly in some histological parameters. The corpus luteum becomes active by Day 6 RPY and is fully developed by Day 14 RPY; it begins to degenerate from Day 19 RPY. Plasma progesterone concentrations through gestation follow a pattern similar to that in the tammar wallaby. There is an early, smaller, peak at Day 5 RPY, with plasma concentrations of progesterone then falling until the larger pre-partum peak occurs several days before birth.

Marsupials at birth are ectothermic and gradually attain the ability to change their metabolic heat production during pouch life. How this process occurs in the bettong has been measured on 13 pouch young from week 1 until 3 weeks after pouch vacation (week 18). Oxygen consumption was measured at 35 degrees C (pouch temperature) and at 22 degrees C. The results at 35 degrees C showed an increase in metabolic rate from week 1 until week 12 when there was a decrease to near adult levels after pouch vacation. At 22 degrees C young bettongs had a lower metabolic rate (compared with measurements made at 35 degrees C) until week 9 after which there was an increase above measurements made at 35 degrees C. Noradrenaline had little effect until week 10 after which the metabolic rate (although measured at 35 degrees C) paralleled the levels measured at 22 degrees C. The free thyroxine level was low in early pouch life, increased to a peak at week 12 then decreased. Thermal conductance increased until week 10 after which it decreased, reaching values similar to those of adult bettongs by week 20. The results indicate that non-shivering thermogenesis occurs in this macropodoid marsupial. This phenomenon may be a phylogenetic difference between macropodid and non-macropodid marsupials as also suggested by Nicol et al. (1997).

Bettongs give birth on the night that their large pouch young finally vacates the pouch. We have hypothesized that hormones associated with this birth are also involved in pouch vacation. Injections of prostaglandin F2 alpha (PGF2 alpha) caused contractions of the pouch. In a separate experiment PGF2 alpha caused pouch vacation; oxytocin had a similar effect but with a longer latency. In addition both hormones induced birth behavior in adult and immature females as well as in males. When a prostaglandin synthesis inhibitor (Finadyne) was given first, oxytocin failed to produce birth behavior or pouch vacation. This finding leads us to suggest that oxytocin exerts its behavioral effects via prostaglandin synthesis. These experiments are the first to demonstrate an effect by oxytocin on reproductive behavior in a marsupial.

The Tasmanian bettong (Bettongia gaimardi) is a small rat kangaroo without detectable brown adipose tissue (BAT). In view of our previous findings of norepinephrine-mediated increase in O2 consumption (Vo2) in the perfused hindlimb of this species, the present study examined the effect of alpha-adrenoceptors on the thermogenesis of conscious bettongs at rest by infusing adrenergic agents via an indwelling catheter in the tail vein. The resting Vo2 was 22.9 +/- 1.9 mmol.kg-1.h-1. Norepinephrine (10-80 micrograms.kg-1.min-1) stimulated Vo2 in a dose-dependent manner with the maximal increment of 46.7%. Naphazoline (an alpha 1,alpha 2-adrenergic agonist) and phenylephrine (an alpha 1-adrenergic agonist) also elicited increases in Vo2 with maximal values of 29.6 and 34.8%, respectively. In contrast, the alpha 2-adrenergic agonist clonidine had no significant effects. Both alpha- and beta-adrenergic blockers were used to antagonize the submaximal increase in Vo2 elicited by norepinephrine. As a dose of 10 micrograms.kg-1.min-1, the alpha-adrenergic blocker phentolamine abolished the effects of naphazoline and phenylephrine and reduced norepinephrine-induced Vo2 by 45.5%. The beta-adrenergic blocker propranolol inhibited the norepinephrine-induced Vo2 by 58.8% at 20 micrograms.kg-1.min-1. A combination of the two antagonists blocked 82.5% of the norepinephrine-induced Vo2. Pretreatment of the animal with indomethacin (1 mg/kg), a known inhibitor of prostaglandin cyclooxygenase, had no effect on phenylephrine-elicited Vo2. Taken together, these results indicate that alpha 1-adrenoceptors are directly involved in norepinephrine-induced thermogenesis in non-BAT tissue(s).

Many macropodids exhibit lactational quiescence during which an embryo produced at post-partum mating is retained as a blastocyst in utero while a pouch young is sucking. The sucking stimulus maintains secretion of prolactin which may in some species inhibit the activity of the corpus luteum and, hence, the development of the embryo. When the sucking frequency decreases, the blastocyst resumes development. In the present study, the dopamine agonist bromocriptine, which in many mammals results in decreased secretion of prolactin from the pituitary gland, was administered to the Tasmanian bettong (Bettongia gaimardi) at two different doses (12.5 mg kg(-1) and 5 mg kg(-1)). Although lactation was affected by both doses, as evidenced by slower growth of the pouch young or their loss, in only two cases did the quiescent blastocyst activate at the time of injection. This occurred with the highest dose of bromocriptine and was reflected by earlier changes in plasma progesterone concentrations. It is concluded that the Tasmanian bettong is unusual in its lack of sensitivity to bromocriptine.

Basal body temperature, quantitative changes in vaginal smears and plasma concentrations of progesterone were measured during a number of oestrous cycles in Tasmanian bettongs (Bettongia gaimardi). These methods of monitoring the reproductive cycle were compared in an attempt to find a technique that allowed non-stressful assessment of the reproductive condition of the bettongs. Telemetric measurement of basal body temperature showed that there was a diurnal variation of 1.3 degrees C, typical of a nocturnal animal. During the oestrous cycle, there was a small, but not significant, peak in basal body temperature at oestrus (day 0) followed by a significant trough on day 2. There was a significant increase on day 3 and the temperature remained raised until day 10, during which time plasma progesterone concentrations are also high; the temperature then fell 2 days before oestrus. This fall corresponds to a decrease in concentration of plasma progesterone and in the numbers of leucocytes in vaginal smears. Telemetric measurement of body temperature may be useful as a non-stressful method of monitoring the oestrous cycle in bettongs.

An oestrous cycle length of 33 days (N = 4, range 32-34) was obtained for the common womab from a number of parameters including vaginal smears, vaginal biopsies, changes in pouch morphology and behavioral observation. All but one of the successive periods of oestrus occurred during winter. Hourly measurements of body temperature by telemetry showed a rhythm typical of nocturnal species. Superimposed on this diurnal rhythm was another rhythm whoch could be correlated with the oestrous cycle.

The growth cycle of the corpus luteum (CL) of the potoroo is similar to that of other macropodids. During delayed gestation, the post-partum CL remains quiescent until it is reactivated by removal of the sucking pouch young. The CL then undergoes a period of growth, rapid from Day 6 until Day 12, followed by a gradual decline from Day 21 to Day 27. Excision of the CL before Day 6 of pregnancy either inhibited embryonic development or failed to support it. Excision of the CL between 6 and 21 days after removal of pouch young did not prevent embryos developing to full term but interfered with parturition. Excision on Day 25 after removal of pouch young allowed birth but impaired lactation, neonates dying within 2 days. By Day 27, the CL appeared to be no longer essential for embryonic development, birth or neonate survival. It is suggested that the CL of the potoroo is required for a slightly greater proportion of pregnancy than in most larger kangaroos because the birth canal must be prepared before each parturition.

1. Milk composition and energy content was measured in two related marsupials, Bettongia gaimardi and Potorous tridactylus. 2. Although protein content was consistently higher in bettong milk, lactational trends in both species are similar to those reported for other marsupials. 3. The faster relative growth rate of the bettong may be correlated with the increased protein and a higher milk intake.

Milk samples from captive potoroos were analysed for composition during weeks 3-25 of the lactation period. During pouch residence, up to week 16, carbohydrate levels were high, ranging from 9 g 100 ml-1 at week 5 to 15 g 100 ml-1 at week 15; fat levels were consistently low, at around 2 g 100 ml-1; protein levels gradually increased from 5 g 100 ml-1 before week 10 to 12 g 100 ml-1 at week 16. Growth rates during this period increased exponentially, from 1 g week-1 at week 3 to 40 g week-1 at week 16. Thereafter, as the young left the pouch, marked changes were seen in carbohydrate and fat levels: by week 25, carbohydrate levels had fallen to 2 g 100 ml-1, and fat levels had risen to 26 g 100 ml-1. Protein levels increased moderately, reaching 15 g 100 ml-1 by week 25. Growth rates further increased during this period, to reach 60 g week-1 by week 25. Thus, trends in milk composition previously observed in Macropus species were observed also in the potoroo, suggesting a consistent pattern across the macropodid family. Carbohydrate levels in potoroo milk tend to be higher than in other macropodids, but total milk intake is as important as composition in determining growth rates.