Extensive production of Neospora caninum tissue cysts in a carnivorous marsupial succumbing to experimental neosporosis

Experimental infections of Sminthopsis crassicaudata, the fat-tailed dunnart, a carnivorous marsupial widely distributed throughout the arid and semi-arid zones of Australia, show that this species can act as an intermediate host for Neospora caninum. In contrast to existing models that develop relatively few N. caninum tissue cysts, dunnarts offer a new animal model in which active neosporosis is dominated by tissue cyst production. The results provide evidence for a sylvatic life cycle of N. caninum in Australia between marsupials and wild dogs. It establishes the foundation for an investigation of the impact and costs of neosporosis to wildlife

The Burramys Project: a conservationist's reach should exceed history's grasp, or what is the fossil record for?

The fossil record provides important information about changes in species diversity, distribution, habitat and abundance through time. As we understand more about these changes, it becomes possible to envisage a wider range of options for translocations in a world where sustainability of habitats is under increasing threat. The Critically Endangered alpine/subalpine mountain pygmy-possum, Burramys parvus (Marsupialia, Burramyidae), is threatened by global heating. Using conventional strategies, there would be no viable pathway for stopping this iconic marsupial from becoming extinct. The fossil record, however, has inspired an innovative strategy for saving this species. This lineage has been represented over 25 Myr by a series of species always inhabiting lowland, wet forest palaeocommunities. These fossil deposits have been found in what is now the Tirari Desert, South Australia (24 Ma), savannah woodlands of the Riversleigh World Heritage Area, Queensland (approx. 24-15 Ma) and savannah grasslands of Hamilton, Victoria (approx. 4 Ma). This palaeoecological record has led to the proposal overviewed here to construct a lowland breeding facility with the goal of monitoring the outcome of introducing this possum back into the pre-Quaternary core habitat for the lineage. If this project succeeds, similar approaches could be considered for other climate-change-threatened Australian species such as the southern corroboree frog (Pseudophryne corroboree) and the western swamp tortoise (Pseudemydura umbrina)

Q&A: Marsupials vs Placentals: Why is it beneficial for marsupials to have young in a pouch from a small size, as opposed to having them develop internally as eutherians (placental mammals) do?

This article is written in response to a question from Penelope Hacker, Ashgrove, Queensland, outlined above. McAllan compares and contrasts the pros and cons of both systems. Issues of lactation, times of environmental hardship, and immunological advantages are discussed

Timing of Reproduction in Carnivorous Marsupials

Reproduction in many carnivorous marsupials is seasonal; however the proximal cues for reproduction are known for a minority of species. Species from the genera 'Antechinus and Sminthopsis' appear to rely on photoperiodic change for timing of reproduction, with other environmental factors such as pheromones ('Antechinus') and rainfall ('Sminthopsis') of secondary importance. For most other carnivorous marsupials the proximal cues for reproduction have not been determined, although photoperiod is likely to be the major cue for reproductive timing. Unfortunately, almost nothing is known about reproductive activity for many carnivorous marsupials, especially those from South America, and only further studies can clarify how their reproductive life history is controlled, requiring significant further effort on the part of researchers

Coping with chaos: unpredictable food supplies intensify torpor use in an arid-zone marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata)

The severity, duration and amplitude of extreme weather events are forecast to intensify with current climate trends, over both long (e.g. seasonal) and short (e.g. daily) time-scales. As such, the predictability of food supplies for many small endotherms is likely to become increasingly important. Numerous small mammals and birds combat food shortages using torpor, a controlled reduction in metabolic rate and body temperature that helps lower their daily energy requirements. As such, torpor often has been cited as a key feature allowing some small endotherms to survive highly unpredictable climates, such as tropics or dry deserts, but mensurative demonstrations of this are lacking. We have shown here that when a small desert marsupial, the fat-tailed dunnart (Sminthopsis crassicaudata), is offered unpredictable levels of daily food, they increase frequency of daily torpor and length of bouts compared with animals offered ad libitum food, but this was not found for animals offered a 70% food-restricted diet. Our data suggest that simple food restriction may not be sufficient for evaluating the efficacy of torpor as a strategy for managing unpredictable climates

Photoperiod and the timing of reproduction in 'Antechinus flavipes' (Dasyuridae: Marsupialia)

The effect of an artificial, unchanging photoperiod regime was examined in comparison to a natural photoperiodic regime on the reproductive pattern in 'Antechinus flavipes', a small dasyurid marsupial which in the wild has a short, highly synchronized mating period. Females held under a photoperiod of LD 12:12 showed delayed sexual maturity and only one individual entered oestrus, about 3 weeks after females under natural photoperiod. Oestrus could be induced in the remaining females by increasing the photoperiod by 1 min/day for at least 3–4 weeks. In contrast to the females, males under artificial and natural photoperiod showed a similar pattern of maturity and decline of reproductive condition and senility. Only some aspects of sexual maturity were delayed and others were unsynchronized in males under LD 12:12 regime compared to the males held under the natural photoperiod. Our study suggests that, especially in females, changing photoperiod is important in synchronizing reproductive events in 'A. flavipes'

Daily torpor in a pregnant dunnart ('Sminthopsis macroura' Dasyuridae: Marsupialia)

Mammalian reproduction is an energetically expensive process. In addition to normal energetic costs for maintenance, locomotion and thermoregulation, reproduction requires energy expenditure to acquire and process nutrients, produce milk, and transferring nutrients to growing offspring with the consequent increase in metabolic rate (MR) (Farmer 2003). Torpor in heterothermic mammals, on the other hand, results in an overall reduction of energy expenditure and is characterised by a pronounced fall in body temperature and MR (Geiser and Ruf 1995). For most mammals, these different energetic, and also hormonal, demands appear to require a temporal sequence of reproduction and torpor within the yearly schedule and thus, torpor usually occurs during the non-reproductive season (Goldman et al. 1986; Barnes 1996; Stamper et al. 1998; Mzilikazi and Lovegrove 2002). Not surprisingly then, there is a widely held view that torpor and reproduction in mammals are mutually exclusive processes

Photoperiod as a reproductive cue in the marsupial genus 'Antechinus': ecological and evolutionary consequences

Species in the Australian marsupial genus 'Antechinus' exhibit a short annual mating period which is concluded by the abrupt death of all males. The timing of the annual rut within each of the ten described species varies little from year to year at any given locality, but for some species can differ by up to four months between locations. To determine the influence of photoperiod in regulating the precise interannual synchrony of mating and ovulation, we first investigated populations of each species at over 300 localities throughout their geographical ranges to identify the time of reproduction. We then compared the absolute photoperiod and the rate of change of photoperiod prevailing at the time of reproduction in all population localities. A different, and characteristic, rate of change of photoperiod was correlated strongly with the reproductive timing of four species; there was probably a correlation with reproduction in four more species, but sample sizes were small. For two species, there was no obvious photoperiodic correlation with time of reproduction. There was no evidence that absolute photoperiod or ambient temperature explained the synchrony or narrow timespan of reproduction among any species of Antechinus. Different species-specific ovulatory responses to photoperiod appear to separate the timing of reproduction in sympatric species, with the larger member of species pairs usually breeding first. We suggest that photoperiodic cues (1) allow females to produce young during seasons when food is most reliable and abundant and their energetic demands are maximal; (2) facilitate allochronic isolation between sympatric congeners, and (3) maximize body size differences and hence ecological separation between species

The seasonal physiology of 'Antechinus stuartii': renal and gonadal correlates

'Antechinus stuartii' is a small marsupial that has an unusual life history pattern. It includes a highly synchronised brief mating period occurring at the same time every year within a particular population. Following the mating period all males die from an uncontrolled stress response, which is associated with high plasma concentrations of glucocorticoids and testosterone. Seasonal changes in renal structure and function, and their contributions to male mortality were investigated. Changes in the reproductive tract were also assessed. Following the seasonal study, changes in renal structure and function and reproductive tract were assessed in males given depot injections of either saline, testosterone only, cortisol only or testosterone plus cortisol at doses mimicking those found in the mating period. Glomerular filtration rate (GFR) changed seasonally, with GFR of males lower in July and August, and that of females lower only in the premating period. Plasma sodium and chloride levels were higher, and potassium levels were lower in July and August in both sexes. GFR decreased following testosterone treatment, independent of cortisol. Urinary electrolytes, osmolality, and urea significantly decreased in all cortisol treated animals. Plasma potassium and chloride were affected by the administration of cortisol. ... The present study has demonstrated that there are seasonal changes in renal structure and function in male 'A. stuartii', and these changes were mimicked by the administration of testosterone, with less influence from cortisol administration. The accessory reproductive tract was also sensitive to these hormones. This study demonstrates that the synchronous seasonal changes that occur in 'A. stuartii' are not confined to the reproductive tract, and the changes are governed less by cortisol, than by the sensitivity of 'A. stuartii' males to testosterone

A functional nexus between photoperiod acclimation, torpor expression and somatic fatty acid composition in a heterothermic mammal.

The seasonal changes in thermal physiology and torpor expression of many heterothermic mammals are controlled by photoperiod. As function at low body temperatures during torpor requires changes of tissue lipid composition, we tested for the first time whether and how fatty acids are affected by photoperiod acclimation in hamsters, Phodopus sungorus, a strongly photoperiodic species. We also examined changes in fatty acid composition in relation to those in morphology and thermal biology. Hamsters in short photoperiod had smaller reproductive organs and most had a reduced body mass in comparison to those in long photoperiod. Pelage colour of hamsters under short photoperiod was almost white while that of long photoperiod hamsters was grey-brown and black. Short photoperiod acclimation resulted in regular (28% of days) torpor use, whereas all hamsters in long photoperiod remained normothermic. The composition of total fatty acids differed between acclimation groups for brown adipose tissue (5 of 8 fatty acids), heart muscle (4 of 7 fatty acids) and leg muscle (3 of 11 fatty acids). Importantly, 54% of all fatty acids detected were correlated (r(2) = 0.60 to 0.87) with the minimum surface temperature of individuals, but the responses of tissues differed. While some of the compositional changes of fatty acids were consistent with a 'homeoviscous' response, this was not the case for all, including the sums of saturated and unsaturated fatty acids, which did not differ between acclimation groups. Our data identify a possible nexus between photoperiod acclimation, morphology, reproductive biology, thermal biology and fatty acid composition. They suggest that some of the changes in thermal physiology are linked to the composition of tissue and organ fatty acids