The effect of restricted feeding on the wheel-running activity rhythms of the predatory marsupial Dasyurus viverrinus

Summary The effects of restricted feeding schedules on the circadian rhythms of wheel-running of Dasyurus viverrinus were examined under a light/dark cycle and in constant darkness (experiment 1) and in constant light (experiment 2). The results of the 2 experiments showed that: (1) in contrast to the light/dark cycle, restricted feeding is only a weak zeitgeber for the wheel-running activity rhythms of D. viverrinus; (2) restricted feeding elicits meal anticipatory activity in D. viverrinus comparable to that elicited by restricted feeding in the rat; (3) transient cycles of the anticipatory activity free-run with a period different to that of the main component of activity for several cycles after the termination of restricted feeding; and (4) activity suggestive of beating between 2 oscillators occurs during restricted feeding and after the termination of restricted feeding. Taken together the latter 3 observations suggest that the activity rhythms of D. viverrinus are controlled by at least 2 separate circadian oscillators.     

Phylogeographical population structure of tiger quolls Dasyurus maculatus (Dasyuridae: Marsupialia), an endangered carnivorous marsupial

Tiger quolls, Dasyurus maculatus, are the largest carnivorous marsupials still extant on the mainland of Australia, and occupy an important ecological niche as top predators and scavengers. Two allopatric subspecies are recognized, D.m. gracilis in north Queensland, and D.m. maculatus in the southeast of the mainland and Tasmania. D.m. gracilis is considered endangered while D.m. maculatus is listed as vulnerable to extinction; both subspecies are still in decline. Phylogeographical subdivision was examined to determine evolutionarily significant units (ESUs) and management units (MUs) among populations of tiger quolls to assist in the conservation of these taxa. Ninety-three tiger quolls from nine representative populations were sampled from throughout the species range. Six nuclear microsatellite loci and the mitochondrial DNA (mtDNA) control region (471 bp) were used to examine ESUs and MUs in this species. We demonstrated that Tasmanian tiger quolls are reciprocally monophyletic to those from the mainland using mtDNA analysis, but D.m. gracilis was not monophyletic with respect to mainland D.m. maculatus. Analysis of microsatellite loci also revealed significant differences between the Tasmanian and mainland tiger quolls, and between D.m. gracilis and mainland D.m. maculatus. These results indicate that Tasmanian and mainland tiger quolls form two distinct evolutionary units but that D.m. gracilis and mainland D.m. maculatus are different MUs within the same ESU. The two marker types used in this study revealed different male and female dispersal patterns and indicate that the most appropriate units for short-term management are local populations. A revised classification and management plan are needed for tiger quolls, particularly in relation to conservation of the Tasmanian and Queensland populations.     

Comparative postnatal ontogeny of the skull in the australidelphian metatherian Dasyurus albopunctatus (Marsupialia: Dasyuromorpha: Dasyuridae)

We describe the cranial ontogeny of an australidelphian marsupial, Dasyurus albopunctatus, using a combination of qualitative and quantitative approaches. We examined in detail qualitative morphological changes of just-weaned individuals as compared to old adults; specifically, changes in 31 morphological structures (e.g., processes, foramina) and 38 changes in cranial joints. We also interpreted growth-invariant structures in terms of their functional relevance. We performed a multivariate allometry analysis based on 14 cranial measurements taken from 31 specimens encompassing the entire postweaning period. Three variables (height of occipital plate, breadth of braincase, and height of mandible) showed the same allometric trends in D. albopunctatus and the three marsupial species studied previously in the same framework (Didelphis albiventris, Lutreolina crassicaudata, and Dromiciops gliroides). In addition, D. albopunctatus shared allometric trends in two variables (length of the upper postcanine row and length of the orbit) with the microbiotheriid D. gliroides. Most of the growth trends observed are interpreted as linked to the predominantly carnivorous dietary habit of adult D. albopunctatus. Because dasyuromorphians are most likely basal to the major Australasian radiation of marsupials, knowledge of ontogenetic changes in D. albopunctatus may shed light on the evolution of ontogeny in the highly diverse Australasian marsupial fauna.     

The ultrastructure of the lung of two newborn marsupial species,the northern native cat,Dasyurus hallucatus,and the brushtail possum,Trichosurus vulpecula

Summary The lungs of newborn northern native cats, Dasyurus hallucatus and newborn brushtail possums, Trichosurus vulpecula were examined by both light and electron microscopy. The native cat has a birth weight of 18 mg after a gestation of about 21 days, whereas the brushtail possum weights 200 mg at birth and has a gestation period of 17.5 days. The lungs of the native cat are two large respiratory sacs, with a respiratory lining of squamous cells and surfactant-secreting cells. The capillaries are located within the connective tissue just below this respiratory epithelium. The visceral covering of the lung is formed by squamous cells. The lungs of the possum are composed of numerous large respiratory sacs which are separated by connective tissue septa in which the capillaries are located. The sacs, as in other species, are lined with squamous cells and surfactant secreting cells. It is proposed that the structure of the lung of the newborn marsupial is related more to the size of the newborn rather than to the length of the gestation period.     

Cross‐species amplification at microsatellite loci in Australian quolls including the description of five new markers from the Chuditch (Dasyurus geoffroii)

The quolls are the largest native predators remaining on mainland Australia. We describe the cross‐species testing of all available microsatellite loci for representative across the entire distribution of quolls, with the additional characterization of five new microsatellite loci from the Chuditch. All primers produced clear and polymorphic amplification patterns containing between nine and 17 alleles and with high levels of diagnostic variability. These highly polymorphic primers make them useful additional tools in planning conservation strategies across related conspecifics, many of which are under threat.