Antechinomys Research Articles

On the composition of

Morphological and molecular studies have consistently suggested that Sminthopsis, as currently defined, is rendered paraphyletic by the kultarr (Antechinomys laniger). They have also suggested a sister relationship between the kultarr and the long-tailed dunnart. Based on DNA sequence data from multiple mitochondrial and nuclear gene loci we reassign the long-tailed dunnart (formerly Sminthopsis longicaudata) to Antechinomys. Although there is good evidence of genetic structure within the kultarr (A. laniger), it does not correspond to the two currently recognised subspecies, viz A. laniger laniger and A. l. spenceri. We conclude that Antechinomys consists of two species, A. laniger and A. longicaudatus, consistent with morphology. We suggest that the observed genetic and morphological variation within A. laniger merits a more thorough investigation of more samples from across its range to resolve the taxonomy.

Hearing thresholds of small native Australian mammals – red-tailed phascogale (Phascogale calura), kultarr (Antechinomys laniger) and spinifex hopping-mouse (Notomys alexis)

Abstract Hearing is essential for communication, to locate prey and to avoid predators. We addressed the paucity of information regarding hearing in Australian native mammals by specifically assessing the hearing range and sensitivity of the red-tailed phascogale (Phascogale calura), the kultarr (Antechinomys laniger) and the spinifex hopping-mouse (Notomys alexis). Auditory brainstem response (ABR) audiograms were used to estimate hearing thresholds within the range of 1–84 kHz, over a dynamic range of 0–80 dB sound pressure level (SPL). Phascogales had a hearing range of 1–40 kHz, kultarrs 1–35 kHz and hopping-mice 1–35 kHz, with a dynamic range of 17–59 dB SPL, 20–80 dB SPL and 30–73 dB SPL, respectively. Hearing for all species was most sensitive at 8 kHz. Age showed no influence on optimal hearing, but younger animals had more diverse optimal hearing frequencies. There was a relationship between males and their optimal hearing frequency, and greater interaural distances of individual males may be related to optimal hearing frequency. Because nocturnal animals use high-range hearing for prey or predator detection, our study suggests this may also be the case for the species examined in this study. Future studies should investigate their vocalizations and behaviour in their natural environments, and by exposing them to different auditory stimuli.

Identification of the mRNA encoding interleukin-6 and its receptor, interleukin-6 receptor α, in five marsupial species

Expressed coding sequences for interleukin-6 (IL-6) and interleukin-6 receptor α (IL-6R) were examined in five marsupial species. Full length expressed coding sequences for IL-6 and IL-6R were identified and characterized in the gray short-tailed opossum (Monodelphis domestica). For IL-6, ∼225 bp fragments of the mRNA sequence were identified in the red-tailed phascogale (Phascogale calura), kultarr (Antechinomys laniger), and stripe-faced dunnart (Sminthopsis macroura), while ∼563 bp fragments of mRNA encoding IL-6R were identified in the red-tailed phascogale, kultarr, stripe-face dunnart and fat-tailed dunnart (Sminthopsis crassicaudata). Relative expression levels of IL-6 and IL-6R were examined in the heart, muscle, lung, liver, spleen and kidney of adult red-tailed phascogales, and IL-6 gene expression was found to be significantly higher in the lung and spleen than the other tissues examined, while the expression of IL-6R was significantly higher in the liver, lung and spleen. These results now serve as a reference point for examining the role and levels of IL-6 and IL-6R in the health and disease of these marsupial species. The pro-tumorigenic nature of IL-6 is of particular interest, and the identification of these IL-6 and IL-6R coding sequences provides a platform for further work to evaluate the potential role of IL-6 in marsupial cancers.

To bask or not to bask: Behavioural thermoregulation in two species of dasyurid, Phascogale calura and Antechinomys laniger

Torpor is an important physiological process used to reduce body temperature and thus energy needs in mammals and birds. Rewarming from torpor can be costly. In some small mammals basking is used to reduce the cost of rewarming from torpor. The use and duration of basking was measured in two native Australian marsupials, the red-tailed phascogale (Phascogale calura) and kultarr (Antechinomys laniger), using a heat rock. Animals were observed via video cameras to determine whether they used basking behaviours and whether this behaviour was affected by food availability. Both species became accustomed to the heat rock as time progressed. Absence of food increased basking duration and frequency in some individuals but not all animals. Generally kultarrs basked for longer periods than phascogales, and kultarrs would bask at all hours of the day while phascogales showed a strict nocturnal regime (1900–0700h). The results demonstrate that basking may be an important behavioural adaptation of the kultarr; while the phascogale requires further research.

Biology, life history, and captive management of the kultarr (Antechinomys laniger)

The kultarr (Antechinomys laniger) is a small marsupial that inhabits arid and semi-arid areas of central Australia. The kultarr is the only species within its genus and is morphologically unique from other dasyurids. Like many Australian marsupials, the kultarr has undergone significant population declines and although it is listed as "least concern" on the IUCN red list little is known of their ecology in the wild. A lack of knowledge on their biology can be attributed to their cryptic nature and sparse population densities. Recent studies of kultarrs have increased knowledge of the biology and captive management, with current data predominately coming from captive colonies. Captive studies of the kultarr have provided data on reproduction, diet choice, nutrition, health, and disease. Kultarrs are polyestrous seasonal breeders and are believed to be mostly insectivorous. Diseases noted in captive individuals provide some insight into those that may influence animals in the wild. Further research is required on both wild and captive populations to increase the knowledge base and determine appropriate management techniques for both wild and captive populations.

Using climate variables to predict small mammal occurrence in hot, dry environments

Many species are considered to be threatened by the direct and synergistic effects of increased temperatures and less reliable rainfall caused by anthropogenic climate change. The climate of arid Australia is naturally defined by high temperatures and highly variable rainfall. In these environments the survival of small mammals is facilitated by a range of physiological, morphological and behavioural adaptive traits (e.g. insectivorous diets, torpor, nocturnal activity and sheltering in burrows). Features within the landscape associated with these traits may have a proximal influence on species occurrence and be critical for predicting the distribution of arid species. Here we explored the contribution of coarse- and fine-scale environmental variables, sampled from 150 to 10,000 m from known species records, to the development of more robust species distribution models. The inclusion of environmental variables representing topography, soil and vegetation better modelled occurrence for all five small mammal species (up to 55.2 % DE increase over climate-only models) and increased discrimination of species occurrence in an out-of-sample cross-validation for Antechinomys laniger, Dasyuroides byrnei and Notomys cervinus (e.g. increase in area-under-the curve by 0.4). For these species, model performance (% DE) increased with the resolution of environmental data used, reflecting a coarse-scale relationship with distance to watercourse (e.g. at 1,000 m), but masking a fine-scale relationship with rainfall during winter (at 150 m). The inclusion of a fine-scale variable shrub cover under 0.5 m (SD) improved the representation of S. macroura occurrence. These results show improved representation of habitats and resources using course- and fine-scale variables, which may be vital to model the occurrence of some species and their refuge habitats, but as static variables may limit accurate predictions of the effect of climate change on species range dynamics.

Description of the gastrointestinal tract and associated organs of the kultarr (Antechinomys laniger)

This paper provides a macro- and microscopic description of the digestive tract of the kultarr (Antechinomys laniger), a small dasyurid marsupial. The digestive tract was simple, with no external differentiation between the small and large intestine, and lacked a caecum. Mean gross length of the kultarr digestive tract was 165.2 ± 32.1 mm. Microscopically, the tissues had cell types similar to those of other mammals. The new information will aid future post-mortem investigations of captive kultarrs and future studies of nutrition.

Rate of passage through the digestive tract of the kultarr (Antechinomys laniger)

The kultarr (Antechinomys laniger) is a small insectivorous marsupial that has undergone significant declines in geographical range. Limited studies have been undertaken on kultarr biology and therefore there is a lack of understanding of its basic biological and ecological requirements. Rate of passage in the kultarr, determined using mealworm cuticle as a marker in minced beef, was 1.6 ± 0.2 h and mean retention time was 3.9 ± 1.2 h. The rapid transit time was consistent for an animal of equivalent body mass, dietary preference and gastrointestinal tract morphology. Mean retention time was short, similar to that of other mammals with a small body mass. This study provides the first insight into gastrointestinal physiology of the little known kultarr.

Digestibility of feeding regimes of the red-tailed phascogale (Phascogale calura) and the kultarr (Antechinomys laniger) in captivity

Digestibility was studied in the red-tailed phascogale (Phascogale calura) and the kultarr (Antechinomys laniger), small insectivorous/carnivorous marsupials, to determine their nutrient requirements in captivity. The marsupials were fed a range of insects, rat (Rattus rattus) and small carnivore food (Wombaroo). Digestibility experiments were conducted for a total of 12 days, which incorporated a five-day adjustment phase followed by a seven-day collection period. The apparent digestibility values for the phascogale and kultarr were above 81% for dry matter, energy, protein and lipids on all diets provided. No significant difference was found between phascogales and kultarrs on the same diet with respect to apparent digestibility of dry matter, energy, protein and lipids. The apparent absorption of minerals varied for each diet for the phascogale and kultarr. Maintenance energy requirements were determined to be 954 kJ kg0.75 day–1 for the red-tailed phascogale and 695 kJ kg0.75 day–1 for the kultarr. Presented here are the most comprehensive data on diet digestibility for dasyurids thus far.

Observation of reproductive strategies of captive kultarrs (Antechinomys laniger)

Captive kultarrs (Antechinomys laniger) were bred from June to February. Their gestation period was longer than 12 days, as suggested by previous research. Pouches were observed to determine whether births occurred. Individuals were capable of producing offspring in their second and third year of life, which has been suspected previously, but never demonstrated in other published studies.

Reproduction in Antechinomys laniger ('spenceri' Form) ( Marsupialia : Dasyuridae): Field and Laboratory

Antechinomys laniger is polyoestrous, and animals from Sandringham Station in south-western Queensland are in breeding condition from midwinter to midsummer. Laboratory observations suggest that photoperiod may be the proximate factor controlling the timing of the breeding season. Females enter oestrus up to six times during the season, and as the season progresses the length of the oestrous cycle decreases. The estimated length of gestation is 12 days or less. Females may rear up to six young. The young are weaned when about 3 months old and become sexually mature at 11.5 months. Both males and females are potentially capable of breeding in more than one season. Higher than average rainfall may have led to a decline in the numbers of A. laniger on Sandringham Station.

Ecology of Highly Venomous Snakes: The Australian Genus Oxyuranus (Elapidae)

The taipan, Oxyuranus scutellatus, is a large slender elapid of coastal tropical Aus- tralia. The small-scaled snake, 0. microlepidotus, is a similar snake from the arid zone. These are among the most highly venomous snakes in Australia, and probably in the world. We present information on body sizes, sexual size dimorphism, feeding habits, reproductive cycles, fecundity and inferred growth rates, based on dissection of museum specimens and observation of captive snakes. Adult snakes average approximately 1.5 m SVL in both Oxyuranus species, and males and females attain similar body sizes. Oxyuranus species are unique among Australian elapids in feeding exclu- sively upon endothermic prey. A wide variety of marsupials and rodents is taken: especially Rattus villosissimus and Antechinomys laniger by 0. microlepidotus, and Melomys sp., Mus musculus, Perameles nasuta and Rattus spp. by 0. scutellatus. The large body size, highly toxic venom and snap and release bite of Oxyuranus species may be adaptations to feeding on mammalian prey. Over recent decades, taipans have become more common relative to other large elapid species: we suggest that this may be due to the introduction of the toxic cane toad (Bufo marinus) as well as habitat modification by agriculture. Both Oxyuranus species are oviparous, with mating and oviposition from August to December. Fecundity (7-20 eggs), incubation period (60-80 days), and size at hatching (300-340 mm SVL) are similar in both species. Captive taipans show rapid growth, with sexual maturation as early as 16 months of age in males, and 28 months in females. In several aspects of morphology, ecology and behavior, 0. scutellatus is strongly convergent with an African elapid, Dendroaspis polylepis (the black mamba).