Notomys Alexis Research Articles

Conservation implications of a new fossil species of hopping-mouse, Notomys magnus sp. nov. (Rodentia: Muridae), from the Broken River Region, northeastern Queensland

The Australian hopping-mouse Notomys includes 10 species, eight of which are considered extinct, vulnerable, near-threatened or endangered. Here we report a new fossil species from the Broken River Region, northeastern Queensland. Notomys magnus sp. nov. is represented by craniodental material from late Quaternary cave deposits. It was a relatively large-bodied species of Notomys with a mass estimated to be ca 83 g. Notomys magnus sp. nov. is immediately distinguishable from the spinifex hopping-mouse (Notomys alexis), the northern hopping-mouse (Notomys aquilo), the fawn hopping-mouse (Notomys cervinus), the dusky hopping-mouse (Notomys fuscus), Mitchell’s hopping-mouse (Notomys mitchellii) and the big-eared hopping-mouse (Notomys macrotis) by its larger size (especially its longer upper molar crown length). Notomys magnus sp. nov. differs from the large-bodied Darling Downs hopping-mouse (Notomys mordax), long-tailed hopping-mouse (Notomys longicaudatus), short-tailed hopping-mouse (Notomys amplus) and broad-cheeked hopping-mouse (Notomys robustus) by possessing a unique first upper molar (M1) morphology including relatively well-developed buccal cusps, cusp T1 prominently isolated from T4, a relatively narrow posterior loph and an incipient anterior accessory cusp. Fossils of N. magnus sp. nov. are found in association with remains of several arid-adapted taxa, including the plains mouse (Pseudomys australis), the northern pig-footed bandicoot (Chaeropus yirratji), and N. longicaudatus, possibly indicating that N. magnus sp. nov. was also arid-adapted. Dating of fossil deposits containing N. magnus sp. nov. demonstrates that it was extant in the mid-Holocene (ca 8.5 ka) so it may have been still extant at the time of European colonization but suffered extinction soon after, mirroring the fate of similarly arid-adapted contemporaneous taxa (Chaeropus yirratji and N. longicaudatus). Historical extinctions in Notomys are biased towards larger species (N. amplus, N. longicaudatus and N. robustus), and the discovery of N. magnus sp. nov. adds further to that list. Given the already high number of extinct and endangered species within Notomys, the discovery of another member that suffered geologically recent extinction has conservation implications for modern critical weight range mammals (including other species of rodents) that are particularly susceptible to extinction. Most historical extinctions of critical weight range mammals were in southern and central Australia, but the discovery of N. magnus sp. nov. suggests that species in the tropical north also were detrimentally affected.Vikram Vakil [vikram.vakil@uqconnect.edu.au], School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia;Jonathan Cramb [jonathan.cramb@qm.qld.gov.au], Queensland Museum, Brisbane, Australia;Gilbert J. Price [g.price1@uq.edu.au], School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia;Gregory E. Webb [g.webb@uq.edu.au], School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland 4072, Australia;Julien Louys [j.louys@griffith.edu.au], Australian Research Centre for Human Evolution, Griffith University, Brisbane, Queensland 4101, Australia.

Validation of an enzyme immunoassay for the non-invasive measurement of faecal androgen metabolites in spinifex hopping mice (Notomys alexis)

Androgens may play a key role in shaping the unique reproductive traits of male spinifex hopping mice (Notomys alexis), but little is known about the reproductive endocrinology of this species. Measurement of faecal androgen metabolites (FAMs) offers a non-invasive tool for monitoring testicular activity. Before applying this tool, physiological validation is required to demonstrate that changes in FAMs reflect changes in circulating testosterone for a given species. The goal of this study was to validate an enzyme immunoassay for monitoring FAMs in Notomys alexis. We compared the performance of two different assays (UVM-T and R156/7) for monitoring changes in FAMs following the administration of human chorionic gonadotropin (hCG) to stimulate androgen production by the testes. Both assays detected a significant increase in FAMs and had similar patterns. The UVM-T assay was more sensitive to changes in testicular activity, with a shorter excretion lag time and greater response magnitude. These findings indicate that we can reliably monitor testicular activity using faecal hormone metabolite analysis in Notomys alexis and can now utilise FAM measurements to better understand the species’ unusual reproductive biology.

A nomadic avian predator displays flexibility in prey choice during episodic outbreaks of rodents in arid Australia.

In environments driven by unpredictable resource pulses, populations of many consumer species experience dramatic fluctuations in abundance and spatial extent. Predator-prey relationships in these acyclic systems are poorly understood in particular with respect to the level of prey specialisation shown by nomadic predators. To understand the dynamics of such a system I examined the response to rodent outbreaks by the letter-winged kite (Elanus scriptus) in the Simpson Desert, Australia; a region that experiences major pulses in primary productivity, driven by unpredictable rainfall events. The kite feeds on small mammals and is the only night-hunting species in the Accipitridae. Letter-winged kites irrupted in the area on only three occasions during 20years of sampling (1999-2019) and remained for a maximum of 20months. Each period of kite occupation occurred only during the increase and/or peak phase of rodent population cycles (which occurred three times during the study). During each period kite diet was dominated by small (10-50g body mass) quadrupedal rodents (Pseudomys australis, P. hermannsburgensis, Mus musculus). Abundance of these species varied across the three outbreaks and kites typically captured them in proportion to availability. The large body mass (134g) long-haired rat (Rattus villosissimus) was abundant during one outbreak but was infrequently consumed. The bipedal spinifex hopping-mouse (Notomys alexis) was within the kites' favoured prey size range (35g) but was consistently avoided. The flexibility in prey selection by letter-winged kites appears to be an important adaptation for survival and reproduction by species exploiting acyclic rodent outbreaks.

Female reproductive suppression in an Australian arid zone rodent, the spinifex hopping mouse

AbstractThe spinifex hopping mouse (Notomys alexis) is an Australian arid zone rodent that undergoes boom and bust population cycles in its natural environment. Most populations studied to date have been sympatric with exotic predators and introduced herbivores, likely affecting their population dynamics. Therefore, it is unclear whether high‐density populations of hopping mice are regulated by purely extrinsic factors or whether intrinsic factors are also at play. We hypothesized that reproductive suppression of female N. alexis may occur in high‐density populations as has been observed in some other rodent species. Reproductive condition of adult female N. alexis was compared between a high‐density population within the Arid Recovery reserve, where exotic predators and introduced herbivores are excluded, and a low‐density population on adjacent pastoral properties (no exclusions). Trap success was 10 times higher inside the reserve than at pastoral sites, and no adult females were observed breeding in the reserve population, despite 26 % of females at pastoral sites recorded breeding. Our results indicate that adult female N. alexis in the high‐density reserve population were reproductively suppressed, but the similar sex ratios in both populations and the high female body mass and body condition in the reserve indicated that this was not due to demographic differences between the two populations or food scarcity. Our study indicates that the ‘busts’ observed in arid zone rodent populations may be amplified due to the presence of exotic predators and/or grazing by introduced herbivores. We contend that prior to the introduction of exotic predators and introduced herbivores in Australia, the arid zone rodent N. alexis would likely have been more abundant and intrinsic population regulation through female reproductive suppression may have played a larger role in population regulation.

Morphological diversity of the spermatozoon and male reproductive tract in Australian Hopping mice, genus Notomys – is it determined by sexual selection?

AbstractHopping mice (Genus Notomys) are a monophyletic group of Australian Old Endemic murid rodents in the Tribe Hydromyini four of which, Notomys alexis, N. mitchellii, N. fuscus and N cervinus, occur in arid or semiarid environments. Here, we compare the size and morphology of their testes, spermatozoa, accessory sex glands and external genitalia across the species, and from these data, we draw conclusions as to their likely breeding systems. We show that both wild caught and laboratory bred adult N. alexis, N. fuscus and N. mitchellii individuals have extremely small testes, but their spermatozoa vary in morphology across the species. The ventral prostate is the only large accessory sex gland present, and their glans penis has very large spines. By contrast N. cervinus individuals have significantly larger testes with their spermatozoa being less variable but generally more complex in morphology, their seminal vesicles and coagulating glands are much larger, whereas the glans penis has only small spines. Since these reproductive traits in N. cervinus are more similar to those of most other hydromyine rodents in the genus Pseudomys, they are likely to reflect the retention of the ancestral condition within the Notomys lineage whereas the divergent reproductive traits of the other species of tiny testes, variable sperm, small seminal vesicles and coagulating glands and large penile spines are probably more recently derived traits. It is suggested that N. cervinus with its relatively larger testes mass and greater abundance of sperm of more consistent morphology has retained a mating system that may potentially involve some intermale sperm competition whereas, by contrast, the reproductive anatomy of the other three Notomys species suggests that these species exhibit monogamy.

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.

What can we deduce about the reproductive condition of spinifex hopping mice (Notomys alexis) from external examination?

Field studies often use external examination of the vagina or the swelling of the scrotum to make deductions about the reproductive condition of rodents. In this study we sought to determine what information on reproductive condition could be gained from external examination of the reproductive anatomy of spinifex hopping mice (Notomys alexis) using individuals from a captive colony. Female N. alexis with perforate vaginae had a significantly larger mean uterine mass and larger mean maximum ovarian follicle diameter than non-perforate females. Corpora lutea were recorded in two perforate animals but were not present in females with a ‘pinhole’-size perforate or non-perforate vagina. In male hopping mice scrotal bulge size was unrelated to testes mass, ventral prostate mass or presence/absence of sperm in the cauda epididymides. Males with dark scrotal pigmentation had a significantly smaller mean testes mass than males with light or no pigmentation. However, there was no relationship between scrotal pigmentation and ventral prostate mass or sperm presence in the cauda epididymides. Our study suggests that vaginal perforation is an acceptable indicator of sexual maturity in female hopping mice, but scrotal bulge size and scrotal pigmentation should not be used to predict reproductive condition of males.

Go with your gut: Digestibility and digestive function of two arid-zone Australian murids, Pseudomys australis and Notomys alexis

Spinifex hopping-mice (Notomys alexis) and plains mice (Pseudomys australis) are able to successfully occupy arid zones of Australia. We studied the digestive parameters and energy assimilation of captive spinifex hopping-mice and plains mice. The experiment consisted of six diets fed to the animals for periods of 12days per food type. On a dry matter basis, the plains mice consumed between 2.5 and 7.2% and the hopping-mice between 5.8 and 9.3% of their body mass in food per day. The body mass of the spinifex hopping-mice increased significantly on the sunflower seed diet, while body mass did not change significantly for the plains mice on any diet. Apparent digestibility of macronutrients was similar in the hopping-mice and plains mice when maintained on the same diet, however digestibility of total micronutrients differed. Maintenance energy requirements for the plains mice were 529kJkg−0.75d−1 and spinifex hopping-mice 550kJkg−0.75d−1. Spinifex hopping-mice and plains mice are able to exploit a range of food items and efficiently digest macronutrients, to ensure they meet their nutritional needs, an ability they require in the variable arid environment. The information gained in this study increases the paucity of information on Australian native murids, specifically their digestive function and energy requirements, and will aid captive murid management. The study will allow future expansion into field studies, to aid the conservation of wild rodent diets and nutrition of arid zone murids.

Gamete cryopreservation of Australian 'old endemic' rodents – spermatozoa from the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis)

Most of the Australian ‘old endemic’ rodents have greatly reduced distributions with several species now threatened with extinction. Application of assisted reproductive technology has the potential to assist in their conservation programs in at least a few species. Here we describe an attempt to cryopreserve spermatozoa from two of these species – those of the plains mouse (Pseudomys australis) and spinifex hopping mouse (Notomys alexis), which have dramatic differences in sperm morphology. Slow and rapid freezing and three different cryoprotectant media with either raffinose, glycerol and/or skim milk were used and the results compared with those of house mouse sperm, which were used as controls. Sperm morphology, motility, membrane integrity and DNA damage were determined. Prior to cryopreservation there was a higher percentage of morphologically normal, motile, P. australis sperm than in those from N. alexis. Following cryopreservation, regardless of treatment, the percentage of motile sperm was low but it was higher when raffinose with skim milk was used as a cryoprotectant than in raffinose with glycerol albeit that minimal differences in membrane integrity or DNA damage were evident. Raffinose with skim milk should thus be used as a cryoprotectant for storing sperm of these Australian rodents in the future.

Three new species of the sucking louse genus Hoplopleura (Phthiraptera:Anoplura: Hoplopleuridae) from rodents (Mammalia: Rodentia: Muridae) in northern Australia.

Three new species of the rodent louse genus Hoplopleura (Anoplura: Hoplopleuridae) are described and illustrated from Australia: H. melomydis new species from Melomys burtoni (Muridae: Hydromyini, grassland melomys) and M. capensis (Muridae: Hydromyini, Cape York melomys) from Queensland; H. notomydis new species and H. setosa new species from Notomys alexis (Muridae: Hydromyini, spinifex hopping mouse) from the Northern Territory. These new louse species are the first lice recorded from each of the three host rodent species.

Dead mouse hopping: Tyzzer’s disease in spinifex hopping-mice (Notomys alexis)

Tyzzer’s disease is caused by Clostridium piliformes and affects a wide range of domestic and wildlife species. Non-descript signs, if any, and a short incubation period make Tyzzer’s disease difficult to diagnose and treat before death occurs. Here we describe an unexpected outbreak of Tyzzer’s disease in a colony of native Australian spinifex hopping-mice (Notomys alexis).In this study captive hopping-mice were used in a nutrition trial (n=11), and others were housed in close proximity (n=4). During the nutrition trial, two hopping-mice exhibited signs of lethargy and diarrhoea, and were removed from the trial but died soon after. Other hopping-mice exhibited limited clinical signs of ill-health, prior to their death. In total four animals were found dead, and another seven were euthanised, to prevent a potential disease outbreak. Tyzzer’s disease was confirmed post-mortem using histopathology silver stain to detect the bacilli-shaped bacteria (C. piliformes) in liver tissue of two hopping-mice. After Tyzzer’s disease was confirmed enhanced infection control measures were implemented. Enhanced control measures included the use of metal containers for food and water, sick animals were fed and cleaned last, 5% sodium hypochlorite was used as the cleaning agent, stricter hand washing protocols and a change of gloves between feeding animals, and strict limits on persons entering the facility.Control measures for this disease should include euthanasia of any animals suspected to be infected, complete disinfection of all enclosures and associated equipment using sodium hypochlorite. Molecular methods could be employed to ensure complete removal of bacterial spores prior to new animals being moved into enclosures where affected animals were housed. Tyzzer’s disease is a fast spreading disease which can cause detrimental effects to captive colonies and their environment. Captive colonies subjected to stress are at risk of Tyzzer’s disease. Appropriate quarantine procedures, close montoring and quick action in response to signs of illness will ensure Tyzzer’s disease outbreaks do not occur.

Changes in abundance and reproductive activity of small arid-zone murid rodents on an active cattle station in central Australia

Context Boom and bust population cycles are characteristic of many arid-zone rodents, but it is unknown to what extent these dynamics might be influenced by the presence of invasive rodents, such as the house mouse (Mus musculus) in Australia. Aim To determine whether the presence of M. musculus can have negative consequences on the population abundance and reproduction of two old Australian endemic rodents (the spinifex hopping mouse, Notomys alexis, and sandy inland mouse, Pseudomys hermannsburgensis). Methods The study took place on the sand dunes of a cattle station in central Australia. Population abundance was estimated as the number of individuals caught in small mammal traps, and female reproductive condition by external examination and, in a few cases, euthanasia and inspection of the reproductive tract. Key results Two synchronous periods of high abundance of N. alexis and M. musculus occurred several months after significant rainfall events, whereas the abundance of P. hermannsburgensis was consistently low. No reproduction took place in N. alexis or M. musculus when populations had reached high abundance. During low-rainfall periods, M. musculus was not detected on the sand dunes, and the two endemic species were sparsely distributed, with reproduction occasionally being evident. Conclusions During dry periods, M. musculus contracted back to refuges around the homestead and, after significant rainfall, it expanded onto the sand dunes and became abundant at the same time as did N. alexis. In contrast, and unlike in areas where M. musculus was generally rare, P. hermannsburgensis always remained at a low abundance. These patterns suggest that in areas of the natural environment close to human-modified sites, populations of at least one species of an old endemic rodent are supressed by the presence of M. musculus. Reproduction did not occur in the old endemics at times of high M. musculus abundance, but did take place in spring/early summer, even in some dry years. Implications The spread of M. musculus into the Australian arid zone may have had negative impacts on the population dynamics of P. hermannsburgensis. These findings suggest that the presence of human settlements has resulted in refuges for house mice, which periodically spread out into the natural environment during ‘boom’ times and adversely affect the natural population cycle of ecologically similar species such as P. hermannsburgensis.

Greater bilby burrows: important structures for a range of species in an arid environment

Greater bilbies (Macrotis lagotis) have been described as ecosystem engineers and their burrows are significant structures across an often featureless and harsh arid landscape. Remote cameras were deployed at bilby burrows to determine whether bilby burrows were important structures for other species. Cameras detected two mammal species, brush-tailed mulgara (Dasycercus blythi) and spinifex hopping mice (Notomys alexis), permanently occupying bilby burrows, and a further two species, short-beaked echidnas (Tachyglossus aculeatus acanthion) and sand goannas (Varanus gouldii), regularly using bilby burrows for shelter. An additional suite of 16 mammal, bird, reptile, amphibian and invertebrate species were detected interacting with bilby burrows. There was no difference in the number of species using disused or occupied bilby burrows, indicating that even disused bilby burrows are important structures for other species. We show that bilby burrows are used by a range of species and are analogous to the traditional, mostly North American, and commonly provided text book examples of the gopher tortoise and kangaroo rat. The disappearance of bilbies across at least 80% of their former range and thus the disappearance of their burrows as important structural resources in a harsh, arid environment may have had important consequences for a range of species.

The role of leptin and ghrelin in appetite regulation in the Australian Spinifex hopping mouse, Notomys alexis, during long-term water deprivation

Water deprivation of the Spinifex hopping mouse, Notomys alexis, induced a biphasic pattern of food intake with an initial hypophagia that was followed by an increased, and then sustained food intake. The mice lost approximately 20% of their body mass and there was a loss of white adipose tissue. Stomach ghrelin mRNA was significantly higher at day 2 of water deprivation but then returned to the same levels as water-replete (day 0) mice for the duration of the experiment. Plasma ghrelin was unaffected by water deprivation except at day 10 where it was significantly increased. Plasma leptin levels decreased at day 2 and day 5 of water deprivation, and then increased significantly by the end of the water deprivation period. Water deprivation caused a significant decrease in skeletal muscle leptin mRNA expression at days 2 and 5, but then it returned to day 0 levels by day 29. In the hypothalamus, water deprivation caused a significant up-regulation in both ghrelin and neuropeptide Y mRNA expression, respectively. In contrast, hypothalamic GHSR1a mRNA expression was significantly down-regulated. A significant increase in LepRb mRNA expression was observed at days 17 and 29 of water deprivation. This study demonstrated that the sustained food intake in N. alexis during water deprivation was uncoupled from peripheral appetite-regulating signals, and that the hypothalamus appears to play an important role in regulating food intake; this may contribute to the maintenance of fluid balance in the absence of free water.

The role of refuges in the persistence of Australian dryland mammals.

Irruptive population dynamics are characteristic of a wide range of fauna in the world's arid (dryland) regions. Recent evidence indicates that regional persistence of irruptive species, particularly small mammals, during the extensive dry periods of unpredictable length that occur between resource pulses in drylands occurs as a result of the presence of refuge habitats or refuge patches into which populations contract during dry (bust) periods. These small dry-period populations act as a source of animals when recolonisation of the surrounding habitat occurs during and after subsequent resource pulses (booms). The refuges used by irruptive dryland fauna differ in temporal and spatial scale from the refugia to which species contract in response to changing climate. Refuges of dryland fauna operate over timescales of months and years, whereas refugia operate on timescales of millennia over which evolutionary divergence may occur. Protection and management of refuge patches and refuge habitats should be a priority for the conservation of dryland-dwelling fauna. This urgency is driven by recognition that disturbance to refuges can lead to the extinction of local populations and, if disturbance is widespread, entire species. Despite the apparent significance of dryland refuges for conservation management, these sites remain poorly understood ecologically. Here, we synthesise available information on the refuges of dryland-dwelling fauna, using Australian mammals as a case study to provide focus, and document a research agenda for increasing this knowledge base. We develop a typology of refuges that recognises two main types of refuge: fixed and shifting. We outline a suite of models of fixed refuges on the basis of stability in occupancy between and within successive bust phases of population cycles. To illustrate the breadth of refuge types we provide case studies of refuge use in three species of dryland mammal: plains mouse (Pseudomys australis), central rock-rat (Zyzomys pedunculatus), and spinifex hopping-mouse (Notomys alexis). We suggest that future research should focus on understanding the species-specific nature of refuge use and the spatial ecology of refuges with a focus on connectivity and potential metapopulation dynamics. Assessing refuge quality and understanding the threats to high-quality refuge patches and habitat should also be a priority. To facilitate this understanding we develop a three-step methodology for determining species-specific refuge location and habitat attributes. This review is necessarily focussed on dryland mammals in continental Australia where most refuge-based research has been undertaken. The applicability of the refuge concept and the importance of refuges for dryland fauna conservation elsewhere in the world should be investigated. We predict that refuge-using mammals will be widespread particularly among dryland areas with unpredictable rainfall patterns.

Streptobacillus notomytis sp. nov., isolated from a spinifex hopping mouse (Notomys alexis Thomas, 1922), and emended description of Streptobacillus Levaditi et al. 1925, Eisenberg et al. 2015 emend.

A pleomorphic, Gram-negative, rod-shaped, indole-, oxidase- and catalase-negative, non-spore-forming, non-motile bacterium was isolated in 1979 from the heart of a spinifex hopping mouse (Notomys alexis Thomas, 1922) with septicaemia and stored as Streptobacillus moniliformis in the strain collection of the Animal Health Laboratory, South Perth, Western Australia (AHL 370-1), as well as under CCUG 12425. On the basis of 16SrRNA gene sequence analyses, the strain was assigned to the genus Streptobacillus, with 99.4 % sequence similarity to the type strain of Streptobacillus moniliformis, 95.6 %sequence similarity to the type strain of Streptobacillus hongkongensis and 99.0 %sequence similarity to the type strain of Streptobacillus felis. The clear differentiation of strain AHL 370-1T from Streptobacillus moniliformis, Streptobacillus hongkongensis and Streptobacillus felis was also supported by rpoB, groEL and recA nucleotide and amino acid sequence analysis. Average nucleotide identity was 87.16 % between strain AHL 370-1T and Streptobacillus moniliformis DSM 12112T. Physiological data confirmed the allocation of strain AHL 370-1T to the family Leptotrichiaceae, considering the very similar profiles of enzyme activities and fatty acids compared to closely related species. Within the genus Streptobacillus,isolate AHL 370-1T could also be separated unambiguously from the type strains of Streptobacillus moniliformis, Streptobacillus hongkongensis and Streptobacillus felis by MALDI-TOF mass spectrometry. Two further strains (KWG2 and KWG24) isolated from asymptomatic black rats in Japan were highly similar to AHL 370-1T. On the basis of these data, we propose the novel species Streptobacillus notomytis sp. nov., with the type strain AHL370-1T (=CCUG 12425T=DSM 100026T=CCM 8593T=EF 12425T).

A case of melanoma in a native Australian murid, the spinifex hopping-mouse (Notomys alexis)

Generally the reporting of diseases and parasites in Australian native murids is rare despite murids making up ~25% of the native mammal fauna of Australia. This paper reports a malignant melanoma in a captive spinifex hopping-mouse (Notomys alexis) and is the first case of melanoma reported in any native Australian murid. With no exposure to ultraviolet radiation the melanoma is proposed to be the result of genetic predisposition and age. As no other reports have been observed in the colony it is likely to be a very rare event in captivity and unlikely to occur in the wild.

Risky Business: Do Native Rodents Use Habitat and Odor Cues to Manage Predation Risk in Australian Deserts?

In open, arid environments with limited shelter there may be strong selection on small prey species to develop behaviors that facilitate predator avoidance. Here, we predicted that rodents should avoid predator odor and open habitats to reduce their probability of encounter with potential predators, and tested our predictions using a native Australian desert rodent, the spinifex hopping-mouse (Notomys alexis). We tested the foraging and movement responses of N. alexis to non-native predator (fox and cat) odor, in sheltered and open macro- and microhabitats. Rodents did not respond to predator odor, perhaps reflecting the inconsistent selection pressure that is imposed on prey species in the desert environment due to the transience of predator-presence. However, they foraged primarily in the open and moved preferentially across open sand. The results suggest that N. alexis relies on escape rather than avoidance behavior when managing predation risk, with its bipedal movement probably allowing it to exploit open environments most effectively.

Coevolution of the male and female reproductive tracts in an old endemic murine rodent of Australia

AbstractThe male reproductive tract of most Australian hopping mice in the genus Notomys has a suite of highly derived features that differ markedly from those of other Australian rodents. These include, among others, extremely small testes, a reduced complement of accessory sex glands and a spiny penis. Here we ask the question – what are the coevolved features of the female reproductive tract? To answer this question, we used histology and resin casts to compare the reproductive tract of the Australian plains mouse (Pseudomys australis) with that of the Spinifex hopping mouse (Notomys alexis). In P. australis, the cervix is highly fibrous and has two small canals whereas the vagina has prominent fornices, a large lumen and a folded epithelial lining. By contrast, in N. alexis the cervix is not prominent and is far more cellular. It has a very small, single lumen with the boundary between it and the vagina not being readily evident. The vagina has minute fornices and is surrounded by a comparatively thick muscle coat. Shortly after ejaculation, N. alexis had many uterine sperm that associated with coagulated material but, unlike in P.australis, no large vaginal plug occurs after ejaculation. These observations support the conclusion that N. alexis has a highly derived distal region of the female reproductive tract which has coevolved with that of the male. It appears to facilitate rapid sperm transport postcoitum without the need for a large copulatory plug.

Appetite regulation in desert‐adapted Spinifex hopping mice during water deprivation

Spinifex hopping mice, Notomys alexis, can maintain water balance without drinking. This study examined the appetite control system in hopping mice during water deprivation (WD) at five time points (2, 5, 10, 17, and 29 days) using leptin and ghrelin ELISA, and Real Time qPCR and western analysis of leptin, leptin receptor, ghrelin, ghrelin receptor, and NPY. We found that water‐deprived hopping mice showed a cyclical food intake in which hypophagia is followed by sustained food intake that is greater than water‐replete animals. The mice lost body weight primarily due to fat loss but then weight stabilised and increased as WD is prolonged (29 days). Plasma leptin decreased in parallel with fat loss but then increased again, which is probably due to leptin expression in tissues such as skeletal muscle. WD had no effect on central leptin receptor mRNA and protein. Plasma ghrelin decreased during the hypophagia but then increased significantly as food intake increased; it then decreased markedly despite a sustained food intake during the longer WD time points. As WD was prolonged, brain ghrelin mRNA expression was up‐regulated but the receptor mRNA was down‐regulated. Finally, brain NPY mRNA was up‐regulated during WD. In conclusion, central control of appetite is probably critical in hopping mice for sustaining food intake to provide substrate to generate metabolic water when free water is unavailable.