Macropus Fuliginosus Research Articles

Complete genomic characterisation of two novel poxviruses (WKPV and EKPV) from western and eastern grey kangaroos

Poxviruses have previously been detected in macropods with cutaneous papillomatous lesions, however to date, no comprehensive analysis of a poxvirus from kangaroos has been performed. Here we report the genome sequences of a western grey kangaroo poxvirus (WKPV) and an eastern grey kangaroo poxvirus (EKPV), named for the host species from which they were isolated, western grey (Macropus fuliginosus) and eastern grey (Macropus giganteus) kangaroos. Poxvirus DNA from WKPV and EKPV was isolated and entire coding genome regions determined through Roche GS Junior and Illumina Miseq sequencing, respectively. Viral genomes were assembled using MIRA and SPAdes, and annotations performed using tools available from the Viral Bioinformatics Resource Centre. Histopathology and transmission electron microscopy analysis was also performed on WKPV and its associated lesions.The WKPV and EKPV genomes show 96% identity (nucleotide) to each other and phylogenetic analysis places them on a distinct branch between the established Molluscipoxvirus and Avipoxvirus genera. WKPV and EKPV are 170 kbp and 167 kbp long, containing 165 and 162 putative genes, respectively. Together, their genomes encode up to 47 novel unique hypothetical proteins, and possess virulence proteins including a major histocompatibility complex class II inhibitor, a semaphorin-like protein, a serpin, a 3-β-hydroxysteroid dehydrogenase/δ 5→4 isomerase, and a CD200-like protein. These viruses also encode a large putative protein (WKPV-WA-039 and EKPV-SC-038) with a C-terminal domain that is structurally similar to the C-terminal domain of a cullin, suggestive of a role in the control of host ubiquitination. The relationship of these viruses to members of the Molluscipoxvirus and Avipoxvirus genera is discussed in terms of sequence similarity, gene content and nucleotide composition. A novel genus within subfamily Chordopoxvirinae is proposed to accommodate these two poxvirus species from kangaroos; we suggest the name, Thylacopoxvirus (thylaco-: [Gr.] thylakos meaning sac or pouch).

Merycism in western grey (Macropus fuliginosus) and red kangaroos (Macropus rufus)

Kangaroos regurgitate and re-chew digesta on an occasional basis; the behaviour has been termed ‘merycism’. Merycism is distinct from rumination, as it is non-essential for digestive activity, significantly varies in rhythm and frequency, and causes seeming distress. Triggering mechanisms and potential benefits of this behaviour remain unknown. Although often reported, detailed descriptions of macropod merycism are lacking. We performed a systematic evaluation of a series of anecdotal observations of five western grey (Macropus fuliginosus) and one red kangaroos (Macropus rufus) in a feeding situation on two different diets in captivity. We recorded 14 videos with lucerne pellets and 3 videos with chopped lucerne hay feeding, covering a total of 4h 23min of footage with 23 regurgitation events. A characteristic merycism sequence consisted of retreat from the feeding trough, pumping abdominal contractions, slurping, re-chewing and re-swallowing. Individual kangaroos performed different behavioural features, apparently to support the abdominal contractions including throwing back their head (64±40 (SD) %) or, rarely, pumping movements of the forelimbs. Additionally, instead of keeping digesta within the oral cavity and re-swallowing it, it was sometimes spilled (35±40% of the cases). We confirmed characteristic features of merycism previously reported, including the clear distinction to rumination. We hypothesize that the purpose of merycism is the grinding of not sufficiently chewed food particles that trigger specific contractions of the forestomach beyond voluntary control. The numerically higher frequency of this behaviour during pellet compared to hay feeding could support this hypothesis, as pellets were often gobbled hastily. In accord with observations in the literature, we hypothesize that merycism happens more frequently in captivity, as the type of food, fixed feeding times and limited feeding spots make rapid ingestion of food, possibly without proper mastication (i.e. gobbling), more likely.

Camera trap evidence of red fox (Vulpes vulpes) predation attempts on adult macropods

Camera traps provide a novel and quasicovert method of gathering information on animal behaviour that may otherwise remain undetected without sophisticated and expensive filming equipment. In a rangelands pest management project at Mt Hope in the central west of New South Wales, Australia, we recorded foxes seemingly hunting kangaroos on three occasions. While we did not record direct instances of predation, our observations provide camera trap photographic evidence suggesting that foxes will attempt to tackle mammals above the critical weight range, including large macropod species such as western grey kangaroos.

Femoral bone perfusion through the nutrient foramen during growth and locomotor development of western grey kangaroos (Macropus fuliginosus).

The nutrient artery passes through the nutrient foramen on the shaft of the femur and supplies more than half of the total blood flow to the bone. Assuming that the size of the nutrient foramen correlates with the size of the nutrient artery, an index of blood flow rate (Qi) can be calculated from nutrient foramen dimensions. Interspecific Qi is proportional to locomotor activity levels in adult mammals, birds and reptiles. However, no studies have yet estimated intraspecific Qi to test for the effects of growth and locomotor development on bone blood flow requirements. In this study, we used micro-CT and medical CT scanning to measure femoral dimensions and foramen radius to calculate femoral Qi during the in-pouch and post-pouch life stages of western grey kangaroos (Macropus fuliginosus) weighing 5.7 g to 70.5 kg and representing a 12,350-fold range in body mass. A biphasic scaling relationship between Qi and body mass was observed (breakpoint at ca. 1-5 kg body mass right before permanent pouch exit), with a steep exponent of 0.96±0.09 (95% CI) during the in-pouch life stage and a statistically independent exponent of -0.59±0.90 during the post-pouch life stage. In-pouch joeys showed Qi values that were 50-100 times higher than those of adult diprotodont marsupials of the same body mass, but gradually converged with them as post-pouch adults. Bone modelling during growth appears to be the main determinant of femoral bone blood flow during in-pouch development, whereas bone remodelling for micro-fracture repair due to locomotion gradually becomes the main determinant when kangaroos leave the pouch and become more active.

Behavioural adjustments of wild-caught kangaroos to captivity

It is important to understand how wild-caught animals may respond to captivity, and whether their behaviours in captivity are reflective of their wild counterparts. We observed the behaviour of wild-caught western grey kangaroos (Macropus fuliginosus) and red kangaroos (Osphranter rufus; formerly M. rufus) that were transferred to a large naturally vegetated enclosure. Observations were made on the first day of captivity and again after 7–10 days, and were compared with the behaviour of free-living kangaroos at the same locality and over the same period. We quantified feeding, moving, grooming and non-alert behaviours. Of these, grooming was higher in captive kangaroos than in free-living animals on the first day of captivity only, and was no different to that of wild animal by 7–10 days’ captivity. Such self-directed behaviour may be indicative of heightened distress for kangaroos on the first day of captivity, but it may also be indicative of grooming to eliminate contamination of human smells or debris following capture by darting and recovery. Overall, our findings indicate that after a short period of captivity, wild-caught kangaroos adjust to a novel environment relatively quickly, and animals from each species showed behaviour patterns comparable with free-ranging counterparts within 7–10 days after capture and captivity.

Heterochronic neuromuscular junction development in an Australian marsupial (Macropus fuliginosus)

AbstractThe neuromuscular junction (NMJ) provides a connection between the somatic nervous and muscular systems. The present work documents, for the first time, the mature form of the NMJ in an Australian marsupial, the western gray kangaroo Macropus fuliginosus. Marsupials give birth to highly altricial young and the majority of motor system development thus occurs postnatally. We demonstrate that NMJ formation in the forelimbs of kangaroos precedes that in hindlimbs by several weeks, consistent with evidence of precocial forelimb development from other indices of motor system maturation in marsupials. Forelimb and hindlimb NMJs reach a similar level of development by the end of the first postnatal month, an outcome that results from accelerated hindlimb development in the early postnatal period together with a more unexpected stagnation or even regression of forelimb NMJ maturity over the same period. This study suggests that the pattern of NMJ maturation may be adjusted in forelimb as opposed to hindlimb. Elucidation of the underlying cellular control mechanisms may inform current understanding of NMJ formation, and as such the broader processes involved in synaptic formation.

Subsidized commercial harvesting for cost-effective wildlife management in urban areas: A case study with kangaroo sharpshooting

The management of overabundant urban fauna is a contentious issue worldwide, particularly for populations of white-tailed deer (Odocoileus virginianus) in North America and kangaroos (Macropus spp.) in Australia. To be successful, management programs in such settings must be cost-effective, humane, and publicly acceptable. Here, we describe the management of a fenced, urban population of western grey kangaroos (M. fuliginosus) in southwestern Australia, with an estimated population density of 189 kangaroos/km2. After a period of >12 months of solicited public involvement by key stakeholder groups, a licensed professional shooting team, observing a national code of practice, conducted night-time sharpshooting. Over an 11-month period in 2006–2007, 1,009 kangaroos were shot in 43 shooting nights, a mean (±SE) culling rate of 23 ± 3 kangaroos/night or harvest rate of 12 ± 2 kangaroos/hr. Inspectors under the relevant Western Australian legislation functioned as animal welfare observers to ensure that the methods employed for the culling program met the national code of practice and that all license conditions were met. No accidents or injuries occurred during the program. The program produced 17 kg/kangaroo of harvestable meat and biological samples for several research projects. The operational costs of the project were very low, at AU$36/kangaroo, with payments largely limited to incentives paid to commercial harvesters and management staff monitoring public safety and animal welfare. This case study is an example of a publicly acceptable, cost-effective, humane, and lethal urban wildlife control operation. It demonstrates that public acceptance of a cull of wildlife can be forthcoming with appropriate prior consultation and high professional standards. © 2016 The Wildlife Society.

Field metabolic rate, movement distance, and grazing pressures by western grey kangaroos (Macropus fuliginosus melanops) and Merino sheep (Ovis aries) in semi-arid Australia

Details of the energy (food) requirements of wild herbivores are essential for understanding their role in ecosystems generally, and for evaluating their potential impact on co-occurring domestic herbivores, as in the case for Australia’s largest grazing herbivores, the marsupial kangaroos, which co-exist with domestic livestock, particularly the wool breed Merino sheep. Using the doubly labelled water method we compared the field metabolic rate (FMR) of the western grey kangaroo (Macropus fuliginosus melanops) with that of the merino sheep, grazed sympatrically in a large naturally-vegetated enclosure. We combined our FMR studies with fine-scale GPS-monitoring to reveal important and significant impacts of daily movement patterns on the energetics of western grey kangaroos, but not the sheep. The daily FMR was substantially higher for kangaroos with longer daily movements. These individuals elevated their FMRs relative to predicted basal or minimal metabolic rates (i.e. FMR:BMR) by 4–5 times that expected for mature, non-reproductive mammals. Notably, those kangaroos that exhibited FMR:BMRs typical of mammals generally (around 2–3 times) had daily energy requirements around 6245kJ. This level of energy expenditure was less than one third of that of the domestic sheep (22,799kJd−1). Even when compared on a common body mass of 35kg, the western grey kangaroo energy expenditure was only 0.46 that of the merino sheep. Moreover, for typically-sized mature females kangaroos (25kg), which make the bulk of kangaroo populations, the comparative energy requirement was just 0.31 that of a mature, non-breeding merino ewe.

Mitigating impacts of weeds and kangaroo grazing following prescribed fire in a Banksia woodland

SummaryBanksia woodlands are renowned for their flammability and prescribed fire is increasingly employed to reduce the risk of wildfire and to protect life and property, particularly where these woodlands occur on the urban interface. Prescribed fire is also employed as a tool for protecting biodiversity assets but can have adverse impacts on native plant communities. We investigated changes in species richness and cover in native and introduced flora following autumn prescribed fire in a 700‐hectare Banksia/Tuart (Eucalyptus gomphocephala) woodland that had not burnt for more than 30 years. Effectiveness of management techniques at reducing weed cover and the impacts of grazing by Western Grey Kangaroo (Macropus fuliginosus) postfire were also investigated. Thirty plots were established across a designated burn boundary immediately before a prescribed fire in May 2011, and species richness and cover were measured 3 years after the fire, in spring of 2013. Fencing treatments were established immediately following the fire, and weed management treatments were applied annually in winter over the subsequent 3 years. Our results indicate that autumn prescribed fire can facilitate increases in weed cover, but management techniques can limit the establishment of targeted weeds postfire. Postfire grazing was found to have significant adverse impacts on native species cover and vegetation structure, but it also limited establishment of some serious weeds including Pigface (Carpobrotus edulis). Manipulating herbivores in time and space following prescribed fire could be an important and cost‐effective way of maintaining biodiversity values.

A continent-wide analysis of the shade requirements of red and western grey kangaroos

ABSTRACTForaging time may be constrained by a suite of phenomena including weather, which can restrict a species' activity and energy intake. This is recognized as pivotal for many species whose distributions are known to correlate with climate, including kangaroos, although such impacts are rarely quantified. We explore how differences in shade seeking, a thermoregulatory behavior, of 2 closely-related kangaroo species, Macropus rufus (red kangaroos) and M. fuliginosus (western grey kangaroos), might reflect differences in their distributions across Australia. We observed foraging and shade-seeking behavior in the field and, together with local weather observations, calculated threshold radiant temperatures (based on solar and infrared radiant heat loads) over which the kangaroos retreated to shade. We apply these calculated tolerance thresholds to hourly microclimatic estimates derived from daily-gridded weather data to predict activity constraints across the Australian continent over a 10-year period. M. fuliginosus spent more time than M. rufus in the shade (7.6 ± 0.7 h versus 6.4 ± 0.9 h) and more time foraging (11.8 ± 0.5 h vs. 10.0 ± 0.6 h), although total time resting was equivalent (∼8.2 h). M. rufus tolerated 19°C higher radiant temperatures than M. fuliginosus (89°C versus 70°C radiant temperature). Across Australia, we predicted M. fuliginosus to be more restricted to shade than M. rufus, with higher absolute shade requirements farther north. These results corroborate previous findings that M. rufus is more adept at dealing with heat than M. fuliginosus and indicate that M. rufus is less dependent on shade on a continental scale.

Differences down-under: alcohol-fueled methanogenesis by archaea present in Australian macropodids.

The Australian macropodids (kangaroos and wallabies) possess a distinctive foregut microbiota that contributes to their reduced methane emissions. However, methanogenic archaea are present within the macropodid foregut, although there is scant understanding of these microbes. Here, an isolate taxonomically assigned to the Methanosphaera genus (Methanosphaera sp. WGK6) was recovered from the anterior sacciform forestomach contents of a Western grey kangaroo (Macropus fuliginosus). Like the human gut isolate Methanosphaera stadtmanae DSMZ 3091(T), strain WGK6 is a methylotroph with no capacity for autotrophic growth. In contrast, though with the human isolate, strain WGK6 was found to utilize ethanol to support growth, but principally as a source of reducing power. Both the WGK6 and DSMZ 3091(T) genomes are very similar in terms of their size, synteny and G:C content. However, the WGK6 genome was found to encode contiguous genes encoding putative alcohol and aldehyde dehydrogenases, which are absent from the DSMZ 3091(T) genome. Interestingly, homologs of these genes are present in the genomes for several other members of the Methanobacteriales. In WGK6, these genes are cotranscribed under both growth conditions, and we propose the two genes provide a plausible explanation for the ability of WGK6 to utilize ethanol for methanol reduction to methane. Furthermore, our in vitro studies suggest that ethanol supports a greater cell yield per mol of methane formed compared to hydrogen-dependent growth. Taken together, this expansion in metabolic versatility can explain the persistence of these archaea in the kangaroo foregut, and their abundance in these 'low-methane-emitting' herbivores.

Western grey kangaroos (Macropus fuliginosus) include fauna underpasses in their home range

Context The presence of large mammals on roads poses a serious risk to both the animals and motorists if collisions with vehicles occur. Fencing roads can reduce this risk, and it also limits the landscape-scale movements of animals. By also constructing fauna underpasses it may be possible to avoid collisions with vehicles, while, at the same time, allowing the natural movement of animals across the landscape. Aims We aimed to determine whether western grey kangaroos (Macropus fulignosus) would use fauna underpasses and to determine how this may affect their home range. Methods We used motion-activated infrared cameras to monitor the use of one large 8 × 3 m arched underpass and two 0.9-m-diameter fauna underpasses over 342 days between March 2011 and March 2012. The underpasses were situated between reserves separated by a four-lane fenced highway, with one reserve surrounded by residential properties. At the same time, 20 kangaroos (10 males and 10 females) were radio-tracked to determine the size of their home range and to test whether the animals incorporated the fauna underpasses into their daily movements. Key results The large fauna underpass was used 3116 times by individual kangaroos in groups of up to 21 animals, whereas the two smaller underpasses were used only twice. In total, 14 of the 20 radio-collared kangaroos used the large underpass over the course of the study, but underpass use did not affect home-range size. Kangaroos that did not use the underpass had a significantly higher proportion of their home range on residential properties surrounding one of the reserves than did those kangaroos that used the underpass. Conclusions The use of the underpass did not affect the size of the home range of the kangaroos, but it allowed the kangaroos to access grazing areas that would have been otherwise inaccessible. Fauna underpasses allow the safe passage of kangaroos between isolated remnant vegetation patches and may reduce significantly the risks posed to motorists and kangaroos from collisions. Implications Fencing roads and constructing fauna underpasses is a viable solution to reducing some of the problems of managing large kangaroos in peri-urban areas.

Do body size, diet type or residence time explain habitat use in a vertebrate herbivore community?

Many theories attempt to explain patterns of community organisation among large herbivores. We explored the role of body size, diet type and residence time on habitat use in a community comprising four metatherians (western grey kangaroo, Macropus fuliginosus; eastern grey kangaroo, M. giganteus; red-necked wallaby, Notamacropus rufogriseus; swamp wallaby, Wallabia bicolor) and two eutherians (red deer, Cervus elaphus; European rabbit, Oryctolagus cuniculus) in south-eastern Australia. We used camera traps to estimate habitat occupancy, quantified habitat specialisation using relative entropy, and ran regressions using percentage grass consumed, log(mass) and log(time at site) as predictor variables and relative entropy as the response. If body size influenced habitat use, we predicted smaller species would occupy fewer habitats. If diet type influenced habitat use, we predicted intermediate feeders would use more habitats. If the time that a species had been present at a site predicted community organisation, newer species would use more habitats. None of these theories explained habitat use in our community. Red deer used a narrower range of habitats than expected, perhaps due to the poor suitability of habitats available in the Grampians. While interactions between our hypotheses are likely to be important, the body size model deserves further attention in this community.

Ecological specialisation in habitat selection within a macropodid herbivore guild

Specialist species show stronger resource selection, narrower niches and lower niche overlap than generalist species. We examined ecological specialisation with respect to habitat selection in a macropodid community comprising the western grey kangaroo Macropus fuliginosus, red-necked wallaby M. rufogriseus and swamp wallaby Wallabia bicolor in the Grampians National Park, Victoria, Australia. We used radio tracking to quantify habitat selection. We predicted that because the fitness benefits of generalisation and specialisation differ, there would be a mix of generalised and specialised species in our community. As all three macropodid species show marked sexual dimorphism, we also expected that they would show sex-based specialisation. Finally, because many large herbivores select different habitats for foraging and resting, we predicted that our species would specialise on a subset of their overall selected habitat based on activity period (diurnal or nocturnal). All three species specialised on the available resources to some degree. Western grey kangaroos were specialists, at least during the active period. Niche data for the two wallaby species were harder to interpret so we could not determine their degree of specialisation. Within species, we found no evidence of sex-based specialisation. However, we found clear evidence of specialisation by activity period in western grey kangaroos and red-necked wallabies, but not in swamp wallabies. The strength of behavioural decisions made during the active period in influencing specialisation points to the likelihood that bottom-up processes regulate this community.

Decreasing methane yield with increasing food intake keeps daily methane emissions constant in two foregut fermenting marsupials, the western grey kangaroo and red kangaroo.

Fundamental differences in methane (CH4) production between macropods (kangaroos) and ruminants have been suggested and linked to differences in the composition of the forestomach microbiome. Using six western grey kangaroos (Macropus fuliginosus) and four red kangaroos (Macropus rufus), we measured daily absolute CH4 production in vivo as well as CH4 yield (CH4 per unit of intake of dry matter, gross energy or digestible fibre) by open-circuit respirometry. Two food intake levels were tested using a chopped lucerne hay (alfalfa) diet. Body mass-specific absolute CH4 production resembled values previously reported in wallabies and non-ruminant herbivores such as horses, and did not differ with food intake level, although there was no concomitant proportionate decrease in fibre digestibility with higher food intake. In contrast, CH4 yield decreased with increasing intake, and was intermediate between values reported for ruminants and non-ruminant herbivores. These results correspond to those in ruminants and other non-ruminant species where increased intake (and hence a shorter digesta retention in the gut) leads to a lower CH4 yield. We hypothesize that rather than harbouring a fundamentally different microbiome in their foregut, the microbiome of macropods is in a particular metabolic state more tuned towards growth (i.e. biomass production) rather than CH4 production. This is due to the short digesta retention time in macropods and the known distinct 'digesta washing' in the gut of macropods, where fluids move faster than particles and hence most likely wash out microbes from the forestomach. Although our data suggest that kangaroos only produce about 27% of the body mass-specific volume of CH4 of ruminants, it remains to be modelled with species-specific growth rates and production conditions whether or not significantly lower CH4 amounts are emitted per kg of meat in kangaroo than in beef or mutton production.

Impacts of visitor number on Kangaroos housed in free-range exhibits.

Free range exhibits are becoming increasingly popular in zoos as a means to enhance interaction between visitors and animals. However very little research exists on the impacts of visitors on animal behaviour and stress in free range exhibits. We investigated the effects of visitor number on the behaviour and stress physiology of Kangaroo Island (KI) Kangaroos, Macropus fuliginosus fuliginosus, and Red Kangaroos, Macropus rufus, housed in two free range exhibits in Australian zoos. Behavioural observations were conducted on individual kangaroos at each site using instantaneous scan sampling to record activity (e.g., vigilance, foraging, resting) and distance from the visitor pathway. Individually identifiable faecal samples were collected at the end of each study day and analysed for faecal glucocorticoid metabolite (FGM) concentration. When visitor number increased, both KI Kangaroos and Red Kangaroos increased the time spent engaged in visitor-directed vigilance and KI Kangaroos also increased the time spent engaged in locomotion and decreased the time spent resting. There was no effect of visitor number on the distance kangaroos positioned themselves from the visitor pathway or FGM concentration in either species. While there are limitations in interpreting these results in terms of fear of visitors, there was no evidence of adverse effects animal welfare in these study groups based on avoidance behaviour or stress physiology under the range of visitor numbers that we studied.

Plasma cholinesterase activity of rats, western grey kangaroos, alpacas, sheep, cattle, and horses.

Plasma cholinesterase activity levels of various species may be of interest to toxicologists or pathologists working with chemicals that interfere with the activity of plasma cholinesterase. We used a pH titration method to measure the plasma cholinesterase activity of six mammalian species. Plasma cholinesterase activity varied up to 50-fold between species: sheep (88 ± 45 nM acetylcholine degraded per ml of test plasma per minute), cattle (94 ± 35), western grey kangaroos (126 ± 92), alpaca (364 ± 70), rats (390 ± 118) and horses (4539 ± 721). We present a simple, effective technique for the assay of plasma cholinesterase activity levels from a range of species. Although labour-intensive, it requires only basic laboratory equipment.

Biphasic Allometry of Cardiac Growth in the Developing Kangaroo Macropus fuliginosus.

Interspecific studies of adult mammals show that heart mass (M(h), g) increases in direct proportion to body mass (M(b), kg), such that M(h) ∝ M(b)(1.00). However, intraspecific studies on heart mass in mammals at different stages of development reveal considerable variation between species, M(h) ∝ M(b)(0.70-1.00). Part of this variation may arise as a result of the narrow body size range of growing placental mammals, from birth to adulthood. Marsupial mammals are born relatively small and offer an opportunity to examine the ontogeny of heart mass over a much broader body size range. Data from 29 western grey kangaroos Macropus fuliginosus spanning 800-fold in body mass (0.084-67.5 kg) reveal the exponent for heart mass decreases significantly when the joey leaves the pouch (ca. 5-6 kg body mass). In the pouch, the heart mass of joeys scales with hyperallometry, M(h(in-pouch)) = 6.39 M(b)(1.10 ± 0.05), whereas in free-roaming juveniles and adults, heart mass scales with hypoallometry, M(h(postpouch)) = 14.2 Mb(0.77 ± 0.08). Measurements of heart height, width, and depth support this finding. The relatively steep heart growth allometry during in-pouch development is consistent with the increase in relative cardiac demands as joeys develop endothermy and the capacity for hopping locomotion. Once out of the pouch, the exponent decreases sharply, possibly because the energy required for hopping is independent of speed, and the efficiency of energy storage during hopping increases as the kangaroo grows. The right:left ventricular mass ratios (0.30-0.35) do not change over the body mass range and are similar to those of other mammals, reflecting the principle of Laplace for the heart.

Morphological and morphometric characteristics of gastric mucosa in western grey kangaroo (Macropus fuliginosus)

The present study was aimed to investigate the morphology and histomorphometry of stomach and gastric mucosa in western grey kangaroo (Macropus fuliginosus). The stomach was composed of three indistinctive separate parts namely sacciform forestomach, tubiform forestomach, and hindstomach. The tubiform forestomach was the main tubular section of the organ. The stomach had a compound lining. The non-glandular mucosa occupied the medial blind sac (MBS) of the sacciform forestomach; the layer covered about one-third of the tubiform forestomach (non-glandular region) and the entire length of the gastric sulcus. The glandular part lined the parietal blind sac (PBS) of sacciform forestomach and the cardiac gland region of tubiform forestomach as well as fundic and pyloric gland regions of the hindstomach. The cardiac mucosa had smooth and folded areas; these were filled with mixed glands. In the fundic glands, the parietal cells outnumbered the chief cells. The pyloric glands were of serous-like in characteristics. In conclusion, gross and histological structures of the stomach of western grey kangaroo are adaptive with its food habitat, which allows thorough mixing of highly fibrous grasses.

Scaling of left ventricle cardiomyocyte ultrastructure across development in the kangaroo Macropus fuliginosus.

The heart and left ventricle of the marsupial western grey kangaroo Macropus fuliginosus exhibit biphasic allometric growth, whereby a negative shift in the trajectory of cardiac growth occurs at pouch exit. In this study, we used transmission electron microscopy to examine the scaling of left ventricle cardiomyocyte ultrastructure across development in the western grey kangaroo over a 190-fold body mass range (0.355-67.5 kg). The volume-density (%) of myofibrils, mitochondria, sarcoplasmic reticuli and T-tubules increase significantly during in-pouch growth, such that the absolute volume (ml) of these organelles scales with body mass (Mb; kg) with steep hyperallometry: 1.41Mb (1.38), 0.64Mb (1.29), 0.066Mb (1.45) and 0.035Mb (1.87), respectively. Maturation of the left ventricle ultrastructure coincides with pouch vacation, as organelle volume-densities scale independent of body mass across post-pouch development, such that absolute organelle volumes scale in parallel and with relatively shallow hypoallometry: 4.65Mb (0.79), 1.75Mb (0.77), 0.21Mb (0.79) and 0.35Mb (0.79), respectively. The steep hyperallometry of organelle volumes and volume-densities across in-pouch growth is consistent with the improved contractile performance of isolated cardiac muscle during fetal development in placental mammals, and is probably critical in augmenting cardiac output to levels necessary for endothermy and independent locomotion in the young kangaroo as it prepares for pouch exit. The shallow hypoallometry of organelle volumes during post-pouch growth suggests a decrease in relative cardiac requirements as body mass increases in free-roaming kangaroos, which is possibly because the energy required for hopping is independent of speed, and the capacity for energy storage during hopping could increase as the kangaroo grows.