Parasites of wombats (family Vombatidae), with a focus on ticks and tick-borne pathogens.

Ticks (Arachnida: Acari) are vectors for pathogens and the biggest threat to animal health. Many Australian ticks are associated with pathogens that impact humans, domestic animals and livestock. However, little is known about the presence or impact of tick-borne pathogens in native Australian wildlife. Wombats are particularly susceptible to the effects of the ectoparasite Sarcoptes scabiei which causes sarcoptic mange, the reason for which is unknown. Factors such as other ectoparasites and their associated pathogens may play a role. A critical understanding of the species of ectoparasites that parasitise wombats and their pathogens, and particularly ticks, is therefore warranted. This review describes the ectoparasites of wombats, pathogens known to be associated with those ectoparasites, and related literature gaps. Pathogens have been isolated in most tick species that typically feed on wombats; however, there are minimal molecular studies to determine the presence of pathogens in any other wombat ectoparasites. The development of next-generation sequencing (NGS) technologies allows us to explore entire microbial communities in ectoparasite samples, allowing fast and accurate identification of potential pathogens in many samples at once. These new techniques have highlighted the diversity and uniqueness of native ticks and their microbiomes, including pathogens of potential medical and veterinary importance. An increased understanding of all ectoparasites that parasitise wombats, and their associated pathogens, requires further investigation.

The use of Cydectin® by wildlife carers to treat sarcoptic mange in free-ranging bare-nosed wombats (Vombatus ursinus).

Wombats suffer from sarcoptic mange, a mite infection that ultimately leads to their death from secondary infections. In 2017, wildlife carers were granted legal approval to treat bare-nosed wombats (Vombatus ursinus) for sarcoptic mange in the field using 4 mL of topical Cydectin® per adult wombat. However, (limited) scientific field trials suggest approved protocols are inadequate which has been supported anecdotally by wildlife carers. Elucidating carer experience is key to holistically advancing understandings of sarcoptic mange treatment. We interviewed 18 wildlife carers regarding the use of Cydectin® to treat free-ranging adult wombats infected with sarcoptic mange which uncovered 43 detailed case studies for examination. Case studies revealed that wildlife carers have used 10-200-mL doses of topical Cydectin® to treat wombats to recovery. These results suggest there is no best-fit for treating wombats in the field, due to individual differences in observed levels of sarcoptic mange severity and differences in wombat behavior. Furthermore, wildlife carers suggested pour-on Cydectin® appeared non-toxic to wombats at rates as high as 200 mL per treatment. We recommend scientific trials should be undertaken to determine the impact and efficacy of the varying treatment regimens, including low and high doses of topical Cydectin® on bare-nosed wombats. This information is required for regulating authorities, and subsequently wildlife carers, and managers, to make fully informed decisions about wombat sarcoptic mange treatment.

A systematic review of moxidectin as a treatment for parasitic infections in mammalian species.

Moxidectin (MOX) is a macrocyclic lactone approved worldwide for the treatment of both endo- and ecto-parasites in many mammalian species. The aim of this study was to assess the efficacy of MOX as a treatment against parasites in a range of mammalian species. An electronic literature search was performed for publications to the 1st September 2020. A total of 205 papers were retrieved and screened against all required criteria; hence, 35 were papers were reviewed in this study. The level of evidence and methodological quality was analysed, where a total of 13 publications were categorised as a 'randomised control trial', seven were categorised as a 'non-randomised control trial' and 15 as an 'experimental control trial'. The overall methodological quality of the publications was considered low, low to moderate, moderate, moderate to high and high in ten, four, twelve, five and a further four, respectively. We assessed the treatment and possible toxicity of MOX in 13 mammalian species, six investigations reported adverse effects to MOX in a small percentage of individuals. The authors reported observed reactions that were typically mild symptoms that did not require additional therapies, and/or resolved themselves. Further studies are needed to assess the efficacy of MOX treatment in a larger number of species, particularly in wildlife.

Mapping out bare-nosed wombat (Vombatus ursinus) burrows with the use of a drone.

BACKGROUND: Wombats are large, nocturnal herbivores that build burrows in a variety of habitats, including grassland communities, and can come into conflict with people. Counting the number of active burrows provides information on the local distribution and abundance of wombats and could prove to be an important management tool to monitor population numbers over time. We compared traditional ground surveys and a new method employing drones, to determine if drones could be used to effectively identify and monitor bare-nosed wombat burrows. RESULTS: We surveyed burrows using both methods in eight 5-ha transects in grassland, that was interspersed with patches of tussock grassland. Ground surveys were conducted by systematically walking transects and searching for burrows. Drone surveys involved programming flights over transects to capture multiple images, from which an orthomosaic image of each transect was produced. These were subsequently viewed using ArcMap to detect burrows. A total of 204 individual burrows were recorded by drone and/or ground survey methods. In grassland, the methods were equally effective in terms of the numbers of burrows detected in transects. In the smaller areas of tussock grassland, ground surveys detected significantly more burrows, because burrow openings were obscured in orthomosaic images by overhanging grasses. There was agreement between the methods as to whether burrows were potentially active or inactive for most burrows in both vegetation communities. However, image interpretation tended to classify grassland burrows as potentially active. Overall time taken to conduct surveys was similar for both methods, but ground surveys utilised three observers and more time in the field. CONCLUSIONS: Drones provide an effective means to survey bare-nosed wombat burrows that are visible from the air, particularly in areas not accessible to observers and vehicles. Furthermore, drones provide alternative options for monitoring burrows at the landscape level, and for monitoring wombat populations based on observable changes in burrow appearance over time.

Digestibility of a new diet for captive short-beaked echidnas (Tachyglossus aculeatus).

Short-beaked echidnas (Tachyglossus aculeatus) are myrmecophages, or ant and termite insectivore specialists, and replicating their exact diet in captivity is problematic. Diets for captive animals often incorporate raw meat, eggs and cat food mixed together with water, and vitamin and mineral supplements. These diets have promoted a number of health problems in captive echidnas, such as gastritis, cystitis, gut impaction, obesity, and diarrhea. A manufactured diet was designed and three echidnas from two zoos were transitioned onto this diet to assess the acceptability and digestibility of this diet for echidnas. The new "test" diet was readily accepted by the echidnas with a 1 week transition period. Daily digestible energy intake was 280 kJ kg-0.75 d-1 , similar to another myrmecophagous species. Digestibility values were above 74% for all macronutrients. It was determined that this diet was an acceptable replacement for the previous diets and it was decided that the remaining echidnas at both institutions would be transitioned to the new diet. The diet will also be used for wild echidnas being rehabilitated in the zoo hospitals prior to release and commercially available within Australia. Further data are being collected to assess the use of this diet for seasonal weight management, transitioning hand-reared puggles and effects on gastrointestinal tract health. Zoo Biol. 36:56-61, 2017. © 2017 Wiley Periodicals, Inc.

Further characterisation of cytokines in macropod marsupials: IL-10 and IL-10Δ3.

Interleukin-10 is an immunomodulatory cytokine that has been implicated, along with IFN-γ, in the disease sequelae of mycobacterial infection. In order to investigate the role of IL-10 in marsupial disease models we sequenced and characterised the IL10 gene in the tammar wallaby (Macropus eugenii) and rufous hare-wallaby (Lagorchestes hirsutus). An isoform IL-10Δ3, in which an in-frame deletion of exon 3 occurs, was discovered in both macropod species. Analysis of wallaby and other reported marsupial IL-10 homologs suggests that while marsupial IL-10 is comparable to that of human IL-10, the predicted IL-10Δ3 protein may play a more complicated role in the modulation of IL-10-directed responses. Expression of the canonical gene and splicing variant was confirmed in both wallabies, and the rufous hare-wallaby showed differential expression across lymph node, spleen and liver, with isoform expression detected in the lymph node. This characterisation and expression of IL-10 in de novo tissues provides a basis for further study into the role of IL-10 in disease models in marsupials.

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.

DNA metabarcoding analysis of the bare-nosed wombat (Vombatus ursinus) diet.

Wombats are native herbivorous grazers that have adapted to Australia's low-quality forage. Studies on diet selection by bare-nosed wombats (Vombatus ursinus) are limited and are either observational or based on microhistological studies. The current study determined the diet of wombats through DNA metabarcoding across five study sites in New South Wales over a one-year period. Metabarcoding was chosen as it is non-invasive, less time consuming and more specific than traditional techniques. The list of 209 plant species identified as eaten by wombats in this study is much higher than previously reported, with grasses being the most common plant group identified in all samples. Most dietary items identified were introduced plant species. Seasonal differences in plants eaten occurred at four of the five study sites and may reflect dietary abundance and floristic composition at different times of year. Further studies are required to determine if the dietary items differ markedly across the entire range of wombats, and if nutrition influences dietary preferences.

Digestibility of two diet items by captive eastern quolls (Dasyurus viverrinus).

The eastern quoll (Dasyurus viverrinus) is a carnivorous Australian marsupial that has undergone significant geographical range contraction since European settlement, and is extinct on the mainland. Nutrition is not well researched in captive eastern quolls, and captive diets often consist of commercial pet foods as opposed to raw meat or insect diets. Improving nutrition will enhance reproductive output and ensure suitable numbers of quolls are bred to be used in translocation programs. The present study analyzed the composition of kangaroo mince and chicken necks, and the digestibility of these items, in a captive environment. The quolls had high apparent total tract digestibility on the chicken neck and kangaroo mince treatments (DM 83-88%, GE 95-97%, protein 94-97%, and lipids 94-95%, respectively). The apparent total tract digestibility of DM, GE, and proteins was significantly higher (t14= 2.465, P < 0.05; t14= 2.489, P < 0.05; t14= 5.470, P < 0.01, respectively) on the kangaroo mince treatment compared with the chicken neck treatment. This study provides the first data on Cu (-18-37%), S (86-95%), and Zn (26-28%) apparent total tract digestibility in a Dasyurid. Data gathered during this study can be used to improve management practices for captive quolls, including diet formulation and mineral supplementation.

Assessment of the diet of the critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii) using DNA metabarcoding.

Invasive buffel grass (Cenchrus ciliaris) is considered a threat to the critically endangered northern hairy-nosed wombat (Lasiorhinus krefftii; NHW). Buffel grass outcompetes native grasses, reducing availability of native food items for NHW, and causes more intense fires due to the large volumes of dead matter it produces. Previous studies suggested buffel grass was increasing in the diet; however, the diet of the NHW has not been reassessed for over two decades and was limited to Epping Forest National Park, with the population at Richard Underwood Nature Refuge having never been assessed. The recently released 2022 Recovery Action Plan for the species outlined objectives to assist its conservation and recommended the impact of buffel grass on the species' diet be investigated. This study aimed to determine: (1) which plant species are being consumed by the NHW; (2) the differences in the diet between sites; (3) differences between seasons; and (4) the abundance of buffel grass in the diet. The diet was assessed using DNA metabarcoding of scat samples collected from both sites from winter 2020 to spring 2021. Site and season significantly affected the diet of the NHW. Buffel grass dominated the diet and has increased in the diet since past assessments. The findings of this study will support population and habitat management of the critically endangered NHW. Enhanced knowledge of dietary items consumed at both sites will also assist efforts to locate additional sites suitable for translocation.

Spatial and temporal patterns of sarcoptic mange in wombats using the citizen science tool, WomSAT.

There is currently limited information regarding the levels of infection and distribution of sarcoptic mange in the wombat population throughout Australia. We analyzed cases of sarcoptic mange in bare-nosed wombats reported into WomSAT, a website and mobile phone application where citizen scientists can upload sightings of wombats, burrows, and sarcoptic mange status. We used Maxent software to predict locations and the environmental factors associated with sarcoptic mange occurrence in bare-nosed wombats. A total of 1379 sarcoptic mange-infected and 3043 non-sarcoptic mange-infected wombats were reported by 674 and 841 citizen scientists, respectively. Of all the wombats reported to WomSAT from 2015 to 2019, 31.2% were infected with sarcoptic mange. Sarcoptic mange in bare-nosed wombats was reported in 502 suburbs across four states. New South Wales had the highest number of sarcoptic mange cases reported to WomSAT. There was no statistically significant seasonal variation of sarcoptic mange levels in bare-nosed wombats. The model showed that Euclidean distance to urban areas was the highest contributing factor for sarcoptic mange occurrence. As distance to urban areas decreased, the suitability for sarcoptic mange increased. Annual precipitation was the next contributing factor in the model, with higher rainfall of 400-700 mm correlating to an increase in sarcoptic mange occurrence. As the data collected to date have provided the largest-scale contemporary distribution of sarcoptic mange in wombats, data should continue to be collected by citizen scientists as it is an easy and low-cost method of collecting data over large areas. We suggest targeting the identified hotspot areas and more site-specific studies for studying and mitigating sarcoptic mange in bare-nosed wombats.

Embryonic communication in the nest: metabolic responses of reptilian embryos to developmental rates of siblings.

Incubation temperature affects developmental rates and defines many phenotypes and fitness characteristics of reptilian embryos. In turtles, eggs are deposited in layers within the nest, such that thermal gradients create independent developmental conditions for each egg. Despite differences in developmental rate, several studies have revealed unexpected synchronicity in hatching, however, the mechanisms through which synchrony are achieved may be different between species. Here, we examine the phenomenon of synchronous hatching in turtles by assessing proximate mechanisms in an Australian freshwater turtle (Emydura macquarii). We tested whether embryos hatch prematurely or developmentally compensate in response to more advanced embryos in a clutch. We established developmental asynchrony within a clutch of turtle eggs and assessed both metabolic and heart rates throughout incubation in constant and fluctuating temperatures. Turtles appeared to hatch at similar developmental stages, with less-developed embryos in experimental groups responding to the presence of more developed eggs in a clutch by increasing both metabolic and heart rates. Early hatching did not appear to reduce neuromuscular ability at hatching. These results support developmental adjustment mechanisms of the 'catch-up hypothesis' for synchronous hatching in E. macquarii and implies some level of embryo-embryo communication. The group environment of a nest strongly supports the development of adaptive communication mechanisms between siblings and the evolution of environmentally cued hatching.

Morphological identification of ticks and molecular detection of tick-borne pathogens from bare-nosed wombats (Vombatus ursinus).

BACKGROUND: Ticks are obligate haematophagous ectoparasites of vertebrate hosts and transmit the widest range of pathogenic organisms of any arthropod vector. Seven tick species are known to feed on bare-nosed wombats (Vombatus ursinus), in addition to the highly prevalent Sarcoptes scabiei mite which causes fatal sarcoptic mange in most bare-nosed wombat populations. Little is known about the pathogens carried by most wombat ticks or how they may impact wombats and wombat handlers. METHODS: Wombat ticks were sourced from wildlife hospitals and sanctuaries across Australia and identified to species level using taxonomic keys. Genomic DNA was extracted from a subsample, and following the amplification of the bacterial 16S rRNA gene V3-V4 hypervariable region, next-generation sequencing (NGS) on the Illumina MiSeq platform was used to assess the microbial composition. RESULTS: A total of 447 tick specimens were collected from 47 bare-nosed wombats between January 2019 and January 2020. Five species of ticks were identified comprising wombat tick Bothriocroton auruginans (n = 420), wallaby tick Haemaphysalis bancrofti (n = 8), bush tick Haemaphysalis longicornis (n = 3), common marsupial tick Ixodes tasmani (n = 12), and Australian paralysis tick Ixodes holocyclus (n = 4). Tick infestations ranged from one to 73 ticks per wombat. The wombat tick was the most prevalent tick species comprising 94% of the total number of samples and was present on 97.9% (46/47) of wombat hosts. NGS results revealed the 16S rRNA gene diversity profile was predominantly Proteobacteria (55.1%) followed by Firmicutes (21.9%) and Actinobacteria (18.4%). A species of Coxiella sharing closest sequence identity to Coxiella burnetii (99.07%), was detected in 72% of B. auruginans and a Rickettsiella endosymbiont dominated the bacterial profile for I. tasmani. CONCLUSIONS: A new host record for H. longicornis is the bare-nosed wombat. One adult male and two engorged adult female specimens were found on an adult male wombat from Coolagolite in New South Wales, and more specimens should be collected to confirm this host record. The most prevalent tick found on bare-nosed wombats was B. auruginans, confirming previous records. Analysis of alpha-diversity showed high variability across both sample locations and instars, similar to previous studies. The detection of various Proteobacteria in this study highlights the high bacterial diversity in native Australian ticks.

Red-tailed phascogales: A review of their biology and importance as model marsupial species.

There are many limitations when using traditional laboratory species. Limits on variation, may result in limited outcomes, at both the species and individual level, due to different individuals/species having diverse physiological processes, or differing molecular and genetic mechanisms. By using a variety of model species, we will be able to develop creative solutions to biological problems and identify differences of which we were not previously aware. The laboratory mouse has been a suitable model species for various mammalian studies, however most are bred specifically for laboratory research with limited variability due to selective breeding. Marsupial models offer unique research opportunities compared to eutherian models. We believe that there should be an expansion in marsupial model species, and the introduction of the red-tailed phascogale (Phascogale calura), a dasyurid marsupial, should be one of them. Phascogales are easily managed in captivity, and there are now multiple studies involving their development, reproduction, nutrition, behavior and immune system, which can serve as a baseline for future studies. The addition of the phascogale as a model species will improve future mammalian studies by introducing variability and offer alternate solutions to biological problems, particularly in the areas of genetics, nutrition, immunology, the neuro-endocrine system, and ageing, due to their semelparous reproductive strategy and hence, subsequent predictive physiology. In this review, we provide information based on existing research on red-tailed phascogales to support their inclusion as a model species.

Mosquito-Borne Viruses and Non-Human Vertebrates in Australia: A Review.

Mosquito-borne viruses are well recognized as a global public health burden amongst humans, but the effects on non-human vertebrates is rarely reported. Australia, houses a number of endemic mosquito-borne viruses, such as Ross River virus, Barmah Forest virus, and Murray Valley encephalitis virus. In this review, we synthesize the current state of mosquito-borne viruses impacting non-human vertebrates in Australia, including diseases that could be introduced due to local mosquito distribution. Given the unique island biogeography of Australia and the endemism of vertebrate species (including macropods and monotremes), Australia is highly susceptible to foreign mosquito species becoming established, and mosquito-borne viruses becoming endemic alongside novel reservoirs. For each virus, we summarize the known geographic distribution, mosquito vectors, vertebrate hosts, clinical signs and treatments, and highlight the importance of including non-human vertebrates in the assessment of future disease outbreaks. The mosquito-borne viruses discussed can impact wildlife, livestock, and companion animals, causing significant changes to Australian ecology and economy. The complex nature of mosquito-borne disease, and challenges in assessing the impacts to non-human vertebrate species, makes this an important topic to periodically review.

Developmental and comparative immunology single-cell transcriptome analysis of the B-cell repertoire reveals the usage of immunoglobulins in the gray short-tailed opossum (Monodelphis domestica).

B-cells are key to humoral immunity, are found in multiple lymphoid organs, and have the unique ability to mediate the production of antigen-specific antibodies in the presence of pathogens. The marsupial immunoglobulin (Ig) heavy (H) chain locus encodes four constant region isotypes, IgA, IgG, IgM and IgE, but no IgD, and there are two light (L) chain isotypes, lambda (Igλ) and kappa (Igκ). To gain an understanding of the marsupial humoral immune system, B-cell transcriptomes generated by single-cell RNA sequencing from gray short-tailed opossum (Monodelphis domestica) splenocytes, and peripheral blood mononuclear cells were analysed. The cells used were from a single unimmunized animal and the majority of B-cells were transcribing IgM heavy chains. The ratio of Ig light chain use was roughly 2:1, Igλ:Igκ in this individual. This was not predicted due to Igκ being the more complex of the two L chain loci. The variable (V) gene segment pairs used in individual B-cells confirm greater diversity provided by the L chain V. This study is the first to report on using single cell analysis to investigate Ig repertoires in a marsupial and confirms a number of prior hypothesis, as well as revealing some surprises.

The external ear morphology and presence of tragi in Australian marsupials.

Multiple studies have described the anatomy and function of the external ear (pinna) of bats, and other placental mammals, however, studies of marsupial pinna are largely absent. In bats, the tragus appears to be especially important for locating and capturing insect prey. In this study, we aimed to investigate the pinnae of Australian marsupials, with a focus on the presence/absence of tragi and how they may relate to diet. We investigated 23 Australian marsupial species with varying diets. The pinnae measurements (scapha width, scapha length) and tragi (where present) were measured. The interaural distance and body length were also recorded for each individual. Results indicated that all nectarivorous, carnivorous, and insectivorous species had tragi with the exception of the insectivorous striped possum (Dactylopsila trivirgata), numbat (Myrmecobius fasciatus), and nectarivorous sugar glider (Petaurus breviceps). No herbivorous or omnivorous species had tragi. Based on the findings in this study, and those conducted on placental mammals, we suggest marsupials use tragi in a similar way to placentals to locate and target insectivorous prey. The Tasmanian devil (Sarcophilus harrisii) displayed the largest interaural distance that likely aids in better localization and origin of noise associated with prey detection. In contrast, the smallest interaural distance was exhibited by a macropod. Previous studies have suggested the hearing of macropods is especially adapted to detect warnings of predators made by conspecifics. While the data in this study demonstrate a diversity in pinnae among marsupials, including presence and absence of tragi, it suggests that there is a correlation between pinna structure and diet choice among marsupials. A future study should investigate a larger number of individuals and species and include marsupials from Papua New Guinea, and Central and South America as a comparison.

Marsupial and monotreme milk-a review of its nutrient and immune properties.

All mammals are characterized by the ability of females to produce milk. Marsupial (metatherian) and monotreme (prototherian) young are born in a highly altricial state and rely on their mother's milk for the first part of their life. Here we review the role and importance of milk in marsupial and monotreme development. Milk is the primary source of sustenance for young marsupials and monotremes and its composition varies at different stages of development. We applied nutritional geometry techniques to a limited number of species with values available to analyze changes in macronutrient composition of milk at different stages. Macronutrient energy composition of marsupial milk varies between species and changes concentration during the course of lactation. As well as nourishment, marsupial and monotreme milk supplies growth and immune factors. Neonates are unable to mount a specific immune response shortly after birth and therefore rely on immunoglobulins, immunological cells and other immunologically important molecules transferred through milk. Milk is also essential to the development of the maternal-young bond and is achieved through feedback systems and odor preferences in eutherian mammals. However, we have much to learn about the role of milk in marsupial and monotreme mother-young bonding. Further research is warranted in gaining a better understanding of the role of milk as a source of nutrition, developmental factors and immunity, in a broader range of marsupial species, and monotremes.

Immunogenetics of marsupial B-cells.

Marsupials and eutherians are mammals that differ in their physiological traits, predominately their reproductive and developmental strategies; eutherians give birth to well-developed young, while marsupials are born highly altricial after a much shorter gestation. These developmental traits also result in differences in the development of the immune system of eutherian and marsupial species. In eutherians, B-cells are the key to humoral immunity as they are found in multiple lymphoid organs and have the unique ability to mediate the production of antigen-specific antibodies in the presence of extracellular pathogens. The development of B-cells in marsupials has been reported and hypothesised to be similar to that of eutherians, except that haematopoiesis occurs in the liver, postpartum, until the bone marrow fully matures. In eutherians, specific genes are linked to specific stages in B-cell development, maturation, and differentiation processes, and have been identified including immunoglobulins (heavy and light chains), cluster of differentiation markers (CD10, 19, 34 and CD79α/ß), signal transduction molecules (BTK, Lyn and Syk) and transcriptional regulators (EBF1, E2A, and Pax5). This review aims to discuss the known similarities and differences between marsupial and eutherian B-cells, in regards to their genetic presence, homology, and developmental stages, as well as to highlight the areas requiring further investigation. By enhancing our understanding of the genes that are involved with B-cells in the marsupial lineage, it will, in turn, aid our understanding of the marsupial immune system and support the development of specific immunological reagents for research and wildlife conservation purposes.