Two stages of increased IgA transfer during lactation in the marsupial, trichosurus vulpecula (Brushtail possum)

The polymeric Ig receptor (pIgR) and J chain molecules are involved in the transfer of IgA across the mammary gland epithelia into milk. The J chain binds two IgA molecules to form dimeric IgA, and the pIgR transports this complex through epithelial cells. We report here the cloning of the first marsupial homologues for the pIgR and J chain from the brushtail possum. Marsupial young are born after a short gestation and are less developed than eutherian newborn. The pouch young is completely dependent on milk as its sole source of nutrition during early lactation and this phase can be considered to be equivalent to an external gestation. Two periods of increased expression of pIgR, J chain, and IgA heavy chain mRNAs were observed in the mammary gland during lactation. The first occurs for a brief period after birth of the pouch young and is likely to reflect IgA transfer via the colostrum. The second period of increased expression, which is unique to marsupials, occurs after the early lactation period and just before young exit the pouch. We propose that this represents a second colostral-like phase at the end of the external gestation.     

Factors influencing brushtail possum (

Damage by introduced brushtail possums (Trichosurus vulpecula) to Pinus radiata trees was assessed in 41 compartments of a commercial forestry plantation on the Coromandel Peninsula, New Zealand. All the trees assessed were less than 3 years old. Possum damage in the compartments was low (median prevalence 3.3%) but highly variable (range 0?30%). Eight of 37 measured habitat factors differed significantly (P < 0.05) between the sites with damaged and undamaged trees. The best predictor of mean damage was stand age, but this explained only 21% of the variation in damage among compartments. Including both stand age and New Zealand bracken (Pteridium esculentum) cover improved the model significantly and explained 36% of variation in damage. Damage was apparently unrelated to compartment size, distance from the compartment boundary, and possum den-site availability. Surprisingly, the relationship between browse damage and a trap-catch index of possum abundance was weakly negative (r_S = −0.53, P = 0.05). The dense understorey associated with young pine stands tends to increase possum damage to associated P. radiata trees, but the possums in such stands may be less mobile at ground level and thus less easily trapped. Assessment of stand age and understorey characteristics, together with visual inspection for early signs of damage, is likely to be more cost-effective than possum surveys for identifying forest compartments at risk from possum browse.     

Comparison of two techniques for assessing possum (

Two techniques for assessing possum (Trichosurus vulpecula Kerr) diet from stomach contents ("point-sampling" and "layer- separation") are described and compared. Point-sampling involves sieving stomach contents, systematically selecting fragments from the retained material then, identifying and weighing these. Layer-separation involves separation, identification, and weighing of the discrete layers apparent in most possum stomach contents. In 41 of 43 stomachs examined, we were able to separate discrete layers that nearly always comprised a single food item. To compare the two techniques both were applied to these 41 stomachs, with the point-sampling technique applied as two separate treatments using 1.4-mm and 2.0-mm sieves. There were major differences in diet composition estimates between layer-separation and point-sampling but with few differences between the two point-sampling treatments. Relative to layer-separation, point-sampling underestimated the proportions of food groups with small average fragment size and overestimated those with large fragment size. However, both techniques gave similar frequencies of occurrence for 8 of 10 food groups tested, although the apparent importance of foods based on ranking by frequency of occurrence did not accurately match the ranking based on percent composition data. Identification of material was usually easier and more complete with layer-separation than with point-sampling (i.e., there were virtually no unidentifiable stems and fibre after layer- separation). Layer-separation therefore appears likely to provide a simple technique for diet assessment in possums. Although the technique requires formal validation the existence of layers shows that there can have been little mixing (or digestion) of stomach contents, and therefore, that the layer- separation estimates cannot differ greatly from what was eaten. Techniques that involve sieving possum stomach contents appear to have serious limitations, but may be useful as a last resort when layers contain a mixture of foods, or for stomachs in which the layers are not distinguishable.     

Long-term changes and seasonal patterns in possum (

Possum leaf diet from 1976 to 1989 in the Orongorongo Valley was compared with the diet recorded from four previous years, using faecal analysis. There were large differences in the proportions of species eaten in different seasons and between different years. There was little overall change in the proportion of the main diet tree species, Metrosideros robusta and Weinmannia racemosa, and seasonal increases or declines in one were usually balanced by opposite changes in the other. However, the results of a study of forest composition in the same area showed that living stems of both species declined substantially in abundance, the former mostly before 1978. Melicytus ramiflorus maintained both an important contribution to the diet and its stem density in the forest. The lianes Metrosideros fulgens and Ripogonum scandens both increased their proportion of the diet, but no data were available on their abundance in the study area. At present browse levels, Weinmannia racemosa will become extinct locally, and Metrosideros robusta more rare, especially if drought and higher than average possum densities coincide. Given their large contribution to possum diet, the decline of these species will have a significant effect on possum feeding habits, including increased browsing pressure on Melicytus ramiflorus, Ripogonum scaldens and Metrosideros fulgens. The trend for formerly less palatable tree species to replace those previously important in the diet will continue, with consequent changes in forest species composition.     

Measuring Home-Range Changes Following Density Reduction of Australian Brushtail Possum

It is not clear whether animals consistently change their home ranges in response to density reduction. This is important to understand for better management of pest species where sustained control is required. Our objective was to measure whether home ranges of Australian brushtail possums (Trichosurus vulpecula) change following density reduction, using global positioning system (GPS) tracking. We experimentally reduced the densities of 2 populations (1 high-density at 7 possums/ha and 1 low-density at 1.5 possums/ha) and did not manipulate another population. We then monitored home ranges of individual possums. The high-density manipulated population had a significant increase in home-range size and overlap within 5 weeks following reduction, whereas the other 2 populations did not. This research suggests that changes in possum home ranges following control are likely influenced by the initial density of the pest population. © 2019 The Wildlife Society.     

Hibernation in the mountain pygmy possum Burramys parvus (Marsupialia)

Mountain pygmy possums Burramys parvus (40 g) disappear from their Mt. Kosciusko boulder fields from May to October/November and it is assumed that they hibernate during this time. However, laboratory studies did not observe the characteristic hibernation pattern of placentals, which, throughout the hibernation season, show long bouts of torpor (several days to weeks) that are interrupted by short (< 1 day) normothermic periods. We investigated the pattern of hibernation in juvenile (N = 8) and adult (N = 8) male and female B. parvus in the laboratory at an air temperature that was similar to that in the field during winter. Adults commenced hibernation earlier and hibernated longer (about seven months) than juveniles (about five months). All adult individuals hibernated whereas only six of the eight juveniles did so. Hibernating animals showed distinct seasonal changes in the duration of torpor bouts. Torpor bouts were short (about five days) at the beginning, long (12–20 days) during the middle, and short again at the end of the hibernation season. Normothermic periods were usually shorter than one day. The pattern of the seasonal change of torpor bout duration differed between juveniles and adults and between sexes. Body temperature during mid-hibernation was regulated at about 2 ° c in females and 3 ° C in males and the metabolic rate was similar to that of hibernating placentals.     

Spermiogenesis in the brush-tailed possum,Trichosurus vulpecula (Marsupialia)

Summary Acrosome development in the Australian Brush-tailed possum, Trichosurus vulpecula, displays a number of extraordinary features. This is particularly evident in the later stages of spermiogenesis, when the area of the nuclear surface bounded by the nuclear ring, and covered by the acrosome, is reduced considerable. As a result, the acrosomal material becomes located over its definitive position on the anterior third of the dorsal nuclear surface; in this process it is thrown into a series of folds, and a wide subacrosomal space is formed.Further changes around the time of spermiation result in the release of a spermatozoon in which a thin layer of acrosomal material is closely applied to the nucleus over the area of the definitive location of the acrosome, whilst its margins are greatly extended and project freely away from the nucleus. The latter feature does not appear to have been reported for the sperm of other mammals.The authors would like to thank Dr. D.J.H. Cockayne, Director of the Electron Microscope Unit, University of Sydney, for the generous provision of transmission electron microscope facilities, and Dr. M.R. Dickson, Electron Microscopist in charge, Biomedical Electron Microscope Unit, University of New South Wales, for the use of other facilities. Also, thanks are due to Miss Robin Arnold and Mrs. Eva Vassak of the Department of Histology and Embryology, University of Sydney, for their expert assistance. The assistance of the N.S.W. National Parks and Wildlife Service in the provision of permits to work on these native mammals is acknowledged     

Hind limb blood flow in the brush possum (Trichosurus vulpecula)

1. In the possum (T. vulpecula) sympathetic stimulation, the baroreceptor reflex, exogenous noradrenaline and adrenaline (large dose) produce vasoconstriction in hind limb skeletal muscle. These responses are blocked by α-adrenoceptor blocking agents.2. Exogenous isoprenaline and adrenaline (small dose) produce vasodilatation which is blocked by propranolol.3. Sympathetic cholinergic vasodilator fibres do not appear to exist in the possum.4. At supramaximal frequencies of sympathetic stimulation of the hind limb vascular bed, there is less than maximal response.     

Factors influencing prostatic 5 alpha-reductase activity in possum (Trichosurus vulpecula)

1. There were marked differences in prostatic wts among individual possums, but no evidence of a seasonally related change in wt could be established. It was concluded that the wt differences are mainly due to the changes in secretory activities. After castration the prostate wts fell while after administration of testosterone or oestradiol partially reversed this process. 2. Seven steroid conversion products were isolated from prostatic homogenates incubated with [3H] testosterone; 5 alpha-androstane-3 beta,17 beta-diol forming the highest yield. 3. While the 5 alpha-reductase activity of prostates from intact possums was very low (approx. 8% of the total yield), it increased to over 50% after castration. 4. Administration of testosterone or oestradiol partially reversed the post-castration rise in 5 alpha-reductase, while 17 beta-hydroxy-5 alpha-androstane-3-one (DHT) was ineffective. Administration of porcine FSH-NIH-P2 to both intact or castrated possums caused a marked rise in prostatic 5 alpha-reductase activity. 5. It was concluded that in possum, FSH may have a direct stimulatory effect on prostatic 5 alpha-reductase activity. The results are discussed in relation to placental mammals.     

Hormonal Correlates of Social Rank in an Asocial Species, the Common Brushtail Possum (Trichosurus vulpecula)

Dominance hierarchies play an important role in access to mates or resources in many species. Rank is sometimes correlated with circulating testosterone levels or morphological traits such as body weight. The relationship of glucocorticoid secretion and rank, however, is less clear. In this study, we investigated the relationship of male rank to body weight, circulating testosterone and cortisol concentrations in captive possum triads (Trichosurus vulpecula). We carried out two experiments to examine hierarchy formation and the effects of castration of the dominant male during the non‐breeding season. A third experiment measured the effects of removal of the dominant male from a stable hierarchy during the breeding season. We found that dominant male rank was significantly correlated with higher circulating testosterone levels during periods of hierarchy formation and during the breeding season but not during periods of hierarchy stability in the non‐breeding season. Lack of correlation between plasma testosterone concentration and rank after male castration suggests that stable social rank is not dependent on hormone level and may be more dependent on behavioural traits. Any biocontrol measures that rely on manipulation of hormone levels may be unreliable when applied to unstable hierarchical situations, including the establishment of territories by subadult males, and the pre‐breeding season when circulating testosterone concentrations peak in males and a period of hierarchy establishment may occur.     

Effects of Fertility Control on Behavior and Disease Transmission in Brushtail Possums

Abstract: Fertility control is currently under development for the control of brushtail possums (Trichosurus vulpecula), one of New Zealand's most serious vertebrate pests. Despite intensive research into various methods for achieving infertility, including immunocon-traception and disrupting endocrine control of reproduction, researchers know little about the potential effects of these methods on the behavior of wild possums. We assessed the effects of surgically imposed sterility, either to block fertilization (tubal ligation) or to disrupt endocrine control of fertility (gonadectomy), by using radiotelemetry on the movement patterns and site fidelity of wild brushtail possums. In addition, we assessed the effect of gonadectomy on the transmission rate of a commonly occurring, directly transmitted pathogen in possums, Leptospira interrogans serovar balcanica (hereafter L. balcanica), to determine the effect of any behavioral changes on possum contact rates. Both tubal ligation and gonadectomy of females did not appear to have any appreciable effect on behavior, with sterilized females having space-use patterns and fidelity to seasonal breeding ranges similar to those of fertile females. However, gonadectomy of male possums resulted in a significant reduction of 42% and 47% in the 95% and 70% isopleth seasonal breeding ranges, respectively. Furthermore, the transmission rate of L. balcanica in gonadectomized male and female possums was reduced by 88% and 63%, respectively, compared with that in fertile male and female possums. Overall, these results suggest that fertility control, either by blocking fertilization (e.g., immunocontraception) or by disrupting endocrine control of reproduction (e.g., gonadotropin-releasing hormone vaccines), is unlikely to have an impact on social organization and behavior of brushtail possums in ways that may compromise the efficacy of fertility control for reducing population density. However, the reduction in the transmission rate of L. balcanica indicates that fertility control that interferes with endocrine control of reproduction is likely to reduce the contact rate between possums. This could have implications for the control of other wildlife diseases requiring direct contact for transmission.     

Brush-tailed possum (Trichosurus vulpecula) movements about an erosion-control planting of poplars

Abstract

Live-trapping and radio-tracking were used to monitor the movements of brush-tailed possums in and around an erosion-control planting of poplars. Possums' use of the planted area was monitored by traffic counters and by marking (with Rhodamine B dye) possums which climbed the poplars. The extent of browse damage to the poplars was also recorded. Over a period of 20 months, 358 individuals were trapped, marked, and released, and 50 were fitted with radio transmitter collars. The study area was mapped into nine 100-m-wide annular zones radiating out from the focus, Zone 0, which contained the poplars. Seventy percent of possums assigned to Zone 1 were caught in Zone 0, but only 24%, 5%, and 0% assigned to Zones 2, 3, and 4–8 respectively were caught in Zone 0. Trapping and radio-tracking revealed no increase in the use of the planted area during the spring flush although the poplars were being damaged. Traces of Rhodamine B dye on the possums showed that 87% of animals caught in Zone 0 had visited the poplars, but only 45%, 10%, and 0% of possums caught in Zones 1, 2, and 3–8 respectively. Possums in this area were sedentary and damage to the poplars during spring was attributed to local animals only. Protection of the poplars by fitting expandable plastic sleeves was found to be more cost-effective than aerial poisoning of the surrounding possum population.     

Blowfly succession from possum (Trichosurus vulpecula) carrion in a sheep-farming zone

The significance of brushtail possum, Trichosurus vulpecula Kerr (Diprotodontia: Phalangeridae) carcasses to the succession and production of Diptera species and its relevance to fly strike management in Tasmania, Australia was examined. Calliphora stygia (Fabricius), Lucilia sericata (Meigen) and Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae) were found to be the most abundant and Lucilia cuprina (Wiedemann) (Diptera: Calliphoridae) always the least abundant (< 1%) of the putative primary fly invading species to emerge. Carcasses that were left for up to 15 days in the field before being exposed to flies for 2 days also acted as breeding sites for large numbers of all primary fly species, with the exception of L. cuprina. Ordination analysis revealed no relationship between possum carcasses according to their length of exposure but did show significant negative associations between the number of putative secondary invaders (Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae), Chrysomya varipes (Macquart) (Diptera: Calliphoridae) and putative tertiary flies (Hydrotaea rostrata Robineau-Desvoidy (Diptera: Muscidae)) to the number of C. vicina or C. stygia to emerge. There was enormous variability in the numbers of secondary/tertiary fly species to emerge from carcasses (0-11 450) that negatively correlated with the proportion of all flies to emerge that were primary, and with the mean size of adult L. sericata. Although carcass temperatures, especially those with a large larval population, were elevated, this did not appear to result in significant pre-adult fly mortality. The most important primary fly strike species L. cuprina was only found in insignificant numbers, whereas three other members of the fly strike fauna C. stygia, L. sericata and Ch. rufifacies did use possum carrion as an important breeding resource, but left implications for fly strike management inconclusive.     

Estrogen receptors in the adrenal cortex of the possum (Trichosurus vulpecula)

1. Specific [3H]estradiol binding activity with characteristics of estrogen receptors was found in the cytosols and nuclear extracts of the adrenal cortex proper and special zone of the brushtail possum (Trichosurus vulpecula). 2. The specific estradiol receptor had a sedimentation coefficient on sucrose gradients of approximately 9S and a molecular weight on gel filtration of more than 200,000. The adrenal cortex cytosol binds [3H]estradiol with high affinity (Ka 5.5 X 10(9) M-1), and limited capacity (Bmax 62.7 fmol/mg cytosol prot). In competition experiments with different steroids the receptor showed a high affinity for four estrogens and a very low affinity to androgens, progesterone and cortisol. 3. There was no difference in the affinity and maximum binding capacity of the cytosols from cortex proper in male and female animals, but the binding capacity of the special zone of females was half that of cortex proper. Estradiol receptors were found in the kidney, liver, lung, testis and muscle but only in the adrenal and prostate was the binding capacity relatively high compared with the uterus. 4. The specific binding capacity of [3H]estradiol to cytosols of adrenal cortex at different stages of the estrus cycle and pregnancy was unrelated to that of the uterus. In the adrenal the receptor concentration was lowest at estrus, when uterine concentration was high, while in late pregnancy the binding of adrenal cortex and uterus cytosols was almost the same. 5. The possible physiological significance of the presence of a specific estrogen receptor in male and female possums is discussed.     

Seasonal reproductive periodicity in the male Australian Brush-tailed possum (Trichosurus vulpecula)

The reproduction of the possum, Trichosurus vulpecula (Kerr), was investigated on Banks Peninsula, Canterbury, from 1963 to 1965. The majority of births occur in the autumn, but there is a minor breeding season in the spring. After undergoing an anoestrous period during the summer most females enter oestrus around April. A small proportion of females give birth to a second young during September or October. Reproductive periodicity was also found to occur in the male possum. Although spermatogenesis continues throughout the year in the sexually mature animal there is a marked change in the size of the prostatic urethra at particular periods of the year which correspond to those in which the majority of females are undergoing oestrus. The mean weight of the prostate shows a sixfold increase during the autumn. However only very small changes take place in the size of the testis and epididymis. Changes in size and activity of the prostate correspond with marked changes in the interstitial tissue of the testis. Leydig cells, responsible for the secretion of testosterone, show a great increase in number in animals in which the prostate is enlarged. Associated with the growth of the prostate are changes in the behaviour of the possum. The body weight and fat deposits of the male possum drop markedly at the time of the autumn breeding season.     

Induction of adrenocortical special zone in the male possum (Trichosurus vulpecula)

The induction of adrenocortical special zone (S.Z.) by gonadotrophin administration was studied in male brush tailed possums. Castrated males injected with porcine FSH (NIH-FSH-P2) formed well developed S.Z.s, varying in sizes from 5-20% of the gland's volume. Pregnant mare serum gonadotrophin (PMSG) was ineffective. From adrenal homogenates of FSH treated possums incubated with [3H]-progesterone the major conversion products were 5 beta-reduced steroid metabolites (72%) and cortisol (4%). The conversion products from adrenals of saline and PMSG treated males were cortisol and corticosterone (65%). Of the ten untreated castrates, one had a well developed S.Z. and two had S.Z.s at an early stage of development. Significant 5 beta-reduction of [3H]progesterone was only found in one animal. The plasma FSH concentrations were in intact males 317 +/- 41 ng rat FSH ml-1 (mean +/- SEM) and in castrates 769 +/- 64. The possible reasons for the lack of spontaneous S.Z. formation in intact males are discussed.     

Structure of the oviducal epithelium of the brush-tailed possum (Trichosurus vulpecula)

Observations were made using scanning and transmission electron microscopy and were correlated with measurements of the mean surface area and the percentage area occupied by secretory cells to provide precise interpretation of the morphological data. In cyclic and anoestrous possums the oviducts were lined with elaborate folds of mucosa except in the portion of the isthmus adjacent to the uterus where the pattern was much simplified. The folds decreased in height and number after ovariectomy. Secretion was maximal between oestrus and Day 2 of the cycle when most ovulations take place. Extrusion of vesicles was observed in the ampulla and isthmus at this stage although the process was localized to some extent because groups of cells with actively extruding vesicles were interspersed with others which contained vesicles but otherwise appeared inactive. This is interpreted as a device whereby a constant supply of secretion can be maintained over several days. Secretory activity declined between Days 3 and 8 and the epithelium in mid-cycle (Days 8-18) appeared relatively quiescent. By Day 24 there was morphological and morphometric evidence of a return to oestrous conditions, although vesicles had not yet reappeared in secretory cells. Ciliogenesis was prevalent at this time and is probably related to the ovum transport that will occur several days later.     

Metabolism and defluorination of fluoroacetate in the brush-tailed possum (Trichosurus vulpecula).

The brush-tailed possum (T. vulpecula) from Western Australia was found to be nearly 150 times more resistant to fluoroacetate intoxication in vivo than the same species from South Australia. Acetone powder preparations from the liver of animals from both populations showed similar abilities to convert fluoroacetate into fluorocitrate. Aconitate hydratase activity in liver preparations from both Western Australian and South Australian animals was similarly and competitively inhibited by fluorocitrate. Both animals were capable of defluorinating fluoroacetate at similar rates by a glutathione-dependent enzymic mechanism resulting in the formation of free fluoride ion and S-carboxymethylcysteine. Glutathione was also capable of partial protection against the toxic effects of fluoroacetate in vitro by a further unelucidated mechanism.     

Genomic islands of divergence in the Yellow Tang and the Brushtail Tang Surgeonfishes

The current ease of obtaining thousands of molecular markers challenges the notion that full phylogenetic concordance, as proposed by phylogenetic species concepts, is a requirement for defining species delimitations. Indeed, the presence of genomic islands of divergence, which may be the cause, or in some cases the consequence, of speciation, precludes concordance. Here, we explore this issue using thousands of RAD markers on two sister species of surgeonfishes (Teleostei: Acanthuridae), Zebrasoma flavescens and Z. scopas, and several populations within each species. Species are readily distinguished based on their colors (solid yellow and solid brown, respectively), yet populations and species are neither distinguishable using mitochondrial markers (cytochrome c oxidase 1), nor using 5193 SNPs (pairwise Φst = 0.034). In contrast, when using outlier loci, some of them presumably under selection, species delimitations, and strong population structure follow recognized taxonomic positions (pairwise Φst = 0.326). Species and population delimitation differences based on neutral and selected markers are likely due to local adaptation, thus being consistent with the idea that these genomic islands of divergence arose as a consequence of isolation. These findings, which are not unique, raise the question of a potentially important pathway of divergence based on local adaptation that is only evident when looking at thousands of loci.