The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Fritz Geiser - One of the best experts on this subject based on the ideXlab platform.
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Seasonal changes in the thermoenergetics of the marsupial Sugar Glider, Petaurus breviceps.
Journal of comparative physiology. B Biochemical systemic and environmental physiology, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Little information is available on seasonal changes in thermal physiology and energy expenditure in marsupials. To provide new information on the subject, we quantified how body mass, body composition, metabolic rate, maximum heat production, body temperature and thermal conductance change with season in Sugar Gliders (Petaurus breviceps) held in outdoor aviaries. Sugar Gliders increased body mass in autumn to a peak in May/June, which was caused to a large extent by an increase in body fat content. Body mass then declined to minimum values in August/September. Resting metabolic rate both below and above the thermoneutral zone (TNZ) was higher in summer than in winter and the lower critical temperature of the TNZ occurred at a higher ambient temperature (Ta) in summer. The basal metabolic rate was as much as 45% below that predicted from allometric equations for placental mammals and was about 15% lower in winter than in summer. In contrast, maximum heat production was raised significantly by about 20% in winter. This, together with an approximately 20% decrease in thermal conductance, resulted in a 13°C reduction of the minimum effective Ta Gliders were able to withstand. Our study provides the first evidence that, despite the apparent lack of functional brown adipose tissue, Sugar Gliders are able to significantly increase heat production in winter. Moreover, the lower thermoregulatory heat production at most Tas in winter, when food in the wild is scarce, should allow them to reduce energy expenditure.
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effects of helium oxygen and temperature on aerobic metabolism in the marsupial Sugar Glider petaurus breviceps
Physiological and Biochemical Zoology, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Abstract Helox (79% helium and 21% oxygen) has often been used for thermobiological studies, primarily because helium is thought to be metabolically inert and to produce no adverse effects other than increasing heat loss. However, these assumptions have been questioned. As basal metabolic rate (BMR) represents maintenance energy requirements for vital body functions, potential physiological effects of helox should be reflected in changes of BMR. In this study, Sugar Gliders were subjected to both air and helox atmospheres over a wide range of Ta's, including the thermoneutral zone (TNZ), to determine (1) whether helox has any influence other than on heat loss and (2) the maximum heat production (HPmax) and thermal limits of this species. Although thermal conductance in the TNZ increased in helox, BMR was similar in air and helox ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage...
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Effects of helium/oxygen and temperature on aerobic metabolism in the marsupial Sugar Glider, Petaurus breviceps.
Physiological and biochemical zoology : PBZ, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Abstract Helox (79% helium and 21% oxygen) has often been used for thermobiological studies, primarily because helium is thought to be metabolically inert and to produce no adverse effects other than increasing heat loss. However, these assumptions have been questioned. As basal metabolic rate (BMR) represents maintenance energy requirements for vital body functions, potential physiological effects of helox should be reflected in changes of BMR. In this study, Sugar Gliders were subjected to both air and helox atmospheres over a wide range of Ta's, including the thermoneutral zone (TNZ), to determine (1) whether helox has any influence other than on heat loss and (2) the maximum heat production (HPmax) and thermal limits of this species. Although thermal conductance in the TNZ increased in helox, BMR was similar in air and helox ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage...
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Development of thermoregulation in the Sugar Glider Petaurus breviceps (Marsupialia: Petauridae)
Journal of Zoology, 2000Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Young, relatively undeveloped Sugar Gliders Petaurus breviceps have been observed to be left alone in the nest while the mother forages and may be subject to considerable thermal or energetic stress. As no information is available on the development of thermoregulation in this species, which begins reproduction in winter, we measured resting metabolic rate (RMR), body temperature (T b) and thermal conductance over a range of ambient temperatures (T a) in 10 Sugar Gliders from c. 55 days of age until they had grown to adult size. Sugar Gliders were unable to maintain a stable T b over a T a range of 30‐158C until the age of 95‐100 days, although they raised RMR somewhat as T a decreased. Further growth resulted in a steady decrease in mass-specific RMR, an increase in T b and a substantial decrease in thermal conductance. Our study shows that young Gliders below the age of 100 days rely largely on heat produced by adults to maintain a high T b, but are well able to cope with regular falls in T b of > 108C and a concomitant decrease of RMR. This thermal tolerance and reduction in energy expenditure should allow the mother to forage and replenish her own body fuels while her offspring are left alone in the nest.
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Weather Patterns and Daily Torpor in Free ranging Animals
Life in the Cold, 2000Co-Authors: Gerhard Körtner, Fritz GeiserAbstract:Torpor was investigated in free-ranging tawny frogmouths (Podargus strigoides: Caprimulgiformes) and Sugar Gliders (Petaurus breviceps: Marsupialia) near Armidale, NSW, Australia. Both nocturnal species entered torpor regularly. Torpor was most frequent in June/July/August (frogmouth: 50.4%; Sugar Glider: 22.3%), the three coldest months of the year. Both species entered torpor preferably during their normal activity phase. While Sugar Gliders extended torpor into the rest phase, frogmouths always aroused before sunrise, but often commenced a second torpor bout around dawn. Low Ta was the main stimulus for the expression of torpor, but for Sugar Gliders rainfall was also important. It appears that inclement weather conditions not only increase thermoregulatory costs, but more importantly, prevent successful foraging in both species. Therefore, torpor cannot balance the daily energy budget, but is nevertheless important to stretch body energy reserves, which can be replenished only irregularly.
Dejan Stojanovic - One of the best experts on this subject based on the ideXlab platform.
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When is a native species invasive? Incursion of a novel predatory marsupial detected using molecular and historical data
Diversity and Distributions, 2018Co-Authors: Catriona D. Campbell, Dejan Stojanovic, Stephen D. Sarre, Bernd Gruber, Kathryn Medlock, Stephen Harris, Anna J. Macdonald, Clare E. HolleleyAbstract:Aim Range expansions facilitated by humans or in response to local biotic or abiotic stressors provide the opportunity for species to occupy novel environments. Classifying the status of newly expanded populations can be difficult, particularly when the timing and nature of the range expansion are unclear. Should native species in new habitats be considered invasive pests or actively conserved? Here, we present an analytical framework applied to an Australian marsupial, the Sugar Glider (Petaurus breviceps), a species that preys upon on an endangered parrot in Tasmania, and whose provenance was uncertain. Location Tasmania, Australia. Methods We conducted an extensive search of historical records for Sugar Glider occurrences in Tasmania. Source material included museum collection data, early European expedition logs, community observation records, and peer‐reviewed and grey literature. To determine the provenance of the Tasmanian population, we sequenced two mitochondrial genes and one nuclear gene in Tasmanian animals (n = 27) and in individuals across the species' native range. We then estimated divergence times between Tasmania and southern Australian populations using phylogenetic and Bayesian analyses. Results We found no historical evidence of Sugar Gliders occurring in Tasmania prior to 1835. All Tasmanian individuals (n = 27) were genetically identical at the three genes surveyed here with those individuals being 0.125% divergent from individuals from a population in Victoria. Bayesian analysis of divergence between Tasmanian individuals and southern Australian individuals suggested a recent introduction of Sugar Gliders into Tasmania from southern Australia. Main conclusions Molecular and historical data demonstrate that Tasmanian Sugar Gliders are a recent, post‐European, anthropogenic introduction from mainland Victoria. This result has implications for the management of the species in relation to their impact on an endangered parrot. The analytical framework outlined here can assist environmental managers with the complex task of assessing the status of recently expanded or introduced native species.
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Projected direct and indirect effects of climate change on the Swift Parrot, an endangered migratory species
Emu - Austral Ornithology, 2016Co-Authors: Luciana L. Porfirio, R. M. Harris, Dejan Stojanovic, Mathew H. Webb, Brendan MackeyAbstract:Assessing future changes in the suitability of the climate niche for interacting species across different trophic levels can identify direct and indirect effects of climate change that may be missed using single-species approaches. We use ensembles of species distribution models based on a dynamically down-scaled regional climate model to project the future suitability of climate for the Swift Parrot (Lathamus discolor), its primary food and habitat resources (Tasmanian Blue Gum (Eucalyptus globulus) and Swamp Gum (E. ovata)), and an introduced nest predator, the Sugar Glider (Petaurus breviceps). These results are combined with layers representing mature forest and fire danger to identify locations that may act as refuges for the Swift Parrot from fire, deforestation and predation under baseline and future climates. Almost a quarter of the nesting habitat of Swift Parrots is projected to become climatically unsuitable by the end of the 21st century, but large areas may remain climatically suitable for both Swift Parrots and their food trees. However, loss of forests and the presence of Sugar Gliders are likely to limit the availability of high-quality habitat. Offshore islands that the Sugar Glider is unable to colonise or where future climate is not projected to be suitable for the Sugar Glider may be the only places, in the near future, where the Swift Parrot will be protected from nest predation by this introduced species.
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a severe predator induced population decline predicted for endangered migratory swift parrots lathamus discolor
Biological Conservation, 2015Co-Authors: Robert Heinsohn, Matthew Webb, Robert C Lacy, Aleks Terauds, Rachael Alderman, Dejan StojanovicAbstract:Identifying the impact of introduced predators on endangered prey populations is critical for conservation management. Population viability analysis (PVA) becomes a valuable tool for quantifying such impacts when high quality life history data are available but, surprisingly, predictions from PVA of future population decline have seldom been used directly to assess conservation status. Here we synthesise new research on the unusual life history of the endangered swift parrot Lathamus discolor, an austral migrant that breeds in Tasmania, Australia. Swift parrots are challenging to monitor because (1) spatio-temporal fluctuation in food availability causes them to select entirely different breeding sites each year over a 10,000 km 2 range, and (2) they suffer high but variable rates of predation from introduced Sugar Gliders Petaurus breviceps depending on where they breed. 50.9% of nesting females on the main island of Tasmania were killed by Sugar Gliders while incubating eggs, but there was no predation from this source on offshore islands. Over four years 16.5% (0–29%) of the population bred on offshore islands. We use PVAs to examine the likely extent of future population decrease due to Sugar Glider predation, and demonstrate that the remaining swift parrot population is likely to decrease by 78.8–94.7% (mean over four models = 86.9%) over only three generations (12–18 years). Our models offer a rare example of the use of PVAs for assessing impending population decline and conservation status in species that are challenging to monitor. In this case they support a change of status for swift parrots from ‘‘Endangered’’ to ‘Critically Endangered’ under IUCN criteria.
Adrian J. Bradley - One of the best experts on this subject based on the ideXlab platform.
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Plasma androgen, social position, and response to GnRH in the marsupial Sugar Glider Petaurus breviceps (Marsupialia: Petauridae)
Journal of Zoology, 1997Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:The effect of gonadotrophin-releasing hormone GnRH on plasma testosterone was examined in male Sugar Gliders Petaurus breviceps that were judged to occupy either the highest or lowest position in stable colonies consisting of up to four males and two females. Experiment were carried out at a time when breeding occurred in two of the three colonies, as evidenced by the presence of pouch young.
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Behavioral and endocrinological correlates of social status in the male Sugar Glider (Petaurus breviceps Marsupialia: Petauridae).
Physiology & behavior, 1994Co-Authors: J. Mallick, D. M. Stoddart, Ivor H. Jones, Adrian J. BradleyAbstract:Socially dominant male Sugar Gliders are heavier than socially subordinate males, have higher plasma testosterone and lower cortisol concentrations, win more social encounters, scan the arena more, scent-mark more, and are more active and move more quickly, even though they spend more time in the colony nesting box. When they are transferred into a foreign stable colony there is an impressive reversal of behavioral measures and a concomitant decrease in concentration of plasma testosterone and rise in cortisol that is apparent over the first 3 weeks of observation.
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The dorsal paracloacal gland and its relationship with seasonal changes in cutaneous scent gland morphology and plasma androgen in the marsupial Sugar Glider (Petaurus breviceps; Marsupialia: Petauridae)
Journal of Zoology, 1993Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:A study spanning two breeding seasons was carried out to examine changes in the size of the dorsal paracloacal glands and testes in the marsupial Sugar Glider Petaurus breviceps Waterhouse 1839. These changes were related to seasonal increases in the plasma testosterone concentration and to morphological changes in the frontal and gular cutaneous scent glands of males. Both dorsal paracloacal glands and testes underwent a seasonal cycle of development which reached its maximum during the June-September breeding season. These changes coincided with an increase in the plasma testosterone concentration and with the increase in activity of certain cell types within the frontal and gular glands. Castration caused a significant decrease in the size of the dorsal paracloacal glands, while androgen replacement was effective in restoring the glands to their pre-castration size thus demonstrating the influence of androgens upon the activity of these glands. The synchronization which exists between plasma testosterone concentration, cutaneous scent gland morphology and the size of the dorsal paracloacal glands of males, suggests that the dorsal paracloacal glands, or more likely their secretions, are important in social organization in this species.
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Seasonal changes in plasma androgens, glucocorticoids and glucocorticoid-binding proteins in the marsupial Sugar Glider Petaurus breviceps.
The Journal of endocrinology, 1992Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:An investigation spanning two breeding seasons was carried out to examine endocrine changes associated with reproduction in a wild population of the marsupial Sugar Glider Petaurus breviceps, a small arboreal gliding possum.
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Olfactory Biology of the Marsupial Sugar Glider — A Preliminary Study
Chemical Signals in Vertebrates 6, 1992Co-Authors: D. Michael Stoddart, Adrian J. Bradley, K. L. HynesAbstract:The marsupial Sugar Glider, Petatrrus breviceps Waterhouse, is a small gliding possum which inhabits many forest types along Australia’s east and northern coasts, from southern Tasmania to Darwin, and extends northwards into Papua New Guinea (Stralhan 1983). It is abundant and widespread in Tasmania, following a successful introduction in the mid-1850s. Sugar Gliders are almost exclusively arboreal and seldom venture to the forest floor. Their diet is mainly invertebrates, though the Sugary sap from trees of the genus Eucalyptus and the nectar and pollen from Banksia are eagerly sought during winter. Highly social mammals, Sugar Gliders nest and breed in tree holes in small colonies of about 6 to 10 individuals (Suckling 1984). While group structure is not fully understood it is usual for more than ore fully mature male to be present. In Tasmania they breed once each year, mating in the winter (July to early September) and give birth after a gestation of about 16 days. A single young, or occasionally twins, remain in the pouch attached to a teat for a further two months. It is possible for females to carry a second litter but this usually occurs only when the first has been lost (Stoddart and Bradley, in press).
Joanne C. Holloway - One of the best experts on this subject based on the ideXlab platform.
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Seasonal changes in the thermoenergetics of the marsupial Sugar Glider, Petaurus breviceps.
Journal of comparative physiology. B Biochemical systemic and environmental physiology, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Little information is available on seasonal changes in thermal physiology and energy expenditure in marsupials. To provide new information on the subject, we quantified how body mass, body composition, metabolic rate, maximum heat production, body temperature and thermal conductance change with season in Sugar Gliders (Petaurus breviceps) held in outdoor aviaries. Sugar Gliders increased body mass in autumn to a peak in May/June, which was caused to a large extent by an increase in body fat content. Body mass then declined to minimum values in August/September. Resting metabolic rate both below and above the thermoneutral zone (TNZ) was higher in summer than in winter and the lower critical temperature of the TNZ occurred at a higher ambient temperature (Ta) in summer. The basal metabolic rate was as much as 45% below that predicted from allometric equations for placental mammals and was about 15% lower in winter than in summer. In contrast, maximum heat production was raised significantly by about 20% in winter. This, together with an approximately 20% decrease in thermal conductance, resulted in a 13°C reduction of the minimum effective Ta Gliders were able to withstand. Our study provides the first evidence that, despite the apparent lack of functional brown adipose tissue, Sugar Gliders are able to significantly increase heat production in winter. Moreover, the lower thermoregulatory heat production at most Tas in winter, when food in the wild is scarce, should allow them to reduce energy expenditure.
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effects of helium oxygen and temperature on aerobic metabolism in the marsupial Sugar Glider petaurus breviceps
Physiological and Biochemical Zoology, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Abstract Helox (79% helium and 21% oxygen) has often been used for thermobiological studies, primarily because helium is thought to be metabolically inert and to produce no adverse effects other than increasing heat loss. However, these assumptions have been questioned. As basal metabolic rate (BMR) represents maintenance energy requirements for vital body functions, potential physiological effects of helox should be reflected in changes of BMR. In this study, Sugar Gliders were subjected to both air and helox atmospheres over a wide range of Ta's, including the thermoneutral zone (TNZ), to determine (1) whether helox has any influence other than on heat loss and (2) the maximum heat production (HPmax) and thermal limits of this species. Although thermal conductance in the TNZ increased in helox, BMR was similar in air and helox ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage...
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Effects of helium/oxygen and temperature on aerobic metabolism in the marsupial Sugar Glider, Petaurus breviceps.
Physiological and biochemical zoology : PBZ, 2001Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Abstract Helox (79% helium and 21% oxygen) has often been used for thermobiological studies, primarily because helium is thought to be metabolically inert and to produce no adverse effects other than increasing heat loss. However, these assumptions have been questioned. As basal metabolic rate (BMR) represents maintenance energy requirements for vital body functions, potential physiological effects of helox should be reflected in changes of BMR. In this study, Sugar Gliders were subjected to both air and helox atmospheres over a wide range of Ta's, including the thermoneutral zone (TNZ), to determine (1) whether helox has any influence other than on heat loss and (2) the maximum heat production (HPmax) and thermal limits of this species. Although thermal conductance in the TNZ increased in helox, BMR was similar in air and helox ( \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage...
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Development of thermoregulation in the Sugar Glider Petaurus breviceps (Marsupialia: Petauridae)
Journal of Zoology, 2000Co-Authors: Joanne C. Holloway, Fritz GeiserAbstract:Young, relatively undeveloped Sugar Gliders Petaurus breviceps have been observed to be left alone in the nest while the mother forages and may be subject to considerable thermal or energetic stress. As no information is available on the development of thermoregulation in this species, which begins reproduction in winter, we measured resting metabolic rate (RMR), body temperature (T b) and thermal conductance over a range of ambient temperatures (T a) in 10 Sugar Gliders from c. 55 days of age until they had grown to adult size. Sugar Gliders were unable to maintain a stable T b over a T a range of 30‐158C until the age of 95‐100 days, although they raised RMR somewhat as T a decreased. Further growth resulted in a steady decrease in mass-specific RMR, an increase in T b and a substantial decrease in thermal conductance. Our study shows that young Gliders below the age of 100 days rely largely on heat produced by adults to maintain a high T b, but are well able to cope with regular falls in T b of > 108C and a concomitant decrease of RMR. This thermal tolerance and reduction in energy expenditure should allow the mother to forage and replenish her own body fuels while her offspring are left alone in the nest.
D. M. Stoddart - One of the best experts on this subject based on the ideXlab platform.
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Plasma androgen, social position, and response to GnRH in the marsupial Sugar Glider Petaurus breviceps (Marsupialia: Petauridae)
Journal of Zoology, 1997Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:The effect of gonadotrophin-releasing hormone GnRH on plasma testosterone was examined in male Sugar Gliders Petaurus breviceps that were judged to occupy either the highest or lowest position in stable colonies consisting of up to four males and two females. Experiment were carried out at a time when breeding occurred in two of the three colonies, as evidenced by the presence of pouch young.
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Behavioral and endocrinological correlates of social status in the male Sugar Glider (Petaurus breviceps Marsupialia: Petauridae).
Physiology & behavior, 1994Co-Authors: J. Mallick, D. M. Stoddart, Ivor H. Jones, Adrian J. BradleyAbstract:Socially dominant male Sugar Gliders are heavier than socially subordinate males, have higher plasma testosterone and lower cortisol concentrations, win more social encounters, scan the arena more, scent-mark more, and are more active and move more quickly, even though they spend more time in the colony nesting box. When they are transferred into a foreign stable colony there is an impressive reversal of behavioral measures and a concomitant decrease in concentration of plasma testosterone and rise in cortisol that is apparent over the first 3 weeks of observation.
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The dorsal paracloacal gland and its relationship with seasonal changes in cutaneous scent gland morphology and plasma androgen in the marsupial Sugar Glider (Petaurus breviceps; Marsupialia: Petauridae)
Journal of Zoology, 1993Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:A study spanning two breeding seasons was carried out to examine changes in the size of the dorsal paracloacal glands and testes in the marsupial Sugar Glider Petaurus breviceps Waterhouse 1839. These changes were related to seasonal increases in the plasma testosterone concentration and to morphological changes in the frontal and gular cutaneous scent glands of males. Both dorsal paracloacal glands and testes underwent a seasonal cycle of development which reached its maximum during the June-September breeding season. These changes coincided with an increase in the plasma testosterone concentration and with the increase in activity of certain cell types within the frontal and gular glands. Castration caused a significant decrease in the size of the dorsal paracloacal glands, while androgen replacement was effective in restoring the glands to their pre-castration size thus demonstrating the influence of androgens upon the activity of these glands. The synchronization which exists between plasma testosterone concentration, cutaneous scent gland morphology and the size of the dorsal paracloacal glands of males, suggests that the dorsal paracloacal glands, or more likely their secretions, are important in social organization in this species.
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Seasonal changes in plasma androgens, glucocorticoids and glucocorticoid-binding proteins in the marsupial Sugar Glider Petaurus breviceps.
The Journal of endocrinology, 1992Co-Authors: Adrian J. Bradley, D. M. StoddartAbstract:An investigation spanning two breeding seasons was carried out to examine endocrine changes associated with reproduction in a wild population of the marsupial Sugar Glider Petaurus breviceps, a small arboreal gliding possum.
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The frontal and gular dermal scent organs of the marsupial Sugar Glider (Petaurus breviceps)
Journal of Zoology, 1991Co-Authors: D. M. Stoddart, Adrian J. BradleyAbstract:A study spanning two breeding seasons was carried out to examine the role of androgens in the control of the frontal and gular scent glands of the marsupial Sugar Glider Petaurus breviceps Waterhouse in a wild population. Animals were captured at monthly intervals and from these blood samples were taken and tissue biopsy samples were collected from the scent glands. Several histological parameters underwent seasonal changes which were related to changes in the plasma concentration of free plus albumin bound (‘biologically active’) testosterone. The parameters which showed significant change did so during the July-September breeding season coinciding with the peak in biologically active testosterone concentration. Castration caused a significant decrease in the nuclear diameters of gular and frontal apocrine and sebaceous gland cells, and a decrease in gular apocrine cell height. These decreases were reversed with androgen replacement therapy. The nuclear diameters of apocrine tissue cells in both scent organs are positively correlated with the plasma level of biologically active testosterone. In the gular organ, but not in the frontal organ, the depth of apocrine tissue was significantly correlated with nuclear diameter. In castration and androgen replacement studies gular apocrine tissue responded more dramatically than did frontal apocrine tissue. This suggests that the gular organ is more sensitive to testosterone than is the frontal.
