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PubMed1986

Reproduction in the male honey possum (Tarsipes rostratus: Marsupialia): the epididymis.

The epididymis of the adult honey possum, Tarsipes rostratus, is enclosed by a heavily pigmented tunica vaginalis and lies with the testis in a prominent prepenile scrotum. It is connected to the testis by a single ductus efferentis and is lined by approximately equal numbers of cuboidal ciliated and principal cells. It is unusual for marsupials in having no well-defined compartments or fibrous septae and in having extensive convolutions of the duct only at the caudal flexure. Three principal functional zones (initial, middle, and terminal segments) were identified in the epididymis, based on epithelial type and ultrastructural evidence of sperm maturation. Luminal diameter increases progressively throughout the tract, and epithelial height variations (from about 2 to 20 microns) are greatest in the terminal segment. The epithelium itself is remarkably low (maximum of 21.6 microns) compared with that seen in the epididymis of other mammals. The thickness of the peritubular smooth muscle coat increases close to the junction of the epididymis and ductus deferens. Sperm concentrations were estimated from counts of sperm nuclei and thus can be no more than approximations. The figures are consistent, however, with a rapid increase in concentration in the initial segment, indicating extensive fluid resorption. Sperm concentrations appear to peak in the distal zone of the terminal segment, although sampling problems and wide variations in count make such a conclusion only tentative. Principal and basal cells are the predominant cell types in the epididymal epithelium. Basal cells are most abundant in the initial and distal middle segment. Principal cells show structural evidence of active exchange with the luminal contents and have abundant apical stereocilia, the structure of which depends on the epididymal zone. Other cell types occur less commonly in the epithelium. Lipid-rich and phagocytic principal cells are restricted to the middle and distal zones of the middle segment, respectively. Clear cells, restricted to the terminal segment, and halo cells were found in very low numbers. As in some other marsupials, principal cells (possibly specialized for this function) selectively remove cytoplasmic droplets and probably other cellular debris from the luminal contents. In Tarsipes, however, this process is not very efficient, and many discarded droplets pass through to the terminal segment where they form large masses of debris associated with aggregates of degenerating spermatozoa.

Animals↗
PubMed1995

Cephalic morphology of the honey possum, Tarsipes rostratus (Marsupialia: Tarsipedidae); an obligate nectarivore.

The sharply tapering skull of the honey possum is delicately constructed and has only a few, minute teeth; its mandible is reduced to a thin, flexible rod. The mandibular fossa has been displaced caudally to the caudomedial corner of the squamosal. Head skeletons of the feathertail glider and western pygmy-possum, omnivores that are closely related to the honey possum, bear greater resemblance to the distantly related carnivorous fat-tailed dunnart than to the honey possum. Selected muscles associated with the jaws, hyoid, and tongue of these four mouse-sized (9-22 g) marsupials are described for the first time. The honey possum is characterized by a greatly reduced temporalis that is almost completely hidden by the eye. Its digastric consists of a single belly that inserts onto the caudal margin of the mylohyoid. The lateral pterygoid is relatively long as it extends caudally to insert onto the elongated mandible. The stylohyoid originates high up on the caudal surface of the tympanic bulla; it curves around the caudal and ventral surfaces of the bulla to reach the basihyoid. The insertion of the genioglossus is restricted to the caudal quarter of the tongue. Homologous muscles of the feathertail glider and western pygmy-possum are more similar to those of the fat-tailed dunnart. In addition to the very different musculoskeletal system, the honey possum has an unusual tongue that tapers to a fine point.

Animals↗
PubMed1996

Circulating levels of prolactin and progesterone in a wild population of red kangaroos (Macropus rufus) Marsupialia: Macropodidae.

Circulating progesterone and prolactin levels were measured in shot and live-caught wild red kangaroos using radioimmunoassays validated for the red kangaroo. The objective of the study was to correlate hormone profiles with reproductive status and determine if red kangaroos follow the general pattern elucidated for other macropodids. During Phase 2a lactation ( < 70 days) plasma progesterone concentrations were < 189 pg/ml (n = 41). This value increased to > 600 pg/ml (n = 32) during the transition to Phase 3 lactation (181 to 235 days) when the quiescent corpus luteum and embryo were reactivated. Progesterone concentrations then decreased to < 300 pg/ml (n = 29) during dual lactation when females were suckling a neonate and a young at foot. Concentrations of prolactin during Phase 2a were < 6 ng/ml (n = 17). Coincident with the period of reactivation of the diapausing blastocyst (181 to 235 days), plasma prolactin concentrations increased to 15 ng/ml (n = 32), then decreased and remained low through the subsequent stage of dual lactation. These results indicate that progesterone and prolactin profiles in wild red kangaroos follow patterns found previously in other macropodid species, the tammar and Bennett's wallabies.

Animals↗
PubMed1993

Differentiation of the gonads and initiation of mammary gland and scrotum development in the brushtail possum Trichosurus vulpecula (Marsupialia).

The first appearance of the mammary and scrotal primordia and the sexual differentiation of the gonads of the brushtail possum, Trichosurus vulpecula, are described. Primordial germ cells were first observed, in fetuses of 7.5 mm crown-rump length, in the gonadal ridges and migrating up the dorsal mesentery. Mammary primordia were first observed in fetuses of 11 mm, and scrotal primordia in those of 12 mm crown-rump length. These structures were diagnostic of female and male brushtail possums respectively. Processus vaginales and gubernacula showed sexual dimorphism, being better developed and appearing earlier in males than in females. Sexual differentiation of the gonads occurred after the appearance of mammary and scrotal primordia, the testes being first recognisable in a 14.5-mm fetus and the ovaries postnatally. Birth occurred between the stages of 14 and 15 mm crown-rump length. These observations appear to indicate that the development of mammary and scrotal primordia are not under gonadal hormonal control, but under direct genetic control, as suggested for the tammar wallaby by previous authors.

Animals↗
PubMed1976

Ultrastructural changes in spermatozoa of the brush-tailed possum, Trichosurus vulpecula (Marsupialia), during epididymal transit. Part II: The acrosome.

The acrosome in spermatozoa from the caput epididymidis of the Australian Brush-tailed possum, Trichosurus vulpecula, typically forms a cup-like structure, sitting on the anterior third of the dorsal surface of the nucleus. The base of the acrosomal 'cup' is narrowly separated from the nuclear surface, while the body of the 'cup' projects voluminously away from the nucleus. During epididymal transit these pronounced marginal extensions of the acrosome are retracted towards the nucleus, and the electron dense acrosomal material undergoes a process of compaction within the plasma membrane of the head to produce the convex ovate form of the definitive acrosome. During this process a variety of bizarre forms of the acrosome are produced before its final configuration is attained.

Acrosome↗
PubMed1976

Spermiogenesis in the brush-tailed possum, Trichosurus vulpecula (Marsupialia). The development of the acrosome.

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.

Acrosome↗
PubMed1975

Ultrastructural changes in spermatozoa of the brush-tailed possum, Trichosurus vulpecula (Marsupialia), during epididymal transit. Part I: The flagellum.

During epididymal transit, a fibre network and an array of vesicles develop in the posterior two-thirds of the midpiece in sperm of the Brush-tailed possum, Trichosurus vulpecula. The fibre network is developed by the time the sperm reach the corpus epididymidis, and is composed of evenly spaced, helically arranged fibres lying immediately beneath the plasma membrane. The angle of these fibrous helices is always counter to that of the underlying mitochondrial helix. Separating the fibre network from the mitochondria is a layer of granular material which develops at the same time, and over the same length of the midpiece as the fibre network. A somewhat tenuous fibre network is found between the fibrous sheath and plasma membrane in the anterior principal piece of sperm from all regions of the epididymis. The array of vesicles is developed by the time sperm reach the cauda epididymidis. The vesicles resemble pinocytotic vesicles; some appear as invaginations of the plasma membrane, and are open to the medium surrounding the spermatozoon by a narrow neck, while others are entirely enclosed within the spermatozoon, and lie at varying distances between the plasma membrane and the layer of granular material.

Animals↗
PubMed1992

Mast cell types in the lymph nodes of the opossum Didelphis albiventris (Marsupialia, Didelphidae).

Using histological and histochemical techniques, we have found a unique population of mast cells in the lymphatic sinuses of lymph nodes from different anatomical regions of the opossum. The lymphatic-sinus mast cells of the medullary sinuses were numerous, and could be easily distinguished from the connective-tissue mast cells of the dermis and lymph node capsule by their larger size and their enlarged cytoplasmic granules that were also more heterogeneous in shape and staining properties.

Animals↗
PubMed1995

Exon organization and sequence of the genes encoding alpha-lactalbumin and beta-lactoglobulin from the tammar wallaby (Macropodidae, Marsupialia).

Clones encompassing the genes encoding alpha-lactalbumin and beta-lactoglobulin were isolated from a tammar wallaby genomic library, the exons localized using end-labeled oligonucleotides and the DNA sequences determined. The tammar beta-lactoglobulin gene has the same 7 exon-6 intron structure as the sheep homologue. Potential binding sites for mammary gland-specific transcription factors were identified, on the basis of similarity to sites in the sheep gene, in the promoter region of the tammar beta-lactoglobulin gene. The tammar gene encoding alpha-lactalbumin appears to contain four introns rather than three as are present in the eutherian homologues, or the evolutionarily related lysozyme gene. The additional intron appears to occur within the 5' noncoding region of the tammar gene.

Amino Acid Sequence↗
PubMed1987

Digestion and metabolism of high-tannin Eucalyptus foliage by the brushtail possum (Trichosurus vulpecula) (Marsupialia: Phalangeridae).

The digestion and metabolism of Eucalyptus melliodora foliage was studied in captive brushtail possums (Trichosurus vulpecula). The foliage was low in nitrogen and silica but high in lignified fibre and phenolics compared with diets consumed by most other herbivores. The high lignin content was suggested as the main cause of the low digestibility of E. melliodora cell walls (24%); microscopic observations of plant fragments in the caecum and faeces revealed few bacteria attached to lignified tissues. The conversion of digestible energy (0.34 MJ X kg-0.75 X d-1) to metabolizable energy (0.26 MJ X kg-0.75 X d-1) was low compared to most other herbivores, probably because of excretion of metabolites of leaf essential oils and phenolics in the urine. When the inhibitory effect of leaf tannins on fibre digestion was blocked by supplementing the animals with polyethylene glycol (PEG), intake of dry matter, metabolizable energy and digestible fibre increased. These effects were attributed to the reversal by PEG of tannin-microbial enzyme complexes. It was concluded that the gut-filling effect of a bulk of indigestible fibre is a major reason why the brushtail possum does not feed exclusively on Eucalyptus foliage in the wild.

Animals↗
PubMed1992

Enkephalin- and serotonin-like immunoreactivity in the aortico-pulmonary paraganglia of the white-belly opossum Didelphis albiventris (Marsupialia).

Serial histological sections of the interatrial septum and basal heart vessels of the weaned and juvenile white-belly opossum (Didelphis albiventris) were obtained in order to study the presence of paraganglia and their content of regulatory peptides and serotonin. Paraganglion groups were mapped between the aorta and pulmonary arteries and close to the bifurcation of the pulmonary trunk and were found to contain cells with immunoreactivity to serotonin and to the neuroendocrine markers PGP 9.5 and NSE. When these paraganglia were tested for immunoreactivity to a battery of regulatory peptides, all were found to be positive for methionine-enkephalin, leucine-enkephalin and galanin. The hypothesis is raised that these peptides and serotonin, besides catecholamines, produced by these paraganglia may play a physiological role in the functions of the cardiovascular system of the white-belly opossum.

Animals↗
PubMed1998

Phylogenetic analysis of three lipocalin-like proteins present in the milk of Trichosurus vulpecula (Phalangeridae, Marsupialia).

Three proteins have been identified in the milk of the common brush tail possum. Trichosurus vulpecula that from sequence analysis are members of the lipocalin family. They include beta-lactoglobulin, which appears to have two forms; a homologue to the late-lactation protein found in tammar, Macropus eugenii; milk; and a novel protein termed trichosurin. Whereas beta-lactoglobulin and trichosurin are both expressed throughout lactation, the late-lactation protein is not detected in samples taken before days 100-110 of lactation. The cDNAs encoding each of these proteins have been isolated from cDNA libraries prepared using possum mammary mRNA and sequenced. Phylogenetic analysis showed that the T. vulpecula beta-lactoglobulin, along with two other macropod beta-lactoglobulins, forms a subclass of beta-lactoglobulins distinct from those for eutherian mammals; both marsupial late-lactation proteins appear to have similarities to a family of odorant-binding proteins, whereas trichosurin has similarities to the major urinary proteins of rodents.

Amino Acid Sequence↗
PubMed2003

Milk composition and growth in wild and captive Tasmanian bettongs, Bettongia gaimardi (Marsupialia).

Changes in milk composition (total solids, carbohydrate, protein, lipid and calculated gross energy content) during lactation in three groups of Tasmanian bettongs ( Bettongia gaimardi): free-living animals (wild group), captive animals offered a diet of dry dog food and apples ad libitum (ad lib group), and captive animals fed restricted amounts of the same diet (maintenance group) were related to growth rates (measured as body mass and head length) of their young. There were no significant differences in the concentration of milk solids among the three groups, but the wild group had higher lipid concentrations and the maintenance group had higher carbohydrate but lower protein concentrations. For all three groups, milk total solids increased through lactation from ca. 25% to ca. 45% and carbohydrate concentrations decreased from ca. 18% to about 3%. Protein concentrations increased from ca. 5% to ca. 10% in the wild and ad lib groups, but only from 4% to 8% in the maintenance group. Lipid concentrations increased in the wild and ad lib groups from ca. 4% to ca. 18%, but in the maintenance group only to ca. 7%. Calculated gross energy content of milk increased through lactation in the wild and ad lib groups (from ca. 500 kJ.100 ml(-1) to ca. 1,000 kJ.100 ml(-1)), but there was no significant increase in the maintenance group. The volume of milk produced increased to a peak just prior to permanent pouch vacation by the young, when the gross energy output in milk was 120-150 kJ.3 h(-1) in the wild and ad lib groups. On a daily basis this is equivalent to the milk energy output of larger wallabies, and helps to explain the relatively high growth rates of young Tasmanian bettongs. There were significant differences in growth rates among the groups, with the heaviest young always in the ad lib group. Thus differences in milk composition resulting from different planes of nutrition can lead to differences in growth rates of marsupial young.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Localization of chromosome regions in potoroo nuclei ( Potorous tridactylus Marsupialia: Potoroinae).

Chromosome paints of the rat kangaroo ( Aepyprymnus rufuscens, 2 n=32) were used to define chromosome regions in the long nosed potoroo ( Potorous tridactylus, 2 n=12 female, 13 male) karyotype and localize these regions in three-dimensionally preserved nuclei of the potoroo to test the hypothesis that marsupial chromosomes have a radial distribution. In human nuclei chromosomes are distributed in a proposed radial fashion. Gene-rich chromosomes in the human interphase nucleus are preferentially located in the central area while gene-poor chromosomes are found more at the periphery of the nucleus; this feature is conserved in primates and chicken. Chromosome ordering in nuclei of P. tridactylus is related to their size and centromere position. Its relationship with replication patterns in interphase nuclei and metaphase was studied. In addition it was observed that the nucleus was not a smooth entity but had projections occupied by specific chromosome regions.

Animals↗
PubMed1990

Zoogeography and host associations of the Heterodoxus octoseriatus group and H. ampullatus (Phthiraptera: Boopiidae) from rock-wallabies (Marsupialia: Petrogale).

Species of the Heterodoxus octoseriatus group infest five species, comprising eight chromosome races, of Petrogale in Queensland and northern New South Wales, Australia. The precise host and geographic ranges of the 11 species of the H. octoseriatus group were determined. Individual hosts and host populations were infested by single species of lice only. The geographic ranges of lice were discrete. In some cases the geographic ranges of louse species and their hosts were approximately congruent. In others they were completely incongruent and it was unclear which species originally infested which hosts or even which was the most recent colonizer. In at least one case, expansion of the geographic range of one species of louse apparently led to fragmentation of the range of another and subsequently, to allopatric speciation.

Animals↗
PubMed1993

Blood O2 transport and Hb types in the embryonic Tammar Wallaby (Marsupialia, Macropus eugenii).

Blood oxygen transport and hemoglobin type have been studied in the developing Tammar Wallaby from 20 days gestation, just after the circulation first forms, until 28 days gestation, 2 days after birth. The oxygen equilibrium curves (OECs) of the embryonic whole blood had high P50 values, mean being 44.6 mmHg at 36 degrees C, PCO2 = 40 mmHg. In contrast to other viviparous species studied, the embryonic OECs were well to the right of the maternal OEC. There was no significant change in P50 throughout the age range studied. The curves had high Hill coefficients above about 50% saturation (mean = 5.65), indicating cooperativity between hemoglobin tetramers. The Bohr effect (measured as delta log P50/delta log PCO2) was low, about half that of the adult. The early embryos (days 20 and 21) had only 2 or 3 Hb types, with the other embryonic Hbs appearing by 22 days of gestation. The proportion of the four embryonic Hbs changed during development although one type was always predominant (> 45%). This is the first serial study of blood O2 carriage and Hb type in developing marsupial embryos. The finding of a right-shifted embryonic OEC throughout intrauterine development suggests that, contrary to current belief, a right-shifted curve may be physiologically advantageous to a developing embryo.

Age Factors↗
PubMed1981

The opossum, Didelphis marsupialis (Marsupialia: Didelphidae), as a reservoir host of Leishmania braziliensis guyanensis in the Amazon Basin of Brazil.

A total of 52 opossums (six species) were examined for evidence of infection with Leishmania in three different areas of forest near Manaus, Amazonas State, Brazil. No infections were detected in 27 opossums from a region of relatively undisturbed forest, including specimens of Didelphis marsupialis (18); Metachirus nudicaudatus (four); Monodelphis brevicaudata (one); Marmosa cinerea (two); M. murina (one) and M. parvidens (one). Of 15 D. marsupialis captured from a biological reserve, much disturbed by man, three were infected with L. braziliensis guyanensis: isolations were made from the skin of two of the animals, and from the viscera of the third. The isolates were biologically and biochemically indistinguishable from one isolate of L. b. guyanensis made from man and two from the sandfly vector Lutzomyia umbratilis from the same area. Two of eight D. marsupialis and both of two M. cinerea from another area of virgin forest used for army manoeuvres were infected with Leishmania mexicana amazonensis: the parasite was in all four cases isolated from normal skin. Five of nine specimens of Proechimys guyannensis, from the vicinity of Manaus, were also infected with L. m. amazonensis. A further 13 mammals (eight species) were negative for Leishmania. The importance of opossums as a reservoir of L. b. guyanensis is discussed. Although they may play only a minor role in virgin forest which is undisturbed by man, opossums (D. marsupialis) may become a significant reservoir of infection where man's activities have eliminated the major reservoir--which has yet to be incriminated.

Animals↗