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PubMed1979

Studies on metatherian sex chromosomes. IX. Sex chromosomes of the greater glider (Marsupialia: Petauridae).

The greater glider, currently but incorrectly known as Schoinobates volans, is widely distributed in forested regions in eastern Australia. All animals studied from six different localities had 20 autosomes but there were four chromosomally distinct populations. At Royal National Park, N.S.W., all female greater gliders studied had 22 chromosomes including two large submetacentric X chromosomes with subterminal secondary constrictions in their longer arms. This form of X chromosome occurred also at Bondo State Forest, Myall Lakes and Coff's Harbour, N.S.W., and at Eidsvold, Qld. At Coomooboolaroo, Qld, the X chromosome was also a large submetacentric but a secondary constriction occurred in the shorter arm. Two chromosomally distinct types apparently occur in Royal National Park, one with XY males as in all other populations, and one with XY1Y2 males. Y or Y1, but not Y2, chromosomes were eliminated from the bone marrow in all populations but were present in spermatogonia, primary spermatocytes and cultured fibroblasts. Animals from Bondo State Forest had three or more acrocentric or metacentric supernumerary chromosomes.

Animals↗
PubMed1986

Plasma prolactin concentrations throughout lactation in the eastern quoll, Dasyurus viverrinus (Marsupialia:Dasyuridae).

Blood samples were collected throughout lactation from eight D. viverrinus, and the concentrations of prolactin in the plasma determined by an heterologous, double-antibody radioimmunoassay. For the first 45-50 days of lactation concentrations fluctuated between 2 and 80 ng/ml but were generally less than 60 ng/ml. They then increased sharply to over 120 ng/ml and greater than 200 ng/ml in some animals. Levels began to decline after 120-130 days of lactation and were less than 40 ng/ml in all animals by the time lactation had ceased, between 160 and 185 days, when the young became independent. The timing of these changes correlates well with a rapid increase in the growth rate of the young, the time at which they first relinquish the teat and remain in the nest, their first intake of solid food shortly after eruption of the first molars and specific changes in milk composition. The pattern of prolactin concentrations throughout lactation in the quoll is therefore very similar to that previously described for the tammar, Macropus eugenii, and the possum, Trichosurus vulpecula.

Animals↗
PubMed1988

Changes in milk composition during lactation in the potoroo, Potorous tridactylus (Marsupialia: Potoroinae).

Milk samples from captive potoroos were analysed for composition during weeks 3-25 of the lactation period. During pouch residence, up to week 16, carbohydrate levels were high, ranging from 9 g 100 ml-1 at week 5 to 15 g 100 ml-1 at week 15; fat levels were consistently low, at around 2 g 100 ml-1; protein levels gradually increased from 5 g 100 ml-1 before week 10 to 12 g 100 ml-1 at week 16. Growth rates during this period increased exponentially, from 1 g week-1 at week 3 to 40 g week-1 at week 16. Thereafter, as the young left the pouch, marked changes were seen in carbohydrate and fat levels: by week 25, carbohydrate levels had fallen to 2 g 100 ml-1, and fat levels had risen to 26 g 100 ml-1. Protein levels increased moderately, reaching 15 g 100 ml-1 by week 25. Growth rates further increased during this period, to reach 60 g week-1 by week 25. Thus, trends in milk composition previously observed in Macropus species were observed also in the potoroo, suggesting a consistent pattern across the macropodid family. Carbohydrate levels in potoroo milk tend to be higher than in other macropodids, but total milk intake is as important as composition in determining growth rates.

Animals↗
PubMed1988

Milk composition in the northern brown bandicoot, Isoodon macrourus (Peramelidae, Marsupialia).

Milk samples were obtained at regular intervals throughout lactation from northern brown bandicoots, Isoodon macrourus, in captivity. Total concentration of milk solids was initially 7% (w/w) and increased linearly to 45% (w/w) by 55 days. Carbohydrate, lipid and protein concentrations increased from about 2% (w/w) to about 7-8% (w/w) at 30 days. Thereafter they diverged, with lipid increasing to between 25-30% (w/w) at 56 days, protein reaching maximal values of 10-15% (w/w) at just over 40 days and carbohydrate gradually declining to about 5% (w/w) at 56 days before a rapid fall to 1-2% (w/w) at the completion of lactation. The milk of the bandicoot exhibits a similar pattern of change during the course of lactation to that shown by other marsupials.

Animals↗
PubMed1989

Luteinizing hormone in the Kowari, Dasyuroides byrnei (Marsupialia:Dasyuridae), during the oestrous cycle and pregnancy, and the effects of gonadectomy in male and female.

A heterologous double antibody radioimmunoassay has been validated for measurement of LH in plasma of a dasyurid marsupial. Basal concentrations in the oestrous cycle of female kowaris were in the range of 0.5-2.0 ng NIH-oLH-S19 mL-1. Many animals showed elevated LH concentrations (3.0-12.0 ng mL-1) between 8 and 15 days before oestrous but no pre-ovulatory surge was detected. Gonadectomy resulted in greatly increased concentrations of LH, and decreases in testosterone and progesterone concentrations in male and female respectively. In the female LH values ranged from 10-50 ng mL-1 but in the male LH values were greater than 50 ng mL-1.

Animals↗
PubMed1989

Plasma progesterone and body weight in the pregnant and non-pregnant kowari, Dasyuroides byrnei (Marsupialia:Dasyuridae).

Female kowaris are seasonal breeders (May-November) with a gestation of 32.5 +/- 1.8 days (mean +/- s.d., n = 35). The oestrus cycle including pregnancy is 59.0 +/- 6.7 days in duration (mean +/- s.d., n = 12) and is not significantly different from the non-pregnant cycle of 60.3 +/- 7.1 days (mean +/- s.d., n = 15) (P greater than 0.1). Animals maintained on a fixed diet show an increase and fall in body weight before oestrus and again at the end of the oestrous cycle or a pregnancy; these changes correlate closely with progesterone concentration. Plasma progesterone concentration and body weight were measured in six kowaris undergoing an oestrous cycle then a pregnancy in the breeding season of 1981. The basal concentration (mean +/- s.d.) of progesterone prior to the breeding season was 0.35 +/- 0.21 ng mL-1. There were mean rises of 1.84 +/- 1.1 and 2.47 +/- 1.5 ng mL-1, respectively, before the first and second oestrous periods which had declined to near basal levels by the day of oestrus. Peak values of 9.9-11.5 ng mL-1 were measured between days 23 and 30 of oestrous cycle and pregnancy. The pattern of changes in body weight and plasma progesterone concentration was similar in pregnant and non-pregnant animals but the decline in weight and progesterone occurred earlier in pregnant kowaris.

Analysis of Variance↗
PubMed1989

Influence of the immature testis on sexual differentiation in the tammar wallaby, Macropus eugenii (Macropodidae: Marsupialia).

Reproduction in the tammar wallaby, Macropus eugenii (Desmarest), is highly seasonal in the females but not the males. This study was designed to determine whether the difference is established during early life as a result of exposure to the developing testes. At day 10 after birth, when the sex can be distinguished externally, testes were removed from males and placed under the flank skin of females, while other groups of males and females were subjected to surgery without interfering with the gonads. The testis grafts remained palpable for 3-6 months. Sex-chromosome constitution was confirmed by karyotyping. At 3 years of age, the body weights and dimensions of the grafted females were not significantly different from those of the sham-operated females, whereas those of the castrated males were significantly larger and were equal to those of the sham-operated males, indicating that there is genetical control of growth independent of the testis in this species of marsupial. During 5 years of observations, none of the grafted females ever produced young, whereas all of the sham-operated females produced young each year from the second year. The grafted females had a mixture of male and female reproductive structures. The pouch and mammary glands developed normally, as did the Mullerian duct derivatives, the vaginal complex, the uteri and the oviducts. The ovaries were either devoid of oocytes and follicles or had reduced numbers, the Wolffian ducts were retained to varying degrees, the urogenital strand had developed into a prostate indistinguishable in size and structure from that of intact males, and the genital tubercle had developed into a normal-sized penis with a crus penis and Cowper's glands. In the castrated males, the scrotum developed normally and contained the gubernaculum and vas deferens. There was no evidence of Mullerian duct derivatives, and the urogenital strand was a simple canal, as in females. There were no Cowper's glands and no penis or erectile tissue. In one hemicastrated male, there was no development of the penis, although the remaining testis occupied the scrotum and showed compensatory hypertrophy. These findings indicate that the testis, at day 10, has a profound influence on the early differentiation of the Wolffian ducts, prostate and penis but cannot influence the differentiation of the Mullerian duct derivatives. The testis does not have any effect on the development of the pouch, mammary glands or scrotum or on somatic growth, all of which are apparently under independent genetical control.

Animals↗
PubMed2005

Lateralisation of escape responses in the stripe-faced dunnart, Sminthopsis macroura (Dasyuridae: Marsupialia).

Although lateralisation has been observed in many vertebrate species, marsupials have been neglected in the study of lateralisation. We investigated the behavioural responses of the stripe-faced dunnart (Sminthopsis macroura) to a mechanical model of a snake approaching into the monocular (left and right) or the binocular visual field. The snake model was presented to 30 adult subjects. The behavioural responses and the latency to react to the stimulus were scored. Reactivity was calculated by pooling scores for retreat, startle, ears back, and orientation. Retreat tended to be the most common of these responses. Approach of the snake into the dunnarts' left monocular visual field elicited a significantly higher reactivity compared to approach into the right or binocular visual field. Half of the animals did not respond in the 60 seconds allocated when the stimulus approached on their right side, whereas only seven did not respond when the stimulus approached on the left, and ten when the stimulus was presented binocularly. These results are consistent with the right hemisphere's known specialisation for controlling fear and escape responses. Our results suggest that marsupials are lateralised in a way similar to other vertebrates.

Animals↗
PubMedDate not supplied

Nitrogen requirement of the omnivorous greater bilby, Macrotis lagotis (Marsupialia: Peramelidae).

Mainly due to their utilisation of relatively low-fiber diets compared to herbivorous mammals, omnivores are expected to have correspondingly low maintenance nitrogen requirements (MNRs). The limited studies examining nitrogen requirements of omnivorous mammals to date have shown this to be the case. In this article, we determine the dietary MNR of greater bilbies (Macrotis lagotis), arid-zone omnivorous marsupials, by feeding them varying proportions of mixed seeds and dried currants (sun-dried grapes). We also examine the possibility that bilbies conserve nitrogen by recycling endogenous urea to their gastrointestinal tract. The dietary MNR of 127 mg N kg(-0.75) d(-1) calculated for the bilby falls within the range calculated for other marsupial omnivores and is lower than that of any of the herbivores. This low requirement for nitrogen was correlated with significant recycling of endogenous urea to the gut; bilbies recycled between 44% and 80% of urea synthesised in the liver, but the proportion recycled was independent of dietary nitrogen intake. The relatively low MNR of the bilby is consistent with its low rates of basal metabolism and the recycling of endogenous urea to the gut, both of which reduce urinary nitrogen losses, and a low-fiber diet that minimises metabolic fecal nitrogen loss. Because the bilby inhabits an environment where its food supply is unpredictable and of seasonally low nitrogen content, this species is likely to benefit from its low requirement for nitrogen.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

Effects of temperature on metabolism, ventilation, and oxygen extraction in the southern brown bandicoot Isoodon obesulus (Marsupialia: Peramelidae).

The effects of ambient temperatures (T(a)) from 10 degrees to 35 degrees C on metabolism, ventilation, and oxygen extraction were examined for the southern brown bandicoot (Isoodon obesulus). Oxygen consumption (VO2) followed the pattern typical for endotherms, decreasing with increasing T(a) from 10 degrees to 25 degrees C. It did not significantly change between Ta=25 degrees and 35 degrees C (the thermoneutral zone). VO2 was approximately 2.4 times higher at Ta=10 degrees C (0.967 mL O(2) g(-1) h(-1)) compared with basal (0.410 mL O(2) g(-1) h(-1)) at Ta=30 degrees C. While the metabolic rates of the bandicoots were basal at Ta=30 degrees C, respiratory frequency (f(R)) was 24.6 breaths min(-1), tidal volume (V(T)) was 7.79 mL, minute volume (V(I)) was 191.3 mL min(-1), and oxygen extraction efficiency (EO2) was 26.8%. Increased VO2 at Ta< or =25 degrees C was associated with a large increase in V(I) due to increases in V(T) and f(R). A greater proportion of the change was due to the increase in tidal volume. EO2 was constant at approximately 26% for all T(a) up to and including 30 degrees C. At Ta=35 degrees C, EO2 decreased to 17.7%, f(R) increased to 35.6 breaths min(-1), and V(T) decreased to 7.22 mL. The metabolic and ventilatory physiology of the southern brown bandicoot are typical of an unspecialized medium-sized marsupial.

Animals↗
PubMedDate not supplied

Spermatogenesis and synaptonemal complexes of hybrid Petrogale (Marsupialia).

Fertility, synaptonemal complexes (SCs) and spermiogenesis were examined in hybrids bred from four chromosomally different species of rock wallaby. Each of the four male hybrids had different forms of chromosomal heterozygosity (i.e., a trivalent, a quadrivalent, a pentavalent, and a trivalent plus two centric shifts). Testes and seminiferous tubules of each hybrid were smaller than those of full-bloods, and no hybrid produced young when paired with parous females. The degree of chromosomal heterozygosity in the hybrids was associated with the degrees of asynapsis, XY-autosome associations, and disruption of spermatogenesis. In only one hybrid were all stages of spermiogenesis commonly seen, and in this animal, sperm abnormalities were common. SC formation was consistent with that expected from the G-banded karyotypes, except that in one hybrid the chromosomes involved in the presumed centric shifts did not pair as expected but instead formed heteropycnotic masses. In addition, the studies demonstrated the links between the nonpairing X and Y chromosome and revealed an array of patterns of abnormalities at the ultrastructural level in spermiogenesis of hybrid marsupials.

Animals↗
PubMed1975

Communication in the tasmanian devil (Sarcophilus barrisii) and a survey of auditory communication in the marsupialia.

The female-male interaction system of the Tasmanian devil, Sarcophilus barrisii, was analyzed in captivity. A description of visual, chemical, tactile, and auditory signals was prepared based on an encounter series. The vocalizations of the Tasmanian devil were classified and described with respect to their probable function. The vocalizations of other marsupials are compared with those of the Tasmanian devil. Four basic syllable types are defined. Although the auditory signals of marsupials are generally low in intensity and easily overlooked by an investigator, it would appear that they exhibit a complexity equivalent to the calls of many Eutherian mammals. Marsupial vocalizations are not necessarily always produced in specific contexts, but the four basic vocalization types are related to at least four different functions and reflect adaptations for conveying information in several widely differing contexts. The problems of establishing homologies among vocalizations are discussed.

Agonistic Behavior↗
PubMed1986

Cytogenetic analysis of some Brazilian marsupials (Didelphidae: Marsupialia).

Three species of marsupials from the Amazon region (Marmosa cinerea, Caluromys lanatus, and Didelphis marsupialis) and two from the region of São Paulo (Didelphis marsupialis and Didelphis albiventris) were studied. The G-banding pattern of the species with 2n = 14 (M. cinerea and C. lanatus) was very similar, as well as the pattern of G-bands in the species with 22 chromosomes (Didelphis). All of the autosomes of M. cinerea and D. albiventris have centromeric C-bands and the Y chromosome is totally C-band positive. The long arm of the M. cinerea X chromosome is completely C-band positive except for a negative band close to the centromeric region. In D. albiventris the long arm of the X chromosome is C-band positive except for a negative band close to the telomeric region. In M. cinerea the silver-stained nucleolar organizer regions (Ag-NORs) are found in the acrocentric chromosomes, being located in the telomeric region of one pair and in the centromeric region of the other pair. Caluromys lanatus has centromeric Ag-NORs in one acrocentric and in one submetacentric chromosome pairs. Didelphis marsupialis has three chromosome pairs with telomeric Ag-NORs. In D. albiventris the Ag-NORs are terminal and located in both arms of one pair and in the long arm of two pairs of chromosomes.

Animals↗
PubMed1989

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). II. G-banding analysis of Petrogale godmani.

Chromosomal rearrangements in the two currently recognised races of Petrogale godmani were examined using C- and G-banding. The nominate race P. godmani godmani (2n = 20) was found to possess an inverted chromosome 5 and an acrocentric 6-10 fusion, which can be derived from a 6-10 centric fusion by a centromeric transposition. The Cape York race (2n = 22) was found to retain the ancestral submetacentric chromosome 4 and the ancestral chromosome 5. Thus despite their genic similarity, the two races clearly have major chromosomal differences and should be regarded as separate species. Petrogale g. godmani shares two derived chromosomes with another Queensland taxon, the assimilis race of P. assimilis, indicating recent common ancestry. The Cape York race retains characteristics of an ancestral stock of Petrogale and its genic similarity with P. g. godmani could therefore be the result of extensive introgression.

Animals↗
PubMed1993

Chromosomal rearrangements in rock wallabies, Petrogale (Marsupialia: Macropodidae). VIII. An investigation of the nonrandom nature of karyotypic change.

Although the nonrandom nature of many chromosome breaks is well known, few studies have investigated the potential significance of this breakage specificity in chromosome evolution. The macropod genus Petrogale is an ideal group in which to investigate this phenomenon, since it comprises a large number of chromosomal forms, many of which appear to have differentiated relatively recently. By exposing Petrogale cells to mutagenic agents it should be possible to compare the distribution and abundance of induced breaks with those that are known to have occurred in vivo during the chromosomal differentiation of the genus. In this study, breaks were induced in mitotic chromosomes from P. assimilis and P. mareeba by exposing synchronized cultured fibroblasts to low doses of gamma radiation. The results were remarkably similar for both species and the distribution of breaks among the chromosomes appeared to be nonrandom. It was found that chromosomes 5, 6, and (possibly) 10 had a substantially higher rate of breakage than expected. These are also the chromosomes that occur disproportionately among the rearrangements identified in Petrogale. While the distribution of breaks along the chromosome appeared uniform or normal for most chromosomes, a putative "hot spot" was identified near the centromere in chromosome 5 of P. mareeba and in a homologous position near the telomere of chromosome 5 in P. assimilis. In a further experiment, a 1- to 2-h pulse of mitomycin C was used to induce centric fusions in cultured fibroblasts of P. penicillata (2n = 22); 2408 cells were examined and 112 fusions were identified. While it was found that all chromosomes participated in forming fusions, chromosome 10 was found to be most frequently involved, being present in 28.6% of the identified fusions. This frequency is far greater than would be expected if fusions were to occur at random (10%). It is significant then that chromosome 10 has been involved in five of the eight centric fusions that have been identified in Petrogale and that it is also the chromosome that has been most frequently rearranged in Petrogale. These results suggest that features of the karyotype may influence the distribution and frequency of chromosome breaks and therefore the rate and nature of chromosome evolution.

Animals↗
PubMed1996

Alpha-adrenergic stimulation of thermogenesis in a rat kangaroo (Marsupialia, Bettongia gaimardi).

The Tasmanian bettong (Bettongia gaimardi) is a small rat kangaroo without detectable brown adipose tissue (BAT). In view of our previous findings of norepinephrine-mediated increase in O2 consumption (Vo2) in the perfused hindlimb of this species, the present study examined the effect of alpha-adrenoceptors on the thermogenesis of conscious bettongs at rest by infusing adrenergic agents via an indwelling catheter in the tail vein. The resting Vo2 was 22.9 +/- 1.9 mmol.kg-1.h-1. Norepinephrine (10-80 micrograms.kg-1.min-1) stimulated Vo2 in a dose-dependent manner with the maximal increment of 46.7%. Naphazoline (an alpha 1,alpha 2-adrenergic agonist) and phenylephrine (an alpha 1-adrenergic agonist) also elicited increases in Vo2 with maximal values of 29.6 and 34.8%, respectively. In contrast, the alpha 2-adrenergic agonist clonidine had no significant effects. Both alpha- and beta-adrenergic blockers were used to antagonize the submaximal increase in Vo2 elicited by norepinephrine. As a dose of 10 micrograms.kg-1.min-1, the alpha-adrenergic blocker phentolamine abolished the effects of naphazoline and phenylephrine and reduced norepinephrine-induced Vo2 by 45.5%. The beta-adrenergic blocker propranolol inhibited the norepinephrine-induced Vo2 by 58.8% at 20 micrograms.kg-1.min-1. A combination of the two antagonists blocked 82.5% of the norepinephrine-induced Vo2. Pretreatment of the animal with indomethacin (1 mg/kg), a known inhibitor of prostaglandin cyclooxygenase, had no effect on phenylephrine-elicited Vo2. Taken together, these results indicate that alpha 1-adrenoceptors are directly involved in norepinephrine-induced thermogenesis in non-BAT tissue(s).

Adrenergic alpha-Agonists↗
PubMed1997

Feeding patterns of S. crassicaudata (Marsupialia:Dasyuridae): role of gender, photoperiod, and fat stores.

Little is known about feeding regulation in marsupials. Sminthopsis crassicaudata is a small nocturnal marsupial, whose tail contains approximately 25% total body fat. We have characterized the effect of gender, photoperiod, food deprivation, and tail removal (lipectomy) on food intake in S. crassicaudata. Males and females maintained in captivity on long-day (LD, 16:8-h light-dark cycle) and short-day (SD, 9:15-h light-dark cycle) light regimens were studied. Feeding patterns under LD and SD photoperiods were initially measured under conditions of ad libitum food supply and then in groups of animals exposed to 24- and 36-h periods of food deprivation. Feeding occurred predominantly in the dark. Females maintained on SD photoperiods for 5 wk ate less (P < 0.005) than females on LD or males on either SD or LD, but this reduction in food intake was not associated with a decrease either in body weight or tail width. After both 24- and 36-h fasts, total food intake in the subsequent 24 h increased (P < 0.001) up to 100% in all groups, with no gender or photoperiod effect. SD females, however, ate less (P < 0.05) than LD females in the first 6 h after refeeding. Tail width decreased (P < 0.05) in all groups of animals after the 36-h fast but only in LD animals after the 24-h fast (P < 0.05). Body weight decreased similarly in all groups of animals after fasting. The effect of tail removal was studied in LD males. The procedure, which was well tolerated, resulted in an initial decrease in body weight (P < 0.005), which recovered within 3 wk. On day 45 in the animals whose tails were removed, body fat was approximately 30% greater than body fat of controls (P < 0.02). No significant increase in food intake occurred after tail removal. These data demonstrate in Sminthopsis crassicaudata 1) a photoperiod and gender-dependent effect on food intake, 2) the ability to regulate the amount and distribution of total body fat, and 3) a dissociation between the regulation of food intake and changes in body fat stores, which suggest alterations in energy expenditure.

Adipose Tissue↗