Genetically-Determined Variation of Pelage Color and Reflectance in Natural and Laboratory Populations of the Marsupial Sminthopsis-Crassicaudata (Gould)

A study of variation in dorsal pelage colour and reflectance of the dasyurid marsupial, Sminthopsis crassicaudata, has been based on animals captured from widely scattered areas in south-central Australia, and on a laboratory colony of this species. Measurements on the degree of resemblance between relatives gave heritability estimates of pelage reflectance close to the theoretical upper limit of unity. Measurements on the reflectance of animals captured from the wild revealed a geographical cline, with reflectance decreasing (animals becoming darker) with increasing southerly latitude. The higher reflectance (paler coloured) animals were found to inhabit the northern desert areas. We suggest that this cline results from a selective advantage enjoyed by animals whose dorsal pelage colour makes them relatively inconspicuous in their habitat to nocturnal preditors.

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Constraints on the Proterozoic supercontinent cycle from the structural evolution of the south-central Musgrave Province, central Australia

Precambrian Research ◽

10.1016/j.precamres.2008.10.006 ◽

2009 ◽

Vol 168 (3-4) ◽

pp. 284-300 ◽

Cited By ~ 23

Author(s):

A AITKEN ◽

P BETTS

Keyword(s):

Structural Evolution ◽

The South ◽

South Central ◽

Central Australia ◽

Supercontinent Cycle

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Ion microprobe U–Pb ages for Neoproterozoic basaltic magmatism in south-central Australia and implications for the breakup of Rodinia

Precambrian Research ◽

10.1016/s0301-9268(97)00072-7 ◽

1998 ◽

Vol 87 (3-4) ◽

pp. 135-159 ◽

Cited By ~ 269

Author(s):

Michael T.D Wingate ◽

Ian H Campbell ◽

William Compston ◽

George M Gibson

Keyword(s):

Ion Microprobe ◽

South Central ◽

Basaltic Magmatism ◽

Central Australia

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Reproductive and Genetic-Studies With a Laboratory Colony of the Dasyurid Marsupial Sminthopsis-Crassicaudata

Australian Journal of Zoology ◽

10.1071/zo9890207 ◽

1989 ◽

Vol 37 (3) ◽

pp. 207 ◽

Cited By ~ 23

Author(s):

JH Bennett ◽

WG Breed ◽

DL Hayman ◽

RM Hope

Keyword(s):

Reproductive Biology ◽

Meiotic Chromosome ◽

Litter Production ◽

Genetic Studies ◽

Adult Weight ◽

Sminthopsis Crassicaudata ◽

Laboratory Colony ◽

Marked Disparity ◽

Marsupial Species ◽

High Level

The fat-tailed dunnart, Sminthopsis crassicaudata, is a small insectivorous dasyurid (adult weight about 16 g) widely distributed in Australia. A laboratory colony of this marsupial, which has been built up over many years, is providing material for studies of dasyurid reproductive biology and genetics. In the area of reproductive biology, we have found a marked disparity in the age of maturation between the two sexes, and we are currently studying certain aspects of spermatogenesis, sperm transport, fertilisation and early embryonic development. Genetical studies have revealed large differences between the sexes in autosomal linkage values and meiotic chromosome behaviour. In females, we have observed very limited intrachromosomal recombination and this is reflected in the distal localisation of chiasmata on the autosomes. Extreme localisation of chiasmata has not hitherto been found in a mammal, and it will be interesting to see how widely it occurs in other marsupial species. The genetical and cytological findings lead to a number of predictions that are being tested in further experimental work with the colony. Although we have been able to raise litter production to a high level, the very variable and unpredictable nature of male reproductive performance currently limits the wider use of the S. crassicaudata colony. It is clear, however, that this dasyurid has the potential to become a very useful laboratory marsupial and that it will be especially valuable for comparative biomedical studies.

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GENE CONTROL OF HEMATOPOIESIS

Journal of Experimental Medicine ◽

10.1084/jem.129.5.1013 ◽

1969 ◽

Vol 129 (5) ◽

pp. 1013-1027 ◽

Cited By ~ 57

Author(s):

Beatrice Mintz ◽

Joy Palm

Keyword(s):

Experimental Studies ◽

Circulatory System ◽

Cell Types ◽

Selective Advantage ◽

Individual Variability ◽

Gene Control ◽

Control Mechanisms ◽

Red Cell ◽

Cell Strains ◽

Genetically Determined

Erythropoietic cells of two unrelated strains, C3H (or C3Hf) and C57BL/6, can coexist throughout hematopoiesis in allophenic mice experimentally produced from aggregated, undifferentiated blastomeres of separate genotypes. The presence of two red cell genotypes in these circumstances signifies that the erythroid population must normally be multiclonal, i.e., derived mitotically from at least two genetically determined cells. The two strains were detected by hemagglutination and absorption tests of erythrocytes for the specific histocompatibility antigens dictated by the H-2k and H-2b alleles. Of 34 C3H(f) ↔ C57BL/6 allophenics tested, 16 had both red cell types; the remaining 18 showed only C3H or C57 red cells and included 12 mice with both cell strains present in some other tissues. All animals with evidence of two H-2 phenotypes among circulating erythrocytes were permanently immunologically tolerant of both antigenic types and remained free of runt disease. They lived a full lifespan, up to 2 yr 7½ months of age. The data suggest a possible specific selective advantage of C57BL/6 over C3H erythropoietic tissue. There is considerable individual variability, not only in proportions of antigenically distinct erythrocytes, but also in strain composition of other tissues in the same animals. A broad spectrum of distinctive situations is found, in which parameters are varied within or outside of the circulatory system. Allophenic mice can therefore serve as investigative tools for entirely new kinds of experimental studies of gene control mechanisms and blood physiology in normal hematopoiesis and in a number of hereditary blood diseases.

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PUBLIC HEALTH, NURSING AND MEDICAL SOCIAL WORK

PEDIATRICS ◽

10.1542/peds.15.6.771 ◽

1955 ◽

Vol 15 (6) ◽

pp. 771-774

Author(s):

Charles U. Lowe

Keyword(s):

Public Health ◽

Social Work ◽

Central Asia ◽

Broad Band ◽

Medical Social Work ◽

South Central ◽

Surface Transportation ◽

Hindu Kush ◽

Desert Areas ◽

Health Nursing

Afghanistan is a country in south central Asia, approximately rectangular in shape, with an area estimated at 250,000 square miles. Its borders have been inadequately surveyed and many sections are as yet unvisited by foreigners. The Hindu Kush Mountains divide it roughly from northeast to southwest; they make surface transportation slow and difficult, and along with the desert areas of the southwest sector, reduce the tillable land to less than 20,000 square miles. In spite of this, Afghanistan raises more than enough food to feed its Population and has sufficient surplus to export. Its climate is hot in the summer and very cold in the winter, while rainfall is scarce, rarely averaging more than 11 inches Per year. Racially, 5 ethnic groups make up its population. In the east, and along the Pakistan border, one finds the Pathans. These are tall, frequently fair individuals, claiming descent from both the Greek legions of Alexander and the ancient tribes of Israel. In a broad band running mainly along the Russian border and the Oxus River are the Turkmen, herdsmen and breeders of karakul sheep. South of these, and inhabiting the center of the country from Kabul to Meshed in Persia live the Hazaris, descendents from Genghis Kahn's slaughtering hordes.

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Evidence of the establishment of Cotesia flavipes (Hymenoptera: Braconidae) in continental Africa

Bulletin of Entomological Research ◽

10.1017/s0007485300033022 ◽

1995 ◽

Vol 85 (4) ◽

pp. 525-530 ◽

Cited By ~ 35

Author(s):

C.O. Omwega ◽

S.W. Kimani ◽

W.A. Overholt ◽

C.K.P.O. Ogol

Keyword(s):

Biological Control ◽

Indian Ocean ◽

Morphological Characters ◽

Cotesia Flavipes ◽

Stem Borers ◽

Western Kenya ◽

Laboratory Colony ◽

Laboratory Populations ◽

The Indian Ocean ◽

Ocean Islands

AbstractCotesia flavipes Cameron has been released several times in Africa for biological control of gramineous stem borers. Establishment has been reported on the Indian Ocean islands of Mauritius, Réunion and Madagascar, however, several attempts to introduce C. flavipes into continental Africa are reported to have failed. Recently, several cocoon masses of C. flavipes were recovered from south-western Kenya where the parasitoid was never released. Identifications of the parasitoids from south-western Kenya were based on morphological characters, allozyme frequencies, and mating experiments with laboratory populations of C. flavipes. It is hypothesized that C. flavipes became established from individuals escaping from a laboratory colony maintained in south-western Kenya in 1991.

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Photoperiod and some other factors affecting reproduction in female Sminthopsis crassicaudata (Gould) (Marsupialia : Dasyuridae) in captivity

Australian Journal of Zoology ◽

10.1071/zo9780449 ◽

1978 ◽

Vol 26 (3) ◽

pp. 449 ◽

Cited By ~ 17

Author(s):

MJ Smith ◽

JH Bennett ◽

CM Chesson

Keyword(s):

Widespread Species ◽

Factors Affecting ◽

Factors Influencing ◽

Pathological Conditions ◽

Sminthopsis Crassicaudata ◽

Laboratory Colony ◽

In Captivity ◽

Biochemical Variation ◽

To Come ◽

Short Days

In central and southern Australia, S. crassicaudata is a widespread species which shows morphological and biochemical variation throughout its range. A laboratory colony was established from wild-caught animals from central, southern and south-eastern populations. The origin of wild-caught females or the parentage of laboratory-bred females did not affect their response to any of the investigated factors influencing reproduction. Very few females produced litters after they had reached 30 months of age. The colony was maintained for nearly 10 years in one artificially illuminated room. The lighting schedule was usually 16L : 8D, but at approximately 6-monthly intervals the animals were subjected to 3 weeks of 8L : 16D. Significantly more litters were born in pairings that had experienced short days than in those continuously exposed to long days. Oestrous cycles ceased in the 8L : 16D periods and resumed at about 20-30 days after the onset of 16L : 8D in many females, although some took longer to come into oestrus. Two of 27 females did not come into oestrus within 88 days, and, of the 25 females that came into oestrus, five did not ovulate. Pathological conditions in the reproductive system were rare. Most litters were born within the first 6 weeks of pairs being formed. Females which had produced one litter were more likely to produce a second litter when returned to the father of their first litter than when caged with a different male. When two females were caged with one male, one or occasionally both females produced a litter. Breeding in response to onset of long days is not consistent with the opportunistic breeding of many desert animals.

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rpoS Mutations and Loss of General Stress Resistance in Escherichia coli Populations as a Consequence of Conflict between Competing Stress Responses

Journal of Bacteriology ◽

10.1128/jb.184.3.806-811.2002 ◽

2002 ◽

Vol 184 (3) ◽

pp. 806-811 ◽

Cited By ~ 167

Author(s):

Lucinda Notley-McRobb ◽

Thea King ◽

Thomas Ferenci

Keyword(s):

Escherichia Coli ◽

Nutrient Limitation ◽

Stress Responses ◽

Stress Resistance ◽

Acid Stress ◽

Selective Advantage ◽

General Stress ◽

Expression Of Genes ◽

Laboratory Populations ◽

External Stresses

ABSTRACT The general stress resistance of Escherichia coli is controlled by the RpoS sigma factor (φS), but mutations in rpoS are surprisingly common in natural and laboratory populations. Evidence for the selective advantage of losing rpoS was obtained from experiments with nutrient-limited bacteria at different growth rates. Wild-type bacteria were rapidly displaced by rpoS mutants in both glucose- and nitrogen-limited chemostat populations. Nutrient limitation led to selection and sweeps of rpoS null mutations and loss of general stress resistance. The rate of takeover by rpoS mutants was most rapid (within 10 generations of culture) in slower-growing populations that initially express higher φS levels. Competition for core RNA polymerase is the likeliest explanation for reduced expression from distinct promoters dependent on φ70 and involved in the hunger response to nutrient limitation. Indeed, the mutation of rpoS led to significantly higher expression of genes contributing to the high-affinity glucose scavenging system required for the hunger response. Hence, rpoS polymorphism in E. coli populations may be viewed as the result of competition between the hunger response, which requires sigma factors other than φS for expression, and the maintenance of the ability to withstand external stresses. The extent of external stress significantly influences the spread of rpoS mutations. When acid stress was simultaneously applied to glucose-limited cultures, both the phenotype and frequency of rpoS mutations were attenuated in line with the level of stress. The conflict between the hunger response and maintenance of stress resistance is a potential weakness in bacterial regulation.

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