Letteratura scientifica selezionata sul tema "Dasyuridae Reproduction"

Reproduction in female Antechinus minimus maritimus was investigated in the field and laboratory. Field data were obtained from a mark-recapture study. A laboratory colony was maintained to investigate the oestrous pattern, length of gestation and development of pouch young. Breeding occurred in winter with births in July or August. Gestation (mean � SD) was 30.6 � l.5 days for animals mated in the laboratory. Epithelial cells were present in the urine for 34.8 � 8.3 days, a lengthy period compared to A. stuartii (19.3 � 4.4 days). Ovaries from females before the breeding season contained small developing follicles. During the breeding season Graafian follicles (4-8 per ovary) or corpora lutea (4-13 per ovary) were found. Reproduction in A. m. maritimus females is similar to that described previously in other Antechinus.

'Stages in the spermatogenic cycle of Ningaui ridei, N. yvonneae and N. timealeyi are defined and the phenology of these stages is presented. In males of Ningaui spp. sexual maturity is reached in the first year, such that after the end of July of each year almost all male Ningaui spp. are considered reproductively mature. Male Ningaui spp. in the active spermatogenic phase are found during the entire season of births (August-January in N. ridei and N. timealeyi but perhaps terminating earlier in N. yvonneae); testes regress to an immature spermatogenic stage after January. There is no indication that in the field adult males die immediately following mating.

Observations on the pattern of reproduction in Sminthopsis longicaudata, at present considered to be an endangered species, are presented. S. longicaudata is polyoestrous and in the laboratory females are in breeding condition from late winter (August) to early summer (December). They enter oestrus up to four times during the breeding season. Two litters were born 17 and 19 days post-mating, but the gestation period may be less than 15 days. The mean length of the oestrous cycle is 34.4 days. Both males and females may be able to breed in more than one season.

Observations on reproduction in both wild-caught and laboratory-maintained Dasykaluta rosamondae have led to the conclusion that this species is one of 10 dasyurid marsupials in which males die soon after their first mating period. D. rosamondae have a short annual breeding season. The females are monoestrous, mating in September and bearing the young in November. Laboratory-reared young are weaned at an age of about 3 1/2-4 months, in February and March, and juveniles appear in the field population at this time. Both mates and females reach sexual maturity at an age of about 10 months. In the laboratory, males breed in only one season, after which those that survive become reproductively senile. Mature males disappear from the field population about the time the young are born; those collected shortly before this show signs of reproductive senescence. Males collected in the months after the young are weaned represent a single age-class; their reproductive development parallels that of maturing known-age males. Females are capable of breeding in at least two seasons and litters of up to eight are reared. Development of the pouch young is described. Unusual interstitial tissue masses develop in the ovaries of D. rosamondae; the granulosa cells of some follicles undergo transformation to interstitial cells, and the oocytes in these follicles degenerate, shortly before the females enter oestrus.

A laboratory colony of S. macroura, founded by three females and four males, was maintained over four breeding seasons. Reproductive success was high and four generations were produced before the colony was disbanded. Descendants of these animals are still breeding in another laboratory 11 years after the founding of the colony. A detailed prescription for the maintenance and management of a breeding colony is given. The animals bred between June and February, most females first entering oestrus in the early months of the season, in July or August. Female young born early in the season (before mid-October) matured in the season of their birth at an age of 86-159 days; those born later matured in the following season at an age of 185-262 days. In each group, those born later matured earlier. Minimum body weight at sexual maturity was 12.5 g. At least two litters can be reared in a season and individuals may breed in more than one season. S. macroura is polyoestrous with a mean cycle length of 23.25 days. The gestation period is about 11 days and up to eight young can be accommodated in the pouch. Lactating females may return to oesrrus up to 10 days before the young are weaned at 70 days old. Ovulation occurs spontaneously and the mean number of corpora lutea formed was 20.7. The corpora lutea reach maximal size late in pregnancy and they regress more rapidly in lactating than in non- lactating females. Up to three generations of corpora lutea could be recognised in the ovaries of females undergoing cycles uninterrupted by lactation. Changes In body weight, the pouch, and the gross and histological appearance of the reproductive tract were the same in pregnant and pseudopregnant females.

The breeding season of S. macroura extends from June to February, and individual males (both wild- caught and laboratory-reared) are capable of breeding over extended periods during the breeding season, and for up to three seasons, in the laboratory. Gross and histological changes in the reproductive organs and endocrine changes in relation to reproductive activity have been investigated. Males do not appear to reach sexual maturity until the season following that in which they were born, although spermatorrhoea may commence in the season of birth. Testis and epididymis weight of these males, which commence spermatorrhoea late in the season, approximates that of sexually mature males early in the season but androgen levels and the weight of the accessory glands are low in all males except during the early months of the season. The age at which spermatorrhoea commences ranges from 141 to 350 days. The minimum scrota1 width at which it commences is 7.9 mm and the minimum body weight, 14.0 g. The onset of spermatorrhoea is not a function of age or season and in S. macroura should be used with caution as an indicator of impending sexual maturity. Maximum corticosteroid- binding capacity (MCBC) generally exceeded corticosteroid concentration and no androgen-related fall in MCBC was evident.

Pseudantechinus macdonnellensis has a wide distribution within the arid zone of Australia. Observations have been made on reproduction in both newly captured and laboratory-maintained animals obtained from widely separated localities. They have a short annual breeding season; animals from the more westerly part of the range breed later in the year. Males are potentially capable of breeding in at least three seasons, and females in at least four. Females are monoestrous and the gestation period, timed from mating to birth, is from 45 to 55 days. The young are suckled for about 14 weeks in the laboratory and are capable of breeding in the season following that in which they were born, when they are approaching 1 year of age.

The ningbing antechinus is a species of small dasyurid marsupial found in the Kimberley region of Western Australia. Observations on reproduction have been made on newly captured and laboratory maintained specimens. The breeding season is short and mating occurs in June. The young are born after a long gestation, estimated to be between 45 and 52 days, in late July and early August. They are weaned in November when about 16 weeks old and they reach sexual maturity at 10-11 months, in the first breeding season after birth. Both males and females are potentially capable of breeding in a second season.

Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, Discipline of Ecology and Evolutionary Biology, 2008.
"March 2008" -- T.P. Includes author's previously published papers. Bibliography: pages 104-118. Also available in print form.

This thesis examines the reproductive biology of red-tailed phascogales, an obligate male semelparous dasyurid species, which is part of a captive breeding colony at Alice Springs Desert Park. The red-tailed phascogale belongs to a group of dasyurids that shows an unusual reproductive strategy amongst mammals, one which provides opportunity for understanding means by which individuals maximise their reproductive success and the role of sperm competition. The broad aim was to gain an understanding of the reproductive biology of red-tailed phascogales and explore means by which individuals can affect their reproductive success. Examination of the red-tailed phascogale reproductive biology showed that females mated with multiple males and were capable of storing sperm in their oviducts for at least a five day period. Captive female red-tailed phascogales showed greater plasticity in their breeding season than has been observed in Antechinus, which exhibits the same life history strategy. Females were observed to invest heavily into the production of young, producing almost twice as many ova (15.1 ± 1.9) as young they can raise and 76% of females filling six to eight of the eight available teats in a breeding attempt. A 63% male bias was observed in young attaching to the teats, which could be produced through differential attachment of the sexes to teats at birth. Of the 846 young born in the captive breeding colony, 68% were weaned, with weaning occurring between 90-110 days of age and a 53% female bias observed in young being weaned. By weaning, a litter of young weighed 380% of the mothers mass with male young tending to be heavier than females by weaning. No relationship was observed between maternal weight and either litter sex ratio or sex biased growth of young. A positive relationship between maternal body mass and body mass of offspring at weaning was observed, with the body mass of young at weaning correlated with its body mass at maturity. Multiple paternity was observed in more than half of the litters examined, with heavier males having increased siring success compared to lighter males. Genotyping showed that the effective population size for the captive colony was 1.9x that observed from the group managed studbook. Male reproduction was also not as tightly constrained as in Antechinus, with spermatogenic failure not occurring in captive populations until after mating had occurred, meaning males are not reliant on epididymal stores alone for successful breeding. Scrotal diameter showed a positive relationship with testis and epididymal mass across male life, although this relationship was not evident when analysis was restricted to the time of peak sperm production. Captive males showed the opposite pattern of testosterone fluctuations to that observed in wild animals, with lowest levels occurring during the mating period. Captive animals were able to survive up to five years in captivity, in contrast to the obligate semelparity observed in wild males. Although most captive females can survive to breed in a second year and females are known to breed in a second year in the wild, the reproductive strategy of females appears to be aimed at maximising the returns on their first breeding attempt. In males, the need to maximise the investment into the first breeding season is amplified through the complete absence of opportunity to breed again; either through post-mating mortality in the wild or spermatogenic failure in captivity. The results of this study have implications for captive breeding of red-tailed phascogales, with their reproductive biology; spermatogenic failure, restricted breeding season, teat number limiting the number of young raised, high lactational investment into young, sex biases, the need to maintain genetic diversity and biases in siring success; providing challenges for the maintenance of a captive population. The results of this study also provide comparative information that contributes to understanding the unusual life history strategy of Phascogale and Antechinus, and contributes to the growing body of knowledge about mating strategies in marsupials.
http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1330358
Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2008

This thesis examines the reproductive biology of red-tailed phascogales, an obligate male semelparous dasyurid species, which is part of a captive breeding colony at Alice Springs Desert Park. The red-tailed phascogale belongs to a group of dasyurids that shows an unusual reproductive strategy amongst mammals, one which provides opportunity for understanding means by which individuals maximise their reproductive success and the role of sperm competition. The broad aim was to gain an understanding of the reproductive biology of red-tailed phascogales and explore means by which individuals can affect their reproductive success. Examination of the red-tailed phascogale reproductive biology showed that females mated with multiple males and were capable of storing sperm in their oviducts for at least a five day period. Captive female red-tailed phascogales showed greater plasticity in their breeding season than has been observed in Antechinus, which exhibits the same life history strategy. Females were observed to invest heavily into the production of young, producing almost twice as many ova (15.1 ± 1.9) as young they can raise and 76% of females filling six to eight of the eight available teats in a breeding attempt. A 63% male bias was observed in young attaching to the teats, which could be produced through differential attachment of the sexes to teats at birth. Of the 846 young born in the captive breeding colony, 68% were weaned, with weaning occurring between 90-110 days of age and a 53% female bias observed in young being weaned. By weaning, a litter of young weighed 380% of the mothers mass with male young tending to be heavier than females by weaning. No relationship was observed between maternal weight and either litter sex ratio or sex biased growth of young. A positive relationship between maternal body mass and body mass of offspring at weaning was observed, with the body mass of young at weaning correlated with its body mass at maturity. Multiple paternity was observed in more than half of the litters examined, with heavier males having increased siring success compared to lighter males. Genotyping showed that the effective population size for the captive colony was 1.9x that observed from the group managed studbook. Male reproduction was also not as tightly constrained as in Antechinus, with spermatogenic failure not occurring in captive populations until after mating had occurred, meaning males are not reliant on epididymal stores alone for successful breeding. Scrotal diameter showed a positive relationship with testis and epididymal mass across male life, although this relationship was not evident when analysis was restricted to the time of peak sperm production. Captive males showed the opposite pattern of testosterone fluctuations to that observed in wild animals, with lowest levels occurring during the mating period. Captive animals were able to survive up to five years in captivity, in contrast to the obligate semelparity observed in wild males. Although most captive females can survive to breed in a second year and females are known to breed in a second year in the wild, the reproductive strategy of females appears to be aimed at maximising the returns on their first breeding attempt. In males, the need to maximise the investment into the first breeding season is amplified through the complete absence of opportunity to breed again; either through post-mating mortality in the wild or spermatogenic failure in captivity. The results of this study have implications for captive breeding of red-tailed phascogales, with their reproductive biology; spermatogenic failure, restricted breeding season, teat number limiting the number of young raised, high lactational investment into young, sex biases, the need to maintain genetic diversity and biases in siring success; providing challenges for the maintenance of a captive population. The results of this study also provide comparative information that contributes to understanding the unusual life history strategy of Phascogale and Antechinus, and contributes to the growing body of knowledge about mating strategies in marsupials.
Thesis (Ph.D.) - University of Adelaide, School of Earth and Environmental Sciences, 2008

Copies of author's previously published works, inserted.
Bibliography :p.137-167.
xi, 167, [54]p. leaves of plates : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Research performed on several aspects of the reproductive biology of the female, fat-tailed dunnarts (Sminthopsis crassicaudata). Investigates the origin of the shell membrane, the stage of embryonic development at which it is lost and implantation takes place, the morphological features of fetal-maternal cellular interactions at implantation and placentation.
Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomy and Histology, 1995

Copies of author's previously published articles inserted.
Bibliography: leaves 118-142.
vi, 156, [26] leaves, [22] leaves of plates : ill. (some col.) ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomy and Histology and Dept. of Animal Genetics, 1997?

Copies of author's previously published articles inserted.
Bibliography: leaves 118-142.
vi, 156, [26] leaves, [22] leaves of plates : ill. (some col.) ; 30 cm.
Thesis (Ph.D.)--University of Adelaide, Dept. of Anatomy and Histology and Dept. of Animal Genetics, 1997?

Predators with Pouches provides a unique synthesis of current knowledge of the world’s carnivorous marsupials—from Patagonia to New Guinea and North America to Tasmania. Written by 63 experts in each field, the book covers a comprehensive range of disciplines including evolution and systematics, reproductive biology, physiology, ecology, behaviour and conservation. Predators with Pouches reveals the relationships between the American didelphids and the Australian dasyurids, and explores the role of the marsupial fauna in the mammal community. It introduces the geologically oldest marsupials, from the Americas, and examines the fall from former diversity of the larger marsupial carnivores and their convergent evolution with placental forms. The book covers all aspects of carnivorous marsupials, including interesting features of life history, their unique reproduction, the physiological basis for early senescence in semelparous dasyurids, sex ratio variation and juvenile dispersal. It looks at gradients in nutrition—from omnivory to insectivory to carnivory—as well as distributional ecology, social structure and conservation dilemmas.