Ovarian follicular superstimulation and oocyte maturation in the anoestrous southern hairy-nosed wombat, Lasiorhinus latifrons.

This study investigates the effect of three exogenous gonadotrophin regimens on ovarian follicular development in southern hairy-nosed wombats during the non-breeding season. Females were given either porcine follicle stimulating hormone (pFSH; total of 200 mg at 12 h intervals over 7 (Group 1), or 4 days (Group 2)), or pregnant mares' serum gonadotrophin (PMSG; single dose of 150 I.U. (Group 3)). In all treatment groups 25 mg of porcine luteinising hormone (pLH) was used to trigger maturation; Groups 1 and 2 received pLH 12 h after the final pFSH injection and Group 3 received pLH 72 h after PMSG. The results showed Group 1 produced significantly more follicles per ovary (5.91+/-1.28) than Group 2 (1.67+/-0.62), or Group 3 (2.17+/-1.16) at p<0.05. Control females received saline injections concurrently with the three treatment groups (n=6; 2 control animals for each treatment group). No follicular development occurred in any control female. Analysis of oocyte nuclear status revealed that while oocytes from all three treatment groups had resumed meiosis, only those in Group 1 (7-day pFSH/pLH treatment) progressed to metaphase II. These results have implications for the development of assisted breeding strategies in this species.

Pouch young removal and return to oestrus in wild southern hairy-nosed wombats (Lasiorhinus latifrons).

The southern hairy-nosed wombat (Lasiorhinus latifrons) is a seasonal breeding, burrowing marsupial adapted to a semi-arid environment and the closest relative of the endangered northern hairy-nosed wombat (Lasiorhinus krefftii). Females typically give birth to one to two young every 3 years with young weaned at 360-400 days. This study examined the occurrence of polyoestry in a wild population of southern hairy-nosed wombats, and in particular the ability of this species to produce additional offspring in the same breeding season if a young was prematurely lost or removed. Pouch young were removed during the breeding seasons of 1996/1997 and 2003. No females from the 1996 (n=3)/1997 (n=3) group gave birth to a second pouch young in the same breeding season. However, two females in this group gave birth to young the following season. In contrast, all the 2003 group of females (n=6) produced a second offspring in the same breeding season after removal of pouch young (RPY). The reason for the different response to RPY between the two groups is unknown. These studies confirm that southern hairy-nosed wombats are polyoestrus in the wild and are capable of producing more than one offspring in a single breeding season. Females that failed to return to oestrus in the breeding season that pouch young were removed bred again in the following season. Rapid replacement of southern hairy-nosed wombat pouch young in the same breeding season as RPY suggests that this procedure, linked to either hand-rearing or interspecific cross-fostering, should be seriously considered as a priority conservation action to increase the population size of the critically endangered sister species, the northern hairy-nosed wombat.

Effect of exogenous gonadotrophins on ovarian morphology and oocyte maturation in the southern hairy nosed wombat Lasiohinus latifrons during the breeding season.

The effect of the exogenous administration of porcine follicle-stimulating hormone (pFSH) and pregnant mare serum gonadotrophin (PMSG) on ovarian follicular development and oocyte maturation in the southern hairy nosed wombat Lasiorhinus latifrons was investigated. Three experimental groups were administered pFSH at various doses and for different treatment lengths, followed by 25 mg porcine luteinising hormone (pLH) 12 h after the last dose of pFSH. Another group was given PMSG followed 72 h later by 25 mg pLH. Animals were killed 24 h after pLH. The left ovary was fixed for histology and the morphology of the antral follicles was determined, whereas follicular oocytes in the right ovary were aspirated, fixed, stained with 42,62-diamidino-2-phenylindole, and viewed for nuclear maturation. There was no significant difference in the mean number of ovarian follicles >1 mm, or in the size class of follicles assessed between control and experimental groups. However, a trend was observed suggesting a possible increase in follicles >3.0 mm in experimental groups compared with control animals. In all females administered exogenous porcine gonadotrophins, but not controls, some of the mural granulosa cells of large tertiary antral follicles had markedly enlarged nuclei (approximately 14 microm in diameter). All oocytes from the control group remained at the germinal vesicle stage, whereas approximately 40% of oocytes retrieved from the pFSH groups and 82.4% retrieved from the PMSG-primed animals had undergone germinal vesicle break down, with a small number reaching meiosis II. The present study shows that exogenous administration of either pFSH or PMSG to hairy nosed wombats can induce follicular growth and oocyte maturation. Such findings could be useful in the development of reproductive technology in this species.

Oestrous cycle of captive southern hairy-nosed wombats (Lasiorhinus latifrons) in South Australia, Australia.

There is limited information available on the oestrous cycle of female southern hairy-nosed wombats (Lasiorhinus latifrons). This is mainly due to an extremely poor breeding success in captivity and the difficulty in routine recapturing of these cryptic, semi-fossorial animals in the wild. The aim of this study was to characterise the oestrous cycle of this species by monitoring peripheral plasma concentrations of progesterone and oestradiol, assessing changes in vaginal cytology, pouch condition and the urogenital sinus. Eight adult female wombats were monitored during the breeding season (July-December) over 2 years (2002-2003). Samples were collected up to three times a week. Vaginal smears contained several cell types, categorised by morphology, as either superficial epithelial cells or parabasal-intermediate cells. Leucocytes were also counted. Plasma progesterone profiles showed a mean oestrous cycle length of 36.33+/-0.67 days with a peak progesterone concentration of 139.53+/-10.62nmol/L. Levels of oestradiol peaked at a mean level of 467.33+/-44.32pmol/L on average 5 days before a rise in plasma progesterone values. The proportion of epithelial cells in vaginal smears varied throughout the cycle, with a high percentage of superficial epithelial cells observed during the follicular phase. During periods when progesterone concentrations were high, a greater percentage of parabasal-intermediate cells was observed. In conclusion, this study has characterised the oestrous cycle of the southern hairy-nosed wombat and confirmed that changes in vaginal smears together with pouch and urogenital sinus details could be used to determine signs of oestrus in this species.

The effects of habitat fragmentation on the social kin structure and mating system of the agile antechinus, Antechinus agilis.

Habitat fragmentation is one of the major contributors to the loss of biodiversity worldwide. However, relatively little is known about its more immediate impacts on within-patch population processes such as social structure and mating systems, whose alteration may play an important role in extinction risk. We investigated the impacts of habitat fragmentation due to the establishment of an exotic softwood plantation on the social kin structure and breeding system of the Australian marsupial carnivore, Antechinus agilis. Restricted dispersal by males in fragmented habitat resulted in elevated relatedness among potential mates in populations in fragments, potentially increasing the risk of inbreeding. Antechinus agilis nests communally in tree hollows; these nests are important points for social contact between males and females in the mating season. In response to elevated relatedness among potential mates in fragmented habitat, A. agilis significantly avoided sharing nests with opposite-sex relatives in large fragment sites (but not in small ones, possibly due to limited nest locations and small population sizes). Because opposite-sex individuals shared nests randomly with respect to relatedness in unfragmented habitat, we interpreted the phenomenon in fragmented habitat as a precursor to inbreeding avoidance via mate choice. Despite evidence that female A. agilis at high inbreeding risk selected relatively unrelated mates, there was no overall increased avoidance of related mates by females in fragmented habitats compared to unfragmented habitats. Simulations indicated that only dispersal, and not nonrandom mating, contributed to inbreeding avoidance in either habitat context. However, habitat fragmentation did influence the mating system in that the degree of multiple paternity was reduced due to the reduction in population sizes and population connectivity. This, in turn, reduced the number of males available to females in the breeding season. This suggests that in addition to the obvious impacts of reduced recruitment, patch recolonization and increased genetic drift, the isolation of populations in habitat patches may cause changes in breeding behaviour that contribute to the negative impacts of habitat fragmentation.