The Influence of Increased Photoperiod on Reproduction in the Dasyurid Marsupial, Sminthopsis crassicaudata

Female brown marsupial mice were mated and changes in the number and distribution of spermatozoa were assessed in several regions of the reproductive tract at 1, 2, 3, 7, 10, 14 and 18 days after mating. Approximately 40 x 10(3) spermatozoa/side were present in the female reproductive tract between Days 1 and 7 after a single mating. This had decreased (to approximately 9 x 10(3) spermatozoa/side) by Days 10 and 14 after mating; by Day 18 no spermatozoa were recovered. The maximum number of spermatozoa recorded in a female tract was approximately 72 x 10(3) spermatozoa/side (Day 5 female, death in laboratory) and the minimum recorded was approximately 2 x 10(3) spermatozoa/side on Day 2 after mating. Between Days 1 and 7 after mating most spermatozoa were located in the uterus and lower isthmus (isthmus 1) and spermatozoa were rarely found in the lateral vaginae. By 24 h after mating most spermatozoa (approximately 60%) were found in isthmus 1, but approximately 35% were still present in the uterus. Histological observations of the lower isthmus at this time showed that large numbers of spermatozoa were present in both the lumen of the duct and the sperm storage crypts which are located in this region. By Day 7 after mating approximately 91% of all spermatozoa in the female tract were in isthmus 1, most of these being confined to the sperm storage crypts. On Days 10 and 14 after mating almost all spermatozoa in the tract were in the crypt regions of isthmus 1 and on Day 18 degenerating spermatozoa were observed. No special orientation or association of spermatozoa in relation to crypt cells was observed. These results show that, although the number of spermatozoa inseminated is low by mammalian standards sperm transport in this species is extremely efficient and a large proportion of spermatozoa reaches the isthmus before ovulation (approximately 1 in 1 to 1 in 7). Several observations may explain the remarkable success of these low numbers of spermatozoa, including specializations of the reproductive tract which may have a directing effect on sperm movement and the special relationship which exists between spermatozoa and the oviducal environment which results in viable sperm storage. Recent observations suggest that an unusual sinusoidal mode of progressive motility observed in this species, may also influence the success of the low numbers of ejaculated spermatozoa.

Section: Mating Trialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Transport and storage of spermatozoa in the female reproductive tract of the brown marsupial mouse, Antechinus stuartii (Dasyuridae)

Taggart

Temple-Smith

1991

“…Oestrus was determined by the presence of cornified epithelial cells in urine samples (Godfrey, 1969;Selwood, 1985) collected 3 times per week during August.…”

Section: Mating Trialsmentioning

confidence: 99%

Effects of breeding season and mating on total number and distribution of spermatozoa in the epididymis of the brown marsupial mouse, Antechinus stuartii

Taggart¹,

Temple-Smith²

1990

Changes in the number and distribution of spermatozoa in the epididymis of the adult brown marsupial mouse were examined during July/August in mated and unmated males. The effects of mating on epididymal sperm populations were studied in 2 groups of males each mated 3 times and compared with the number and distribution of spermatozoa in the epididymides of 4 unmated control groups. One testis and epididymis were removed from each animal (hemicastration) either before or early in the mating season to provide information on initial sperm content and distribution. The contralateral side was removed later in the mating season to examine the effects of mating or sexual abstinence on epididymal sperm distribution. Epididymal sperm number peaked in both the distal caput and distal corpus/proximal cauda epididymidis in late July. The total number of spermatozoa, including those remaining in the testis, available to each male at the beginning of the mating season in early August was approximately 4.4 x 10(6)/side. Although recruitment of spermatozoa into the epididymis from the testis continued until mid-August, sperm content of the epididymis reached a peak of about 3.5 x 10(6)/epididymis in early August. At this time approximately 0.9 x 10(6) spermatozoa remained in the testis which had ceased spermatogenic activity. Throughout the mating season, epididymal spermatozoa were concentrated in the distal corpus/proximal cauda regions of the epididymis and were replenished by spermatozoa from upper regions of the duct. Relatively few spermatozoa were found in the distal cauda epididymidis, confirming a low sperm storage capacity in this region. A constant loss of spermatozoa from the epididymis, probably via spermatorrhoea, occurred throughout the mating season and very few spermatozoa remained in unmated males in late August before the annual male die-off. Mating studies showed that an average of 0.23 x 10(6) spermatozoa/epididymis were delivered per mating in this species, but the number of spermatozoa released at each ejaculation may be as few as 0.04 x 10(6)/epididymis when sperm loss via spermatorrhoea is taken into account. We suggest that the unusual structure of the cauda epididymidis, which has a very restricted sperm storage capacity, may function to limit the numbers of spermatozoa available at each ejaculation and thus conserve the dwindling epididymal sperm reserves in order to maximize the number of successful matings which are possible during the mating season.

“…A similar time interval is observed for mammals which mate in summer when housed in a long-day photoperiod; 37-100 days for cats (Dawson, 1941), 38-63 days for mares, 38-64 days for ferrets (Bissonette, 1932) and 35-77 days for the marsupial dasyurid, Sminthopsis crassicaudata (Godfrey, 1969). There would appear to be a requirement of approximately 50 days for the ovary to be primed for ovulation.…”

Section: Discussionmentioning

confidence: 59%

Influence of daylength on the initiation of the breeding season of the marsupial possum, Trichosurus vulpecula

Gemmell¹

1990

In Queensland, possums in the wild and in captivity first give birth during March and continue to give birth throughout the year until November. In this study the effect of short daylengths on the initiation of breeding activity was examined. One male and 4 female possums were transferred from an outside enclosure into a light control room (10 h light, 14 h dark) on 22 November. A control group of possums was housed in outside enclosures. The possums held in the light room gave birth 81.2 +/- 14.7 days (s.e.m.) after being placed in the short-day photoperiod. The control group gave birth 133.8 +/- 9.8 days after 22 November. This result suggests that photoperiod plays a role in the initiation of the breeding season of the brushtail possum.